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Date
5342A: blown sampler?

 

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Hi all,
one of my other projects I'm working on is a 5342A which does not count on the high frequency input.
I checked the sampler according to the service manual. I used a 34401A for the resistance meausrement and got 22k in forward bias and >3M in reverse bias. This is quite different from the values stated in the service manual; however, when I look at the schematic, I think it should be possible to test the sampler with the diode test function. I did that, and I found out that in forward bias, I have approx. 0.4 volts, and reverse bias is open. So it looks like a pretty nice diode. However I cannot compare to other samplers, and the service manual also tells that the resistance measured can vary greatly if not exact 1mA measuring current is used.
Does that sampler look good to you guys, or is it probably broken? because if it is broken I think it makes no sense to invest additional time to fix things.

Tobias, HB9FSX
Re: Plan to deep cleaning my gear

 

开云体育

Hi Calvin

My recommendation is you just dust equipment out clean edge connectors and service fan assemblies / motors / bearings

In short if it is not broken do not fix it I only use soap and water on cases

听

I would never do a deep clean as you describe with any of my 50 plus hp items

For sticking keyboards I disassemble them to clean them

Regards Paul B

From: hp_agilent_equipment@... [mailto:hp_agilent_equipment@...]
Sent: 16 October 2017 05:27
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Plan to deep cleaning my gear

Hi,

I am thinking of deep cleaning of my gear. 8566 SA, 8510 VNA, 8515A S-parameter test set, 8350/83592 sweeper.

I think I am going to remove all PCBs, soak them into clean water, brush them and dry them with hair dryer as soon as I can.

For delicate microwave assemblies like DC, YIG, YTFM, mixer and ovenized crystal, and CRT display, I will just brush dirt off the surface and leave them alone.

For sticky keys, soak the keyboard assembly into IPA, rinse them and dry them as quickly as I could.

Sounds like a plan?

Thank you!

Calvin._,_.___

Posted by: Calvin Guan

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Re: Plan to deep cleaning my gear

 

Just be careful about possible water ingress at the edges of the fiber glass boards. It can actually cause some problems with high impedance circuits (Been there...) I would use an ordinary oven and set it to ... 50-60 Degrees Celsius and put the boards in there for about an hour.


BR


Ulf Kylenfall - SM6GXV
Re: YIG device failure modes

 

开云体育

I regularly check eBay for spare parts list as 鈥渨orking鈥�. Just keep looking. You would get what you want one day.

Calvin

On Oct 15, 2017, at 9:44 PM, Tobias Pluess tobias.pluess@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:

Jeff,

re-fitting a different YIG was an option which I was thinking about when I repaired my 8341A sweeper. The YIG is a 5086-7323 which operates from 2.3 to 7GHz and tuning coil sensitivity is 24mA/GHz. However, I wonder how accurate those 24mA/GHz are. For instance, if I fitted another YIG with 20mA/GHz, would that work as well? the YO driver used can be calibrated for offset and gain... Have you ever fitted a replacement YIG?
What about those SYTMs HP has used sometimes (switchable YIG tuned multiplier)? is there any replacement?
And do you have an idea what the reason could be for the semiconductor to fail? assuming the operating voltages were ok, is there some chemical aging process or so which destroys the semiconductor some day? because there are instruments which are 30 yrs old and still working, but the older they get the more difficult it will be to find spare parts I guess; if the YIG fails and cannot be replaced, the whole instrument is nothing more than a really heavy paperweight....

