When working on RF circuits only a proper RF active probe such as 85024A (ideal) or 1152A or 54701A or etc....will work
forget about passive probes unless accurate amplitude measurement is not your concern and you just want to see the signal
even for that purpose sometimes passive probes load your oscillator (depending on where you probe it) such that it stops oscillating!
The total system bandwidth (probe + scope or SA) is the key parameter.
Anyways, how do you measure the 600MHz? Do you have the proper connector (SMB or SMC i forgot) and do you measure it with 50 Ohm SA?
There are a couple of MMIC ampifiers in the final stages of the 600MHz REF, I would check them for DC bias voltage, DC current draw and? temperature to see if they are dead
of course with an active RF probe you could check their gain.
I would still focus on the mixers, for now you can just inject a 600MHz into the second converter
because if the low band mixer or the second converter is dead they are very expensive to repair or replace specially the second converter used to cost a fortune as I recall
and you might find it beyond economic repair. the 600MHz ref is easy to repair and its cheap. those MMICs can be found on ebay and they are cheap
or you might conclude that the 1st and 2nd mixers are fine and there is a problem in the IF and log amp, that is usually easy and not expensive to repair.
toggle quoted message
Show quoted text
On Fri, Apr 12, 2019 at 08:11 PM, Dave Ireland wrote:
Amir
?
I think you are correct about the 100Mhz. I have become obsessed with the level without a proper method of measuring it. All the 300Mhz stuff following is working so can't be much wrong with it.
?
I am still however worried about the 600Mz level as this is being measured at the proper alignment point but another day dawns here in Australia and I have to leave it for a while.
?
Thanks for your help to date.
?
Dave
?
?
?
Sent from my Samsung GALAXY S5
-------- Original message --------
From: amirb <amir.borji@...>
Date: 13/04/2019 00:00 (GMT+08:00)
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP8560E Low Level
I still doubt that there is anything wrong with the ref osc and 600MHz lo, really. it could be just a measurement trap.
how are you measuring those 9dBm and 17dBm in-circuit amplitudes? remember that only and only a proper RF active probe?
with careful grounding can give you the correct value. Any passive probe even the best 500MHz passive probe will give you totally out of whack values. I have been there...
even with an active probe (cap <1-2pF) still the precise point at which you measure it, is very critical. If the 100MHz is like 10dB low I am sure
you would be getting errors because the PFD will probably fail to work and the loop becomes unlocked.?
Moreover, as you explained, even when you inject 600MHz Lo from the outside your second IF is still 24dB low. That has nothing to do?
with the ref osc anymore.
another thing that puzzled me is that when you inject 310.7MHz to the third converter you get a trace at -32dBm? it should be much higher, close to -10dBm I think.
(adjust your atten to 10dB and ref level to 0dBm) How is the level of 300MHz third converter LO drive??
your 'default' noise floor is too low (it must be around -65 to -70dB as I recall from the units that I had in the past)
usually that means a mixer is not working but it can have other reasons further down the signal path
On Fri, Apr 12, 2019 at 11:08 AM, Dave Ireland wrote:
John
?
Just some feed back. Tracked down the manufacturer of the crystal, Croven Crystals in Canada who are very helpful, and found the replacement crystal is the exact unit and even has the the HP number 0410-4065 lasered on the side where I didn't notice it.
?
Might just go away now and brush up on my oscillator theory to try to get more level so I can drive U700 with +9dBm instead of the -2dBm I have now.
?
Thanks for you assistance.
?
Dave
?
On 12/04/2019 5:27 pm, Dave Ireland wrote:
John
?
I am still back at U700 which seems to be working but I can't get enough drive into it.
?
The oscillator circuit is not tuning properly and I suspect it is the crystal. It has been changed sometime in the past and I not sure characteristics of the crystal are the same. I will see if I can trace? details of what has been put in it.
?
Thanks
?
Dave
?
?
?
On 12/04/2019 1:55 pm, johncharlesgord via Groups.Io wrote:
Dave,
I think I had an HP856x with a similar 600 MHz problem.? It turned out to be a failed RF amp on A15. (U501?? U701?? U702?)
--John Gord
On Thu, Apr 11, 2019 at 06:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for methodical fault finding techniques methinks.
?
Checking out the RF section block diagram, trying to follow your advice, I noticed the 600Mhz drive into the Second Converter. The 600Mhz is derived from the 100MHz VCXO that the regulator transistor had failed on. The 600MHz out of A15 is about 15dB low and when I injected 600Mhz at the right level into the second converter the level has come right up. Still about 20dB down but more promising.
?
I will go back now and go through the A15 board and get the outputs correct and then after that maybe check out A14 for the mixer and converter bias volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb wrote:
I forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing anymore, right? Any error message about Log amp or step gain amplifiers?
if there is no error and you are sure the attenuator and the input AC/DC coupling are ok (you can even check with oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem is by injecting signal at various points and measuring power levels according to the service manual
I dont think this is due to low LO amplitude in any of the converters. otherwise you would get an error message and besides
90dB down is way too much for that. I suspect this is due to a fault in one of the 3 converters or in the Log amp (but not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest you inject a signal at say -20 or -21dB to the first mixer (make sure span is set to zero)
and then measure the 310.7MHz second IF with an oscilloscope (I hope you have a 400-500MHz scope?) or even a power meter.
if the amplitude is way off then the problem is either the first mixer or the second converter. By the way, you can check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or -36dBm to the third IF input (you might have it on the front panel) (you must choose it first in the menus and also choose zero span)
and then you can measure the 10.7 Mhz final IF with an oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a HP8560E and until now have been doing well.
The unit on delivery had the classic distorted display and no apparent response to any input though it did sweep it was very slow. 12 Alarms were reported.
Choose the "600 MHz Reference Oscillator Unlocked" first and replacing failed 2N2222A regulator on the 100MHz oscillator which bought the display back and all the alarms disappeared. Best 40c I've ever spent.
Was it completely fixed? No unfortunately not, the input reads about 90dB low. Every thing else looks fine, the resolution band width, span and frequency accuracy all look good. Checked the attenuator and the filter and even went straight into the RF port on the first low band mixer but still 90dB down.
I am at an impass now until I can borrow a decent SA as I do not have anything to measure 3-6GHz.