Tobias HB9FSX



-------- Original message --------
From: "kmec@...听[hp_agilent_equipment]" <hp_agilent_equipment@...>
Date: 10/16/17 06:01 (GMT+01:00)听
Subject: Re: [hp_agilent_equipment] YIG device failure modes听

听

I have tested several hundred YIG devices over my career. (Have drawers full of them, its a sickness)听 I have seen more misaligned YIG support rods or bad oscillator semiconductors than I have seen bad coils.
听
Sometimes the coil connection fails at the solder point due to wire wrap/crimp failure and current heating the joint, eventually it opens, have fixed three like this. Some model YIGs have high coil current and if poorly cooled/heatsunk, the enamel insulation seems to fail and create a sorted coil. Only have seen one like this, but opened it up and figured out the failure.
听
Other times, the polystyrene rod that holds the YIG sphere warps & twists over time from heat听& general plasticizer failure听and misaligns the magnetic axis of the sphere with the field, pretty tough to fix this, major cause of holes and high end tailing off.听
And, of course, when the semiconductor device fails (Gunn diode in older X band and up, Bipolar thru 12 GHz for old ones, FET now), you are done.
听
It is possible to re-fit different YIGs into various pieces of gear, but re-scaling the drivers to the right coil sensitivities can be challenging/time-consuming.
听
The worst thing to deal with is the wideband听 YIG tuned multipliers. Never had much luck bringing these back to life once they go south.
听
YMMV
Jeff Kruth
WA3ZKR
听
In a message dated 10/15/2017 1:40:13 P.M. Eastern Daylight Time,听hp_agilent_equipment@...听writes:
听

Hi guys. Over the years I have read a lot about yigs going bad specifically their coils seem to go bad. Is there anything that can be done pre-emptively to secure their longevity? And what exactly happens? Do the coils open due to excessive current (like a fuse?) I know there is an issue where the sphere sometimes moves and gets located incorrectly IIRC. I don鈥檛 know what causes that, perhaps excessive force? But I am interested in the coil issue. I have no yig issues at the moment, which seems like a good time to try to prevent it?


Eugene W2HX
Re: Plan to deep cleaning my gear

 

As a fan of cleaning old electronics I would make a few comments:
Look at a number of past threads on cleaning,
Not everything really needs total cleaning, some things should not be
"cleaned" and some labels can be removed with water. Other things need to be
cleaned but can't be cleaned with water/soap (such as HP clear vinyl tubing
in power supplies)
Start off with some things that are worth less.
To really get stuff off, you will need a surfactant but surfactants can
remove labels and other marks so you have to be careful what and where.
I would not soak pcbs, that can get a lot of water into stuff like pots, and
transformers, carefully brush and hose off with water. Avoiding
spraying/soaking into stuff like pots and transformers.
I would not "dry" with a hairdryer too hot too quick, blow off as much water
(taking as much dissolved salts) as you can with lots of cold air, I use a
clean leaf blower on at night when there is lots of water in the air(no
static).
Then possibly rewash, reblow, rewash and reblow (triple rinse)
Then dry in a 120F ish temp with some air movement for 24 or more hours.
I have used an old fruit dehydrator, worked great, that died from too much
use, Now I have been using an oven with a 50W bulb and small crack in door
where cord goes in (gets just to 115F)
Take lots of pictures before things are taken apart, saved me many a time

Just some thoughts
John

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]
Sent: Sunday, October 15, 2017 9:27 PM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Plan to deep cleaning my gear

Hi,

I am thinking of deep cleaning of my gear. 8566 SA, 8510 VNA, 8515A
S-parameter test set, 8350/83592 sweeper.

I think I am going to remove all PCBs, soak them into clean water, brush
them and dry them with hair dryer as soon as I can.

For delicate microwave assemblies like DC, YIG, YTFM, mixer and ovenized
crystal, and CRT display, I will just brush dirt off the surface and leave
them alone.

For sticky keys, soak the keyboard assembly into IPA, rinse them and dry
them as quickly as I could.

Sounds like a plan?

Thank you!