I did the LO feed through test in the service manual ie centre freq 0Hz, Span 1MHz, input attenuator 0dB and it says the feed through should be between -6 and -30dBm. It says if it is inside this range the RF path following the Low band mixer is operating properly.
Mine is -26dBm, so in the range.
My question is does that test mean that the the Yig, the LO distribution amp, the first mixer LO and IF ports and all the following mixers are operating correctly albeit not 90dB out? If so, the only thing I can think is a faulty RF port on the mixer (sounds unlikely). Also, I suppose if the LO drive was low, maybe 10 dB or so, there would still be feed through but may be not enough level to bias the mixer to mix.
Any though while I wait for a better spec an?
Dave
?
?
?
?
|
Hi all,
have here a hp8640B how was OK in Amplitude and Frequency but Phase Lock was not possible and?when I listen with a SSB RX to the unmodulated carrier it has had a bad sound.
Unstable and rough sometimes jumping? a few kHz away. Why?
Watch the attached pdf file.
?
Listen to the sound now after solving the problem.
Good luck!
Armin
?
|
Re: Chinese test leads (Was: My $25 "In Poor Shape" 3468A has arrived)
On 4/12/19 9:41 PM, Bob Albert via Groups.Io wrote: I made my own Kelvin test leads from some of those Chinese clips.? The
clips are poorly designed and don't grip securely.? I flowed a bit of
solder over the ends of the tips and it's much better.
It may seem a travesty but I use these el cheapo clips on my HP 3456A
with success.? I made up a pair of leads and connect to the 4-wire Ohms
circuit.? I can now measure very low resistance.? I mean VERY low.? I
can measure the resistance of a? screwdriver shaft, for instance.
Now let's be reasonable.? How can one ever get along in life without
being able to measure the resistance of a screwdriver shaft? Chicks dig guys who can measure the resistance of a screwdriver shaft. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
Re: Chinese test leads (Was: My $25 "In Poor Shape" 3468A has arrived)
Well said, Bob! I tried my leads on my 3456A also. My screwdriver measures 3 milli-Ohms!
Jeremy
On Fri, Apr 12, 2019 at 6:41 PM Bob Albert via Groups.Io <bob91343= [email protected]> wrote:
I made my own Kelvin test leads from some of those Chinese clips.? The clips are poorly designed and don't grip securely.? I flowed a bit of solder over the ends of the tips and it's much better.
It may seem a travesty but I use these el cheapo clips on my HP 3456A with success.? I made up a pair of leads and connect to the 4-wire Ohms circuit.? I can now measure very low resistance.? I mean VERY low.? I can measure the resistance of a? screwdriver shaft, for instance.
Now let's be reasonable.? How can one ever get along in life without being able to measure the resistance of a screwdriver shaft?
Bob
On Friday, April 12, 2019, 6:26:05 PM PDT, Jeremy Nichols < jn6wfo@...> wrote:
I ordered two sets from the eBay supplier linked here. They just arrived (9 days after placing the order) and both work correctly. I am pleased.
Jeremy
I forgot to mention I had to do that as well. Just used a fine metal file to roughen up a spot so the solder would stick without having to heat them up too much.
The teeth on my clamps doesn't seem to have and conductivity problems, and clamps have a very firm grip.
On Thu, Apr 4, 2019 at 09:04 AM, J Mcvein wrote:
?
I did receive a set of those clips, and found it necessary to
solder the 4mm expansion sleeve/banana part to the base of
the plug so it doesn't spin and make poor contact.?
The meter will not zero otherwise.
?
JimMc
?
On Thursday, April 4, 2019, 7:59:10 AM PDT, Jeremy Nichols < jn6wfo@...> wrote: ?
?
I have a set on order and will report when they arrive.?
?
Jeremy?
?
On Wed, Apr 3, 2019 at 11:54 PM Tom Gardner < tggzzz@...> wrote: I bought some which look identical to that, and they didn't work. I demanded and
eventually got a refund.
The symptom was that on one of the leads, when measuring the resistance from one
4mm plug -> clamp -> 4mm plug, it looked effectively open circuit.
At first I presumed a wire was in place but not soldered properly, but the real
problem was that there was a coating on the clamp's "gold" teeth. Filing the
teeth resolved the problem, with the obvious downside.
On 04/04/19 03:58, Alex wrote:
> My chinese Kelvin test leads finally arrived, and they look & feel very good
> and solid. As usual my 3468A almost reads zero altough still a bit negative
> when I short them out. But I am pretty sure this problem will be solved very
> soon once I get something that is already in the mail.
>
> These cables took and extra week delay because of a post office mess-up on top
> of the several weeks it normally takes to get something from the far East. I
> am very glad I got these. Amazing build quality for only a bit under $9 and
> would highly recommend them to anyone.
>
>
- --
|
Re: Chinese test leads (Was: My $25 "In Poor Shape" 3468A has arrived)
I made my own Kelvin test leads from some of those Chinese clips.? The clips are poorly designed and don't grip securely.? I flowed a bit of solder over the ends of the tips and it's much better.
It may seem a travesty but I use these el cheapo clips on my HP 3456A with success.? I made up a pair of leads and connect to the 4-wire Ohms circuit.? I can now measure very low resistance.? I mean VERY low.? I can measure the resistance of a? screwdriver shaft, for instance.
Now let's be reasonable.? How can one ever get along in life without being able to measure the resistance of a screwdriver shaft?
Bob
On Friday, April 12, 2019, 6:26:05 PM PDT, Jeremy Nichols <jn6wfo@...> wrote:
I ordered two sets from the eBay supplier linked here. They just arrived (9 days after placing the order) and both work correctly. I am pleased.
Jeremy
I forgot to mention I had to do that as well. Just used a fine metal file to roughen up a spot so the solder would stick without having to heat them up too much.
The teeth on my clamps doesn't seem to have and conductivity problems, and clamps have a very firm grip.
On Thu, Apr 4, 2019 at 09:04 AM, J Mcvein wrote:
?
I did receive a set of those clips, and found it necessary to
solder the 4mm expansion sleeve/banana part to the base of
the plug so it doesn't spin and make poor contact.?
The meter will not zero otherwise.
?
JimMc
?