Calvin

------------------------------------
Posted by: Calvin Guan <guancalvin@...>
------------------------------------


------------------------------------

Yahoo Groups Links
Re: Plan to deep cleaning my gear

 

开云体育

Hi
I would not soak the PCBs. Just blow away dirt using air. Somewhere I once read that the laminate of the PCBs can sponge up the water and I don't know whether this is nice. Better not to try it, your instruments are too nice to destroy them by cleaning :-) if it was a PCB from something really ordinary, I would give it a try, but for sure not with those gems! ;-)

Tobias


-------- Original message --------
From: "Calvin Guan guancalvin@... [hp_agilent_equipment]"
Date: 10/16/17 06:27 (GMT+01:00)
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Plan to deep cleaning my gear

听

Hi,

I am thinking of deep cleaning of my gear. 8566 SA, 8510 VNA, 8515A S-parameter test set, 8350/83592 sweeper.

I think I am going to remove all PCBs, soak them into clean water, brush them and dry them with hair dryer as soon as I can.

For delicate microwave assemblies like DC, YIG, YTFM, mixer and ovenized crystal, and CRT display, I will just brush dirt off the surface and leave them alone.

For sticky keys, soak the keyboard assembly into IPA, rinse them and dry them as quickly as I could.

Sounds like a plan?

Thank you!

Calvin
Re: YIG device failure modes

 

开云体育

Jeff,
re-fitting a different YIG was an option which I was thinking about when I repaired my 8341A sweeper. The YIG is a 5086-7323 which operates from 2.3 to 7GHz and tuning coil sensitivity is 24mA/GHz. However, I wonder how accurate those 24mA/GHz are. For instance, if I fitted another YIG with 20mA/GHz, would that work as well? the YO driver used can be calibrated for offset and gain... Have you ever fitted a replacement YIG?
What about those SYTMs HP has used sometimes (switchable YIG tuned multiplier)? is there any replacement?
And do you have an idea what the reason could be for the semiconductor to fail? assuming the operating voltages were ok, is there some chemical aging process or so which destroys the semiconductor some day? because there are instruments which are 30 yrs old and still working, but the older they get the more difficult it will be to find spare parts I guess; if the YIG fails and cannot be replaced, the whole instrument is nothing more than a really heavy paperweight....

Tobias HB9FSX



-------- Original message --------
From: "kmec@... [hp_agilent_equipment]"
Date: 10/16/17 06:01 (GMT+01:00)
To: hp_agilent_equipment@...
Subject: Re: [hp_agilent_equipment] YIG device failure modes

听

I have tested several hundred YIG devices over my career. (Have drawers full of them, its a sickness)听 I have seen more misaligned YIG support rods or bad oscillator semiconductors than I have seen bad coils.
听
Sometimes the coil connection fails at the solder point due to wire wrap/crimp failure and current heating the joint, eventually it opens, have fixed three like this. Some model YIGs have high coil current and if poorly cooled/heatsunk, the enamel insulation seems to fail and create a sorted coil. Only have seen one like this, but opened it up and figured out the failure.
听
Other times, the polystyrene rod that holds the YIG sphere warps & twists over time from heat听& general plasticizer failure听and misaligns the magnetic axis of the sphere with the field, pretty tough to fix this, major cause of holes and high end tailing off.
And, of course, when the semiconductor device fails (Gunn diode in older X band and up, Bipolar thru 12 GHz for old ones, FET now), you are done.
听
It is possible to re-fit different YIGs into various pieces of gear, but re-scaling the drivers to the right coil sensitivities can be challenging/time-consuming.
听
The worst thing to deal with is the wideband听 YIG tuned multipliers. Never had much luck bringing these back to life once they go south.
听
YMMV
Jeff Kruth
WA3ZKR
听
In a message dated 10/15/2017 1:40:13 P.M. Eastern Daylight Time, hp_agilent_equipment@... writes:
听

Hi guys. Over the years I have read a lot about yigs going bad specifically their coils seem to go bad. Is there anything that can be done pre-emptively to secure their longevity? And what exactly happens? Do the coils open due to excessive current (like a fuse?) I know there is an issue where the sphere sometimes moves and gets located incorrectly IIRC. I don鈥檛 know what causes that, perhaps excessive force? But I am interested in the coil issue. I have no yig issues at the moment, which seems like a good time to try to prevent it?