On Thursday, April 4, 2019, 7:59:10 AM PDT, Jeremy Nichols < jn6wfo@...> wrote: ?
?
I have a set on order and will report when they arrive.?
?
Jeremy?
?
On Wed, Apr 3, 2019 at 11:54 PM Tom Gardner < tggzzz@...> wrote: I bought some which look identical to that, and they didn't work. I demanded and
eventually got a refund.
The symptom was that on one of the leads, when measuring the resistance from one
4mm plug -> clamp -> 4mm plug, it looked effectively open circuit.
At first I presumed a wire was in place but not soldered properly, but the real
problem was that there was a coating on the clamp's "gold" teeth. Filing the
teeth resolved the problem, with the obvious downside.
On 04/04/19 03:58, Alex wrote:
> My chinese Kelvin test leads finally arrived, and they look & feel very good
> and solid. As usual my 3468A almost reads zero altough still a bit negative
> when I short them out. But I am pretty sure this problem will be solved very
> soon once I get something that is already in the mail.
>
> These cables took and extra week delay because of a post office mess-up on top
> of the several weeks it normally takes to get something from the far East. I
> am very glad I got these. Amazing build quality for only a bit under $9 and
> would highly recommend them to anyone.
>
>
-
|
Re: Chinese test leads (Was: My $25 "In Poor Shape" 3468A has arrived)
I ordered two sets from the eBay supplier linked here. They just arrived (9 days after placing the order) and both work correctly. I am pleased.
Jeremy
I forgot to mention I had to do that as well. Just used a fine metal file to roughen up a spot so the solder would stick without having to heat them up too much.
The teeth on my clamps doesn't seem to have and conductivity problems, and clamps have a very firm grip.
On Thu, Apr 4, 2019 at 09:04 AM, J Mcvein wrote:
?
I did receive a set of those clips, and found it necessary to
solder the 4mm expansion sleeve/banana part to the base of
the plug so it doesn't spin and make poor contact.?
The meter will not zero otherwise.
?
JimMc
?
On Thursday, April 4, 2019, 7:59:10 AM PDT, Jeremy Nichols < jn6wfo@...> wrote: ?
?
I have a set on order and will report when they arrive.?
?
Jeremy?
?
On Wed, Apr 3, 2019 at 11:54 PM Tom Gardner < tggzzz@...> wrote: I bought some which look identical to that, and they didn't work. I demanded and
eventually got a refund.
The symptom was that on one of the leads, when measuring the resistance from one
4mm plug -> clamp -> 4mm plug, it looked effectively open circuit.
At first I presumed a wire was in place but not soldered properly, but the real
problem was that there was a coating on the clamp's "gold" teeth. Filing the
teeth resolved the problem, with the obvious downside.
On 04/04/19 03:58, Alex wrote:
> My chinese Kelvin test leads finally arrived, and they look & feel very good
> and solid. As usual my 3468A almost reads zero altough still a bit negative
> when I short them out. But I am pretty sure this problem will be solved very
> soon once I get something that is already in the mail.
>
> These cables took and extra week delay because of a post office mess-up on top
> of the several weeks it normally takes to get something from the far East. I
> am very glad I got these. Amazing build quality for only a bit under $9 and
> would highly recommend them to anyone.
>
>
-
|
Re: HP 85044A T/R test set part - Cabinet Trim "zipper" - 08502-20007 - source or 3D printed copy?
Hi will the 3D printed ones be strong enough
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected][mailto: [email protected]] On Behalf Of David Feldman via Groups.Io Sent: 13 April 2019 02:03 To: [email protected]Subject: [HP-Agilent-Keysight-equipment] HP 85044A T/R test set part - Cabinet Trim "zipper" - 08502-20007 - source or 3D printed copy? In need of a pair of these plastic strips called "zipper", which I realized (after the fact) are how the two cabinet halves are held together (!). Is 3D printing a possible way to make these up? Thanks for any suggestions/info/ideas! Dave ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2016.0.8048 / Virus Database: 4793/15884 - Release Date: 08/14/18 Internal Virus Database is out of date.
|
HP 85044A T/R test set part - Cabinet Trim "zipper" - 08502-20007 - source or 3D printed copy?
In need of a pair of these plastic strips called "zipper", which I realized (after the fact) are how the two cabinet halves are held together (!).
Is 3D printing a possible way to make these up?
Thanks for any suggestions/info/ideas!
Dave
|
Amir
I think you are correct about the 100Mhz. I have become obsessed with the level without a proper method of measuring it. All the 300Mhz stuff following is working so can't be much wrong with it.
I am still however worried about the 600Mz level as this is being measured at the proper alignment point but another day dawns here in Australia and I have to leave it for a while.
Thanks for your help to date.
Dave
Sent from my Samsung GALAXY S5
toggle quoted message
Show quoted text
-------- Original message -------- From: amirb <amir.borji@...> Date: 13/04/2019 00:00 (GMT+08:00) To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP8560E Low Level I still doubt that there is anything wrong with the ref osc and 600MHz lo, really. it could be just a measurement trap. how are you measuring those 9dBm and 17dBm in-circuit amplitudes? remember that only and only a proper RF active probe? with careful grounding can give you the correct value. Any passive probe even the best 500MHz passive probe will give you totally out of whack values. I have been there... even with an active probe (cap <1-2pF) still the precise point at which you measure it, is very critical. If the 100MHz is like 10dB low I am sure you would be getting errors because the PFD will probably fail to work and the loop becomes unlocked.? Moreover, as you explained, even when you inject 600MHz Lo from the outside your second IF is still 24dB low. That has nothing to do? with the ref osc anymore. another thing that puzzled me is that when you inject 310.7MHz to the third converter you get a trace at -32dBm? it should be much higher, close to -10dBm I think. (adjust your atten to 10dB and ref level to 0dBm) How is the level of 300MHz third converter LO drive?? your 'default' noise floor is too low (it must be around -65 to -70dB as I recall from the units that I had in the past) usually that means a mixer is not working but it can have other reasons further down the signal path On Fri, Apr 12, 2019 at 11:08 AM, Dave Ireland wrote:
John
?
Just some feed back. Tracked down the manufacturer of the crystal, Croven Crystals in Canada who are very helpful, and found the replacement crystal is the exact unit and even has the the HP number 0410-4065 lasered on the side where I didn't notice it.
?
Might just go away now and brush up on my oscillator theory to try to get more level so I can drive U700 with +9dBm instead of the -2dBm I have now.
?
Thanks for you assistance.
?
Dave
?
On 12/04/2019 5:27 pm, Dave Ireland wrote:
John
?
I am still back at U700 which seems to be working but I can't get enough drive into it.
?
The oscillator circuit is not tuning properly and I suspect it is the crystal. It has been changed sometime in the past and I not sure characteristics of the crystal are the same. I will see if I can trace? details of what has been put in it.
?
Thanks
?
Dave
?
?
?
On 12/04/2019 1:55 pm, johncharlesgord via Groups.Io wrote:
Dave,
I think I had an HP856x with a similar 600 MHz problem.? It turned out to be a failed RF amp on A15. (U501?? U701?? U702?)
--John Gord
On Thu, Apr 11, 2019 at 06:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for methodical fault finding techniques methinks.
?
Checking out the RF section block diagram, trying to follow your advice, I noticed the 600Mhz drive into the Second Converter. The 600Mhz is derived from the 100MHz VCXO that the regulator transistor had failed on. The 600MHz out of A15 is about 15dB low and when I injected 600Mhz at the right level into the second converter the level has come right up. Still about 20dB down but more promising.
?
I will go back now and go through the A15 board and get the outputs correct and then after that maybe check out A14 for the mixer and converter bias volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb wrote:
I forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing anymore, right? Any error message about Log amp or step gain amplifiers?
if there is no error and you are sure the attenuator and the input AC/DC coupling are ok (you can even check with oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem is by injecting signal at various points and measuring power levels according to the service manual
I dont think this is due to low LO amplitude in any of the converters. otherwise you would get an error message and besides
90dB down is way too much for that. I suspect this is due to a fault in one of the 3 converters or in the Log amp (but not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest you inject a signal at say -20 or -21dB to the first mixer (make sure span is set to zero)
and then measure the 310.7MHz second IF with an oscilloscope (I hope you have a 400-500MHz scope?) or even a power meter.
if the amplitude is way off then the problem is either the first mixer or the second converter. By the way, you can check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or -36dBm to the third IF input (you might have it on the front panel) (you must choose it first in the menus and also choose zero span)
and then you can measure the 10.7 Mhz final IF with an oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a HP8560E and until now have been doing well.
The unit on delivery had the classic distorted display and no apparent response to any input though it did sweep it was very slow. 12 Alarms were reported.
Choose the "600 MHz Reference Oscillator Unlocked" first and replacing failed 2N2222A regulator on the 100MHz oscillator which bought the display back and all the alarms disappeared. Best 40c I've ever spent.
Was it completely fixed? No unfortunately not, the input reads about 90dB low. Every thing else looks fine, the resolution band width, span and frequency accuracy all look good. Checked the attenuator and the filter and even went straight into the RF port on the first low band mixer but still 90dB down.
I am at an impass now until I can borrow a decent SA as I do not have anything to measure 3-6GHz.
I did the LO feed through test in the service manual ie centre freq 0Hz, Span 1MHz, input attenuator 0dB and it says the feed through should be between -6 and -30dBm. It says if it is inside this range the RF path following the Low band mixer is operating properly.
Mine is -26dBm, so in the range.
My question is does that test mean that the the Yig, the LO distribution amp, the first mixer LO and IF ports and all the following mixers are operating correctly albeit not 90dB out? If so, the only thing I can think is a faulty RF port on the mixer (sounds unlikely). Also, I suppose if the LO drive was low, maybe 10 dB or so, there would still be feed through but may be not enough level to bias the mixer to mix.
Any though while I wait for a better spec an?
Dave
?
?
?
?
|
Re: Plastic snap-in bottom feet
Hi Stan
For the older equipment feet with a silver
button there are 3 different types of feet
?
The 432? has 2 feet one ?on the front and
one on the rear? both are the full width of the unit ??this unit is? 1/3 of a
bay width
?
The old 431 ?also has 2 feet one ?on the
front and one on the rear? both are the full width of the unit ??but this unit
is a ? ?bay width so feet are longer
?
The 141 had individual feet on each
corner?
?
Paul B
?
?
toggle quoted message
Show quoted text
On Fri, Apr 12, 2019 at 09:25 AM, <radioconnection@...>
wrote:
The older HP gear test gear feet were black, part number 5060-0767.
They had a metal push pin to allow side in installation or removal--found on
141T or similarly aged HP gear.
They are as rare as hen's teeth--few I have recently found were quite costly.
The excellent condition 432A power meter I just got has that style I
believe, and it actually still had the feet. This makes me even happier.
Sean
No virus found in this message.
Checked by AVG -
Version: 2016.0.8048 / Virus Database: 4793/15884 - Release Date: 08/14/18
Internal Virus Database is out of date.
|
Re: Plastic snap-in bottom feet
On Fri, Apr 12, 2019 at 09:25 AM, <radioconnection@...> wrote:
The older HP gear test gear feet were black, part number 5060-0767. They had a metal push pin to allow side in installation or removal--found on 141T or similarly aged HP gear.
They are as rare as hen's teeth--few I have recently found were quite costly.
The excellent condition 432A power meter I just got has that style I believe, and it actually still had the feet. This makes me even happier. Sean
|
Re: 141T varying CRT intensity?
On 04/12/2019 12:03 PM, radioconnection@... wrote: I've tried to troubleshoot this problem in the past, but whenever I have the unit opened up it has been well behaved.
The CRT intensity will vary (jump erratically) after the unit has been running for a few hours. I do not see any change in display size, blooming or in focus.
I have a new CRT on hand, and I am thinking about replacing most of the electrolytic capacitors and other parts that have a known history for failure
when I have a chance to work on the unit. Since it is on a high
shelf on the bench, getting it down is a bit of effort due to my age... so i want to do this once... any suggestions as to what to look for would be appreciated, since
just shotgunning and hoping for a repair isn't the best approach.
Thanks for any advice.