Eugene W2HX

Plan to deep cleaning my gear

 

Hi,

I am thinking of deep cleaning of my gear. 8566 SA, 8510 VNA, 8515A S-parameter test set, 8350/83592 sweeper.

I think I am going to remove all PCBs, soak them into clean water, brush them and dry them with hair dryer as soon as I can.

For delicate microwave assemblies like DC, YIG, YTFM, mixer and ovenized crystal, and CRT display, I will just brush dirt off the surface and leave them alone.

For sticky keys, soak the keyboard assembly into IPA, rinse them and dry them as quickly as I could.

Sounds like a plan?

Thank you!

Calvin
Re: YIG device failure modes

 

开云体育

I have tested several hundred YIG devices over my career. (Have drawers full of them, its a sickness)听 I have seen more misaligned YIG support rods or bad oscillator semiconductors than I have seen bad coils.
听
Sometimes the coil connection fails at the solder point due to wire wrap/crimp failure and current heating the joint, eventually it opens, have fixed three like this. Some model YIGs have high coil current and if poorly cooled/heatsunk, the enamel insulation seems to fail and create a sorted coil. Only have seen one like this, but opened it up and figured out the failure.
听
Other times, the polystyrene rod that holds the YIG sphere warps & twists over time from heat听& general plasticizer failure听and misaligns the magnetic axis of the sphere with the field, pretty tough to fix this, major cause of holes and high end tailing off.
And, of course, when the semiconductor device fails (Gunn diode in older X band and up, Bipolar thru 12 GHz for old ones, FET now), you are done.
听
It is possible to re-fit different YIGs into various pieces of gear, but re-scaling the drivers to the right coil sensitivities can be challenging/time-consuming.
听
The worst thing to deal with is the wideband听 YIG tuned multipliers. Never had much luck bringing these back to life once they go south.
听
YMMV
Jeff Kruth
WA3ZKR
听
In a message dated 10/15/2017 1:40:13 P.M. Eastern Daylight Time, hp_agilent_equipment@... writes:

听

Hi guys. Over the years I have read a lot about yigs going bad specifically their coils seem to go bad. Is there anything that can be done pre-emptively to secure their longevity? And what exactly happens? Do the coils open due to excessive current (like a fuse?) I know there is an issue where the sphere sometimes moves and gets located incorrectly IIRC. I don鈥檛 know what causes that, perhaps excessive force? But I am interested in the coil issue. I have no yig issues at the moment, which seems like a good time to try to prevent it?

Eugene W2HX
Re: 3585B Spectrum Analyzer

[email protected]
 

Good tip Peter. I'll keep that in mind.

Thanks, Peter
ve3poa
Re: 8568B YTO unlocked

 

开云体育

On my 8566b, if the span is greater than certain MHz, the sweep source is operate in 鈥淟ock and Roll鈥� mode - locks to the sweep start frequency then applies a ramp to roll.

Calvin

On Oct 15, 2017, at 11:34 AM, edbreya@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:

听

I don't know about the screen flickering, but I do think the YTO loop behavior is normal. At wider spans it is not constantly phase-locked - it is driven open-loop with fairly accurate sweep current, and I think possibly re-phase-locked just at the beginning of the sweep each time around. For wide spans, you can't resolve the small frequency error on-screen anyway, but for narrow ones, more stability is needed, so the LO is locked. It's also possible that the narrow spans instead fix the first LO and use the second LO for sweeping - I can't recall for sure, but it should be one of those two schemes.

Definitely get the manual if you haven't already.