Pete It is almost certainly a heat problem, since it works OK when open to air. If you have a heat gun or a hair dryer, you might try to isolate an area where the problem is, but don't overdo it--those things get pretty hot! If you can isolate an area, then you might be able to pinpoint the bad part with a soldering iron. But remember, the soldering iron is probably grounded, so don't actually touch any circuit while the scope is running. Older soldering guns (Weller) were not grounded; I do not know if modern ones are. Check with your ohm-meter. --doug, WA2SAY
|
Re: Plastic snap-in bottom feet
If you have access to a 3d printer go to thingiverse dot com and look up HP foot, you may find what you are looking for.? I designed and printed some Tektronix pull tabs and got 50% yield using PLA and an Exact-O knife to trim them.? I used an Ultimaker 3+ to print them.
TinkerCAD and FreeCAD are no cost design tools. ?
Is anyone here machining circuit boards with a cheap RAMPS based controller?? I need to dead bug or circuit board a HP 8640 amplifier replacement.
Jim
On ?Friday?, ?April? ?12?, ?2019? ?12?:?26?:?01? ?PM? ?EDT, <radioconnection@...> wrote:
The older HP gear test gear feet were black, part number 5060-0767. They had a metal push pin to allow side in installation or removal--found on 141T or similarly aged HP gear.
They are as rare as hen's teeth--few I have recently found were quite costly.
The part numbers you mentioned will bring up images using Google search.? One looks like a screw mounted rear apron foot.? The other looks like a snap in gray bottom foot.
Peter
|
Re: Plastic snap-in bottom feet
The older HP gear test gear feet were black, part number 5060-0767. They had a metal push pin to allow side in installation or removal--found on 141T or similarly aged HP gear.
They are as rare as hen's teeth--few I have recently found were quite costly.
The part numbers you mentioned will bring up images using Google search.? One looks like a screw mounted rear apron foot.? The other looks like a snap in gray bottom foot.
Peter
|
141T varying CRT intensity?
I've tried to troubleshoot this problem in the past, but whenever I have the unit opened up it has been well behaved.?
The CRT intensity will vary (jump erratically) after the unit has been running for a few hours.? I do not see any change in display size, blooming or in focus.??
I have a new CRT on hand, and I am thinking about replacing most of the electrolytic capacitors and other parts that have a known history for failure
when I have a chance to work on the unit.? Since it is on a high
shelf on the bench, getting it down is a bit of effort due to my age...? so i want to do this once...? any suggestions as to what to look for would be appreciated, since
just shotgunning and hoping for a repair isn't the best approach.??
Thanks for any advice.
Pete
|
I still doubt that there is anything wrong with the ref osc and 600MHz lo, really. it could be just a measurement trap.
how are you measuring those 9dBm and 17dBm in-circuit amplitudes? remember that only and only a proper RF active probe?
with careful grounding can give you the correct value. Any passive probe even the best 500MHz passive probe will give you totally out of whack values. I have been there...
even with an active probe (cap <1-2pF) still the precise point at which you measure it, is very critical. If the 100MHz is like 10dB low I am sure
you would be getting errors because the PFD will probably fail to work and the loop becomes unlocked.?
Moreover, as you explained, even when you inject 600MHz Lo from the outside your second IF is still 24dB low. That has nothing to do?
with the ref osc anymore.
another thing that puzzled me is that when you inject 310.7MHz to the third converter you get a trace at -32dBm? it should be much higher, close to -10dBm I think.
(adjust your atten to 10dB and ref level to 0dBm) How is the level of 300MHz third converter LO drive??
your 'default' noise floor is too low (it must be around -65 to -70dB as I recall from the units that I had in the past)
usually that means a mixer is not working but it can have other reasons further down the signal path
toggle quoted message
Show quoted text
On Fri, Apr 12, 2019 at 11:08 AM, Dave Ireland wrote:
John
?
Just some feed back. Tracked down the manufacturer of the crystal, Croven Crystals in Canada who are very helpful, and found the replacement crystal is the exact unit and even has the the HP number 0410-4065 lasered on the side where I didn't notice it.
?
Might just go away now and brush up on my oscillator theory to try to get more level so I can drive U700 with +9dBm instead of the -2dBm I have now.
?
Thanks for you assistance.
?
Dave
?
On 12/04/2019 5:27 pm, Dave Ireland wrote:
John
?
I am still back at U700 which seems to be working but I can't get enough drive into it.
?
The oscillator circuit is not tuning properly and I suspect it is the crystal. It has been changed sometime in the past and I not sure characteristics of the crystal are the same. I will see if I can trace? details of what has been put in it.
?
Thanks
?
Dave
?
?
?
On 12/04/2019 1:55 pm, johncharlesgord via Groups.Io wrote:
Dave,
I think I had an HP856x with a similar 600 MHz problem.? It turned out to be a failed RF amp on A15. (U501?? U701?? U702?)
--John Gord
On Thu, Apr 11, 2019 at 06:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for methodical fault finding techniques methinks.
?
Checking out the RF section block diagram, trying to follow your advice, I noticed the 600Mhz drive into the Second Converter. The 600Mhz is derived from the 100MHz VCXO that the regulator transistor had failed on. The 600MHz out of A15 is about 15dB low and when I injected 600Mhz at the right level into the second converter the level has come right up. Still about 20dB down but more promising.
?
I will go back now and go through the A15 board and get the outputs correct and then after that maybe check out A14 for the mixer and converter bias volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb wrote:
I forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing anymore, right? Any error message about Log amp or step gain amplifiers?
if there is no error and you are sure the attenuator and the input AC/DC coupling are ok (you can even check with oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem is by injecting signal at various points and measuring power levels according to the service manual
I dont think this is due to low LO amplitude in any of the converters. otherwise you would get an error message and besides
90dB down is way too much for that. I suspect this is due to a fault in one of the 3 converters or in the Log amp (but not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest you inject a signal at say -20 or -21dB to the first mixer (make sure span is set to zero)
and then measure the 310.7MHz second IF with an oscilloscope (I hope you have a 400-500MHz scope?) or even a power meter.
if the amplitude is way off then the problem is either the first mixer or the second converter. By the way, you can check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or -36dBm to the third IF input (you might have it on the front panel) (you must choose it first in the menus and also choose zero span)
and then you can measure the 10.7 Mhz final IF with an oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a HP8560E and until now have been doing well.
The unit on delivery had the classic distorted display and no apparent response to any input though it did sweep it was very slow. 12 Alarms were reported.
Choose the "600 MHz Reference Oscillator Unlocked" first and replacing failed 2N2222A regulator on the 100MHz oscillator which bought the display back and all the alarms disappeared. Best 40c I've ever spent.
Was it completely fixed? No unfortunately not, the input reads about 90dB low. Every thing else looks fine, the resolution band width, span and frequency accuracy all look good. Checked the attenuator and the filter and even went straight into the RF port on the first low band mixer but still 90dB down.
I am at an impass now until I can borrow a decent SA as I do not have anything to measure 3-6GHz.
I did the LO feed through test in the service manual ie centre freq 0Hz, Span 1MHz, input attenuator 0dB and it says the feed through should be between -6 and -30dBm. It says if it is inside this range the RF path following the Low band mixer is operating properly.
Mine is -26dBm, so in the range.
My question is does that test mean that the the Yig, the LO distribution amp, the first mixer LO and IF ports and all the following mixers are operating correctly albeit not 90dB out? If so, the only thing I can think is a faulty RF port on the mixer (sounds unlikely). Also, I suppose if the LO drive was low, maybe 10 dB or so, there would still be feed through but may be not enough level to bias the mixer to mix.
Any though while I wait for a better spec an?
Dave
?
?
?
?
|
John
Just some feed back. Tracked down the
manufacturer of the crystal, Croven Crystals in Canada who are
very helpful, and found the replacement crystal is the exact unit
and even has the the HP number 0410-4065 lasered on the side where
I didn't notice it.
Might just go away now and brush up on
my oscillator theory to try to get more level so I can drive U700
with +9dBm instead of the -2dBm I have now.
Thanks for you assistance.
Dave
On 12/04/2019 5:27 pm, Dave Ireland
wrote:
toggle quoted message
Show quoted text
John
I am still back at U700 which seems
to be working but I can't get enough drive into it.
The oscillator circuit is not tuning
properly and I suspect it is the crystal. It has been changed
sometime in the past and I not sure characteristics of the
crystal are the same. I will see if I can trace? details of what
has been put in it.
Thanks
Dave
On 12/04/2019 1:55 pm,
johncharlesgord via Groups.Io wrote:
Dave,
I think I had an HP856x with a similar 600 MHz problem.? It
turned out to be a failed RF amp on A15. (U501?? U701?? U702?)
--John Gord
On Thu, Apr 11, 2019 at 06:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for
methodical fault finding techniques methinks.
?
Checking out the RF section block
diagram, trying to follow your advice, I noticed the 600Mhz
drive into the Second Converter. The 600Mhz is derived from
the 100MHz VCXO that the regulator transistor had failed on.
The 600MHz out of A15 is about 15dB low and when I injected
600Mhz at the right level into the second converter the
level has come right up. Still about 20dB down but more
promising.
?
I will go back now and go through
the A15 board and get the outputs correct and then after
that maybe check out A14 for the mixer and converter bias
volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb
wrote:
I
forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing
anymore, right? Any error message about Log amp or step
gain amplifiers?
if there is no error and you are sure the attenuator and
the input AC/DC coupling are ok (you can even check with
oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem
is by injecting signal at various points and measuring
power levels according to the service manual
I dont think this is due to low LO amplitude in any of the
converters. otherwise you would get an error message and
besides
90dB down is way too much for that. I suspect this is due
to a fault in one of the 3 converters or in the Log amp
(but not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest
you inject a signal at say -20 or -21dB to the first mixer
(make sure span is set to zero)
and then measure the 310.7MHz second IF with an
oscilloscope (I hope you have a 400-500MHz scope?) or even
a power meter.
if the amplitude is way off then the problem is either the
first mixer or the second converter. By the way, you can
check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or
-36dBm to the third IF input (you might have it on the
front panel) (you must choose it first in the menus and
also choose zero span)
and then you can measure the 10.7 Mhz final IF with an
oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a
HP8560E and until now have been doing well.
The unit on
delivery had the classic distorted display and no
apparent response to any input though it did sweep
it was very slow. 12 Alarms were reported.
Choose the "600 MHz
Reference Oscillator Unlocked" first and replacing
failed 2N2222A regulator on the 100MHz oscillator
which bought the display back and all the alarms
disappeared. Best 40c I've ever spent.
Was it completely
fixed? No unfortunately not, the input reads about
90dB low. Every thing else looks fine, the
resolution band width, span and frequency accuracy
all look good. Checked the attenuator and the filter
and even went straight into the RF port on the first
low band mixer but still 90dB down.
I am at an impass
now until I can borrow a decent SA as I do not have
anything to measure 3-6GHz.
I did the LO feed
through test in the service manual ie centre freq
0Hz, Span 1MHz, input attenuator 0dB and it says the
feed through should be between -6 and -30dBm. It
says if it is inside this range the RF path
following the Low band mixer is operating properly.
Mine is -26dBm, so
in the range.
My question is does
that test mean that the the Yig, the LO distribution
amp, the first mixer LO and IF ports and all the
following mixers are operating correctly albeit not
90dB out? If so, the only thing I can think is a
faulty RF port on the mixer (sounds unlikely). Also,
I suppose if the LO drive was low, maybe 10 dB or
so, there would still be feed through but may be not
enough level to bias the mixer to mix.
Any though while I
wait for a better spec an?
Dave
?
?
|
John
I am still back at U700 which seems to
be working but I can't get enough drive into it.
The oscillator circuit is not tuning
properly and I suspect it is the crystal. It has been changed
sometime in the past and I not sure characteristics of the crystal
are the same. I will see if I can trace? details of what has been
put in it.
Thanks
Dave
On 12/04/2019 1:55 pm, johncharlesgord
via Groups.Io wrote:
toggle quoted message
Show quoted text
Dave,
I think I had an HP856x with a similar 600 MHz problem.? It turned
out to be a failed RF amp on A15. (U501?? U701?? U702?)
--John Gord
On Thu, Apr 11, 2019 at 06:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for methodical
fault finding techniques methinks.
?