Ed
Re: HP 60鈥檚 Front Panel Color

 

开云体育

For myself, I use Sherwin Williams. 听You need a small sample of the color. 听Roughly an inch and a half square and they will match it exactly. 听They will mix an industrial enamel in batches as small as a quart and can supply it as gloss, semi-gloss, satin, or flat. 听I have produced absolutely invisible small spot touch ups. 听I would think there would be an equivalent supplier in the UK.

George


Sent from my T-Mobile 4G LTE Device

-------- Original message --------
From: "Adrian Nicol fenland787a@... [hp_agilent_equipment]" <hp_agilent_equipment@...>
Date: 10/15/17 1:50 PM (GMT-05:00)
To: hp_agilent_equipment@...
Subject: Re: [hp_agilent_equipment] HP 60鈥檚 Front Panel Color

听

Hi, I'm not sure there is an exact match in the RAL pallet. The nearest I have found for instruments of that vintage is RAL7042. That looks ok for panels that I wanted to 'tone in' with the HP equipment but it is probably not close enough to invisibly touch-up parts of an existing original panel. I have not explored it yet, but I gather there are now companies around who will colour (or color!) match from a sample and then mix an exact match for you. Some will do this in modest volume and for a reasonable cost, or so I am told!

Adrian


On Sunday, October 15, 2017 5:41 PM, "mmaseda@... [hp_agilent_equipment]" <hp_agilent_equipment@...> wrote:


听
Can some please share with me the paint code used by HP for front panels in the 60鈥檚? 听I have a very early 410C I鈥檓 trying to redo. 听The color is more dark than the RAL7044 used on the later 410C meters.
Re: Restoring HP 1740A scope, strange waveforms seen, assistance please?

[email protected]
 

Hi everyone, many thanks for the tips and pointers, especially the one from Dave. I checked the switch contact, 1D is the only extra switch being used on all ranges from 0.5V upto and including 20V per div and this checked out just fine.听

Further investigation on the input for Channel A showed that R3 should be 990k but was reading 11M so there was the culprit. Problem being this resistor sits in what appears to be a metal shield which soldered to the ground plane and is also shown on the component map as MP1? This resistor sits across a isolation slot so I'm guessing that is meant to be providing extra protection against stuffing over voltage into the channel via the probe and the shield is contain any flash, is that right?

Anyway, purely as a test I have soldered a 1M resistor across it and tested it and it works fine so I'll need to replace it with the correct rating and stuff it back into the shield?

The other issue I have is that the delay timebase knob has broken up and left the brass boss on the shaft which I cannot get off as the grub screw just chews up the allen key head all the time. So does anyone know where I can get new knobs for the time base (both knobs) and both of the shafts as I see thats the best solution to the boss problem and there are missing grub screws so a set of knobs with them fitted seems the best option if possible.
Re: HP items for sale

 

Hi Frank,

I抦 interested in the 3400A depending upon the serial number prefix. If you could be so kind as to let me know.

Thanks,

Dave W6TE

Sent from Mail<> for Windows 10

From: Frank Hughes hp_ciscovss@... [hp_agilent_equipment]<mailto:hp_agilent_equipment@...>
Sent: Sunday, October 15, 2017 1:27 PM
To: Yahoo! Inc.<mailto:hp_agilent_equipment@...>
Subject: [hp_agilent_equipment] HP items for sale


Hi,
I'm having trouble lifting heavy things now (surgery on both rotator cuffs), and the son will soon complete his Computer Engineering degree, move away, and then I'll try to move these and be scolded (again) by the surgeon.
Let me know if you want photos. All work, unless noted.

I realize the shipping costs for the heavy things make them less attractive, but trying here first.
Located in central Fla. Bring a chain saw.....