Checking out the RF section block
diagram, trying to follow your advice, I noticed the 600Mhz
drive into the Second Converter. The 600Mhz is derived from
the 100MHz VCXO that the regulator transistor had failed on.
The 600MHz out of A15 is about 15dB low and when I injected
600Mhz at the right level into the second converter the level
has come right up. Still about 20dB down but more promising.
?
I will go back now and go through
the A15 board and get the outputs correct and then after that
maybe check out A14 for the mixer and converter bias volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb
wrote:
I
forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing
anymore, right? Any error message about Log amp or step gain
amplifiers?
if there is no error and you are sure the attenuator and the
input AC/DC coupling are ok (you can even check with
oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem is
by injecting signal at various points and measuring power
levels according to the service manual
I dont think this is due to low LO amplitude in any of the
converters. otherwise you would get an error message and
besides
90dB down is way too much for that. I suspect this is due to
a fault in one of the 3 converters or in the Log amp (but
not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest
you inject a signal at say -20 or -21dB to the first mixer
(make sure span is set to zero)
and then measure the 310.7MHz second IF with an oscilloscope
(I hope you have a 400-500MHz scope?) or even a power meter.
if the amplitude is way off then the problem is either the
first mixer or the second converter. By the way, you can
check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or -36dBm
to the third IF input (you might have it on the front panel)
(you must choose it first in the menus and also choose zero
span)
and then you can measure the 10.7 Mhz final IF with an
oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a
HP8560E and until now have been doing well.
The unit on delivery
had the classic distorted display and no apparent
response to any input though it did sweep it was very
slow. 12 Alarms were reported.
Choose the "600 MHz
Reference Oscillator Unlocked" first and replacing
failed 2N2222A regulator on the 100MHz oscillator
which bought the display back and all the alarms
disappeared. Best 40c I've ever spent.
Was it completely
fixed? No unfortunately not, the input reads about
90dB low. Every thing else looks fine, the resolution
band width, span and frequency accuracy all look good.
Checked the attenuator and the filter and even went
straight into the RF port on the first low band mixer
but still 90dB down.
I am at an impass now
until I can borrow a decent SA as I do not have
anything to measure 3-6GHz.
I did the LO feed
through test in the service manual ie centre freq 0Hz,
Span 1MHz, input attenuator 0dB and it says the feed
through should be between -6 and -30dBm. It says if it
is inside this range the RF path following the Low
band mixer is operating properly.
Mine is -26dBm, so in
the range.
My question is does
that test mean that the the Yig, the LO distribution
amp, the first mixer LO and IF ports and all the
following mixers are operating correctly albeit not
90dB out? If so, the only thing I can think is a
faulty RF port on the mixer (sounds unlikely). Also, I
suppose if the LO drive was low, maybe 10 dB or so,
there would still be feed through but may be not
enough level to bias the mixer to mix.
Any though while I
wait for a better spec an?
Dave
?
?
|
Amir
If I input 100Mhz at -10dbm with 10dB
attenuator and zero span selected (setup for level measurements on
the RF path drawing) while injecting 600MHz at 0dBm (spec -3 to
+4.8)? into the LO of the second converter, I see 310.7Mhz at
-56dBm (diagram says -32dBm) out of second converter. If I use the
SA generated 600MHZ I see nothing at this same point.
If I inject 310.7MHz at -31dBm into the
RF of the third converter I get at a trace across the screen at
-32dBm.
I assume that means that there is a 20
odd dB loss some where in the Low Band Mixer or the Second
Converter. I assume that if the Yig or LO distribution amp was
20dB low, the Low Band Mixer wouldn't work through lack of drive
or I would get an alarm. The levels on the bias of the first mixer
are not exactly right and while the second converter 5v supplies
are not as accuarate as they could be the bias volts as stamped on
the unit are pretty close.
I think I will focus on the 600Mhz
first. The crystal in the 100Mhz oscillator has been changed at
some stage and when trying to peak the output level the maximum is
reached with the minimum capacitance of the trimmer. There is a
note on the circuit that the line tech should choose a inductance
to shunt the standard one across the crystal. There is no
additional inductor so I might play with this even though the
shunt is small, to see if I can get the trimmer to peak properly.
Yes mine is one of the later A15 boards with the 600Mhz derived
from the 100Mhz and while it gave me an alarm when the 100Mhz was
not there all, it says nothing when the level of the 100MHz and
hence the 600MHz is too low. Interestingly enough the 300MHz Cal
signal which is derived from the 100MHz also, is perfect but I see
there is a amp with AGC driving this output.?
With respect to the noise floor at full
span when I let it select every thing (1Mhz RBW) is -85dBm.
Thanks
Dave?
On 12/04/2019 12:12 pm, amirb wrote:
toggle quoted message
Show quoted text
sounds good :-)
so that means the second IF output (310.7MHz) must be almost dead.
Is it? It's a coaxial cable that goes to A15 board?
if the 600MHz is too low it cannot drive the x6 multiplier and
since there is a highly selective cavity filter at 3.6GHz
then the actual LO at the second mixer is pretty much non existent
which explains it.?
You must have one of the later models of A15 board. In older
models that I have also repaired, there was a 600MHz oscillator
which was in a PLL and when divided by 60 it was used as
reference? for the sampler circuit. So if the 600MHz was too low
you would get tons of errors both from sampler unlock and 600MHz
unlock. In later models, they have a 100MHz VCO in a PLL
so as long as that 100MHz is ok, you don't get any error for the
600MHz not being present or being too low.
since you are still 20dB too low, I would still suggest injecting
a clean 310.7MHz signal to the third converter at correct
amplitude (I think around -32dB or so)
and see what you get on screen
what is your noise floor at full span?
On Thu, Apr 11, 2019 at 09:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for methodical
fault finding techniques methinks.
?
Checking out the RF section block
diagram, trying to follow your advice, I noticed the 600Mhz
drive into the Second Converter. The 600Mhz is derived from
the 100MHz VCXO that the regulator transistor had failed on.
The 600MHz out of A15 is about 15dB low and when I injected
600Mhz at the right level into the second converter the level
has come right up. Still about 20dB down but more promising.
?