Thanks and 73
Frank Hughes
KJ4OLL

HP 6521A 0-1kv DC, 0-200ma, 110vac input $100 plus shipping
HP 6268B 0-40vdc, 0-30A, 240vac input $250 plus shipping
Harrison 6267A, 0-36vdc, 0-10A, 110 vac input, amp meter does not work. $50 plus shipping
Harrison 6367A 0-36vdc, 0-10A, 110 vac input, $50 plus shipping
HP 6434B 0-40vdc, 0-25A, 110 vac input $150 plus shipping
HP 6237B, +18vdc @ 1A, + 20 VDC @ .5A, -20VDC @ .5A, 110vac input, $50 plus shipping
HP 6289A, 0-40vdc, 1.5A, 110vac input $50 plus shipping
HP 230B RF power amplifier, 10mhz-500mhz, 110vac input $150 plus shipping
HP 334A Distortion Analyzer, 110vac input, $125.00, plus shipping
HP 3400A RMS voltmeter, 110vac input, $50 plus shipping
HP 11710B Down Converter, 110vac input, $100 plus shipping
Fluke 313A Voltage Calibrator, 0-50vcd, 0-2A, 110vac input, needs calibration, $75, plus shipping






[Non-text portions of this message have been removed]
HP items for sale

 

Hi,
I'm having trouble lifting heavy things now (surgery on both rotator cuffs), and the son will soon complete his Computer Engineering degree, move away, and then I'll try to move these and be scolded (again) by the surgeon.
Let me know if you want photos. All work, unless noted.

I realize the shipping costs for the heavy things make them less attractive, but trying here first.
Located in central Fla.听 Bring a chain saw.....

Thanks and 73
Frank Hughes
KJ4OLL

HP 6521A 0-1kv DC, 0-200ma, 110vac input $100 plus shipping
HP 6268B 0-40vdc, 0-30A, 240vac input $250 plus shipping
Harrison 6267A, 0-36vdc, 0-10A, 110 vac input, amp meter does not work. $50 plus shipping
Harrison 6367A听听0-36vdc, 0-10A, 110 vac input, $50 plus shipping
HP 6434B 0-40vdc, 0-25A, 110 vac input $150 plus shipping
HP 6237B, +18vdc @ 1A, + 20 VDC @ .5A, -20VDC @ .5A, 110vac input, $50 plus shipping
HP 6289A, 0-40vdc, 1.5A, 110vac input $50 plus shipping
HP 230B RF power amplifier, 10mhz-500mhz, 110vac input $150 plus shipping
HP 334A Distortion Analyzer, 110vac input, $125.00, plus shipping
HP 3400A RMS voltmeter, 110vac input, $50 plus shipping
HP 11710B Down Converter, 110vac input, $100 plus shipping
Fluke 313A Voltage Calibrator, 0-50vcd, 0-2A, 110vac input, needs calibration, $75, plus shipping

听
Re: 8568B YTO unlocked

 

I don't know about the screen flickering, but I do think the YTO loop behavior is normal. At wider spans it is not constantly phase-locked - it is driven open-loop with fairly accurate sweep current, and I think possibly re-phase-locked just at the beginning of the sweep each time around. For wide spans, you can't resolve the small frequency error on-screen anyway, but for narrow ones, more stability is needed, so the LO is locked. It's also possible that the narrow spans instead fix the first LO and use the second LO for sweeping - I can't recall for sure, but it should be one of those two schemes.

Definitely get the manual if you haven't already.

Ed
Re: HP 8341A sucessfully FIXED!

Adrian Nicol
 

Hi Tobias,
Great job and a great write-up to go with it, thanks for sharing your work.

Your story reminded me of something I learned from my first ever boss after I left school (over 50 years ago now - yikes!) he was an electronics engineer in the Radio Astronomy group at Cambridge and whenever we had to fix things that looked like they were 'no user serviceable parts inside' he would pick up a screwdriver, wrench or whatever and say "Well now, it didn't grow like that did it?" and would start taking it apart and more often than not he would fix it! I have followed that approach myself over the years and generally succeeded more often than failed too - and even when I fail I learn something!

Congratulations again on that fix!

Regards,
Adrian


On Sunday, October 15, 2017 2:30 PM, "Tobias Pluess tobias.pluess@... [hp_agilent_equipment]" wrote:


听
Hi all,
probably some of you have seen that I had some problems with a 8341A. It was indeed the YTO which failed! But, I was incredibly lucky to fix the YTO.
I also did a front panel RF output retrofit on my machine.
Some pics of the YTO and stuff can be found on my page, if someone is interested :-)



Now I can proceed to my next project, a 5342A frequency counter (hopefully not a blown sampler) and a 8568B spectrum analyzer with blurry focus on the graticule.

Best
Tobias, HB9FSX
Re: HP 60鈥檚 Front Panel Color

Adrian Nicol
 

Hi, I'm not sure there is an exact match in the RAL pallet. The nearest I have found for instruments of that vintage is RAL7042. That looks ok for panels that I wanted to 'tone in' with the HP equipment but it is probably not close enough to invisibly touch-up parts of an existing original panel. I have not explored it yet, but I gather there are now companies around who will colour (or color!) match from a sample and then mix an exact match for you. Some will do this in modest volume and for a reasonable cost, or so I am told!

Adrian


On Sunday, October 15, 2017 5:41 PM, "mmaseda@... [hp_agilent_equipment]" wrote:


听
Can some please share with me the paint code used by HP for front panels in the 60鈥檚? 听I have a very early 410C I鈥檓 trying to redo. 听The color is more dark than the RAL7044 used on the later 410C meters.
YTO coils in general..

 

开云体育

Hi guys. Over the years I have read a lot about yigs going bad specifically their coils seem to go bad. Is there anything that can be done pre-emptively to secure their longevity? And what exactly happens? Do the coils open due to excessive current (like a fuse?) I know there is an issue where the sphere sometimes moves and gets located incorrectly IIRC. I don鈥檛 know what causes that, perhaps excessive force? But I am interested in the coil issue. I have no yig issues at the moment, which seems like a good time to try to prevent it?

听

Eugene W2HX

听
Re: Restoring HP 1740A scope, strange waveforms seen, assistance please?

Bob Albert
 

I am not familiar with that model (I have a 1727A) but if it is anything close to the Tektronix 465, there are attenuator switches operated from the panel control that may be making poor contact.

I must get into my 465 to make such a repair.听 I have a spare 465B and hope that one has the parts I need.

Bob


On Sunday, October 15, 2017 6:05 AM, "dadhills@... [hp_agilent_equipment]" <hp_agilent_equipment@...> wrote:




The signal is being differentiated, as if it is being coupled through a small value capacitor.听 I would first look at the attenuator switch contacts on those particular v/div settings for an open or high resistance.听 In other words dirty switch contacts.

Dave

On 10/15/2017 7:51 AM, graham.l.n.butcher@... [hp_agilent_equipment] wrote:

Hi all, I've been a member for a while but lurking in the background while working on the scope and looking out for any discussions about a 1740A taking place.

I now have the scope in a running condition after replacing 2 faulty transistors and now while testing the scope with the 1V test connection I discover that channel B works as expected but channel A works OK up to 0.2V on the volts/div switch, moving to 0.5V and upwards the trace goes odd.听

I was wondering if anyone could point me to the area that I need to be looking at on channel A to cure the problem. I have uploaded photos of听 both channels with the settings on 0.5V and 1V so you can see the problem听

[url=][img][/img][/url][url=]B channel 1V dc[/url] by [url=]Graham Butcher[/url], on Flickr

[url=][img][/img][/url][url=]B channel 0.5V DC[/url] by [url=]Graham Butcher[/url], on Flickr

[url=][img][/img][/url][url=]A channel 1V DC[/url] by [url=]Graham Butcher[/url], on Flickr

[url=][img][/img][/url][url=]A channel 0.5V DC[/url] by [url=]Graham Butcher[/url], on Flickr

Thanks in advance for any help you can offer me.

Graham
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