I will go back now and go through
the A15 board and get the outputs correct and then after that
maybe check out A14 for the mixer and converter bias volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb
wrote:
I
forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing
anymore, right? Any error message about Log amp or step gain
amplifiers?
if there is no error and you are sure the attenuator and the
input AC/DC coupling are ok (you can even check with
oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem is
by injecting signal at various points and measuring power
levels according to the service manual
I dont think this is due to low LO amplitude in any of the
converters. otherwise you would get an error message and
besides
90dB down is way too much for that. I suspect this is due to
a fault in one of the 3 converters or in the Log amp (but
not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest
you inject a signal at say -20 or -21dB to the first mixer
(make sure span is set to zero)
and then measure the 310.7MHz second IF with an oscilloscope
(I hope you have a 400-500MHz scope?) or even a power meter.
if the amplitude is way off then the problem is either the
first mixer or the second converter. By the way, you can
check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or -36dBm
to the third IF input (you might have it on the front panel)
(you must choose it first in the menus and also choose zero
span)
and then you can measure the 10.7 Mhz final IF with an
oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a
HP8560E and until now have been doing well.
The unit on delivery
had the classic distorted display and no apparent
response to any input though it did sweep it was very
slow. 12 Alarms were reported.
Choose the "600 MHz
Reference Oscillator Unlocked" first and replacing
failed 2N2222A regulator on the 100MHz oscillator
which bought the display back and all the alarms
disappeared. Best 40c I've ever spent.
Was it completely
fixed? No unfortunately not, the input reads about
90dB low. Every thing else looks fine, the resolution
band width, span and frequency accuracy all look good.
Checked the attenuator and the filter and even went
straight into the RF port on the first low band mixer
but still 90dB down.
I am at an impass now
until I can borrow a decent SA as I do not have
anything to measure 3-6GHz.
I did the LO feed
through test in the service manual ie centre freq 0Hz,
Span 1MHz, input attenuator 0dB and it says the feed
through should be between -6 and -30dBm. It says if it
is inside this range the RF path following the Low
band mixer is operating properly.
Mine is -26dBm, so in
the range.
My question is does
that test mean that the the Yig, the LO distribution
amp, the first mixer LO and IF ports and all the
following mixers are operating correctly albeit not
90dB out? If so, the only thing I can think is a
faulty RF port on the mixer (sounds unlikely). Also, I
suppose if the LO drive was low, maybe 10 dB or so,
there would still be feed through but may be not
enough level to bias the mixer to mix.
Any though while I
wait for a better spec an?
Dave
?
?
|
Dave,
I think I had an HP856x with a similar 600 MHz problem.? It turned out to be a failed RF amp on A15. (U501?? U701?? U702?)
--John Gord
toggle quoted message
Show quoted text
On Thu, Apr 11, 2019 at 06:16 PM, Dave Ireland wrote:
Amir
?
A lesson in the need for methodical fault finding techniques methinks.
?
Checking out the RF section block diagram, trying to follow your advice, I noticed the 600Mhz drive into the Second Converter. The 600Mhz is derived from the 100MHz VCXO that the regulator transistor had failed on. The 600MHz out of A15 is about 15dB low and when I injected 600Mhz at the right level into the second converter the level has come right up. Still about 20dB down but more promising.
?
I will go back now and go through the A15 board and get the outputs correct and then after that maybe check out A14 for the mixer and converter bias volts.
?
Thanks
?
Dave
?
?
On 11/04/2019 10:29 pm, amirb wrote:
I forgot to ask, what is your noise floor level at full span?
On Thu, Apr 11, 2019 at 10:27 AM, amirb wrote:
I assume there are no error messages appearing anymore, right? Any error message about Log amp or step gain amplifiers?
if there is no error and you are sure the attenuator and the input AC/DC coupling are ok (you can even check with oscilloscope by injecting a signal)
then the best and perhaps only way to isolate the problem is by injecting signal at various points and measuring power levels according to the service manual
I dont think this is due to low LO amplitude in any of the converters. otherwise you would get an error message and besides
90dB down is way too much for that. I suspect this is due to a fault in one of the 3 converters or in the Log amp (but not in any of the LO drives)
since you dont have a second spectrum analyzer, I suggest you inject a signal at say -20 or -21dB to the first mixer (make sure span is set to zero)
and then measure the 310.7MHz second IF with an oscilloscope (I hope you have a 400-500MHz scope?) or even a power meter.
if the amplitude is way off then the problem is either the first mixer or the second converter. By the way, you can check the mixer bias voltages coming from A14
In some versions even the first mixer has bias voltage.
Next you can inject a clean 310.7MHz at around -35 or -36dBm to the third IF input (you might have it on the front panel) (you must choose it first in the menus and also choose zero span)
and then you can measure the 10.7 Mhz final IF with an oscilloscope it must be around -15 to -17dBm I think.
On Thu, Apr 11, 2019 at 09:44 AM, Dave Ireland wrote:
I am repairing a HP8560E and until now have been doing well.
The unit on delivery had the classic distorted display and no apparent response to any input though it did sweep it was very slow. 12 Alarms were reported.
Choose the "600 MHz Reference Oscillator Unlocked" first and replacing failed 2N2222A regulator on the 100MHz oscillator which bought the display back and all the alarms disappeared. Best 40c I've ever spent.
Was it completely fixed? No unfortunately not, the input reads about 90dB low. Every thing else looks fine, the resolution band width, span and frequency accuracy all look good. Checked the attenuator and the filter and even went straight into the RF port on the first low band mixer but still 90dB down.
I am at an impass now until I can borrow a decent SA as I do not have anything to measure 3-6GHz.
I did the LO feed through test in the service manual ie centre freq 0Hz, Span 1MHz, input attenuator 0dB and it says the feed through should be between -6 and -30dBm. It says if it is inside this range the RF path following the Low band mixer is operating properly.
Mine is -26dBm, so in the range.
My question is does that test mean that the the Yig, the LO distribution amp, the first mixer LO and IF ports and all the following mixers are operating correctly albeit not 90dB out? If so, the only thing I can think is a faulty RF port on the mixer (sounds unlikely). Also, I suppose if the LO drive was low, maybe 10 dB or so, there would still be feed through but may be not enough level to bias the mixer to mix.
Any though while I wait for a better spec an?
Dave
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Armin Roesch
Dave McGuire
Jeremy Nichols
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