Re: 5350/51/52 Sampler Replacement?
Thank you for your reply. I just went and made some quick measurements. J2 (LO out) is at +13.78dBm on my power meter, and the sweep from 292-355 MHz looks good on my spectrum analyzer.?
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With a 2GHz input, I can get a phase lock and accurate reading down to -22dBm. At 4GHz, I cannot get an accurate reading at all, even though the LED's are lit for phase lock. It's reading about 700 MHz low (3.313 GHz), even at +7 dBm from my signal generator.?
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If you look at the noise profile from the input port of my 5350B, it makes sense. The noise peaks around 4 GHz, and is about 20 dBm lower at 2 GHz. So with high enough input levels it is possible to overcome the noise. I would expect it to be the same at higher frequencies as the noise floor drops off again by 10 or so GHz, but the signal generator I was using only went to 4 gig so I didn't test that.?
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I had posted about this a few months back on the EEV Blog and it was suggested a diode in the U1 had likely shorted. This seems to make sense, given the amount of power present on the input connector. For reference, I also have a 5347A counter/power meter that uses the same sampler module, and when connected to the spectrum analyzer, the amount of "leakage" from the 50 ohm input is just over the noise floor, or about -50 dBm. I can get good sensitivity on that counter down to -40 dBm at all frequencies.?
?
?
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On Mon, Dec 9, 2024 at 03:58 PM, Yves Tardif wrote:
I made others measurements on my 8350B:
?
The signal output to the sampler, that is J2, and the signal has a variable frequency of 292-355MHz approximately (in theory: 295-350MHz), with a level of +14dBm.
No signal connected to input1.
To measure the LO output +14dBm at J2, I removed the loop from the module, and with a SMB to BNC adapter, I connected to my Spectrum.
?
I now put a signal at 1GHz, but at -40dBm, so that the meter does not synchronize.
So, you see the frequency values ??that the IF output of the sampler can take (theory: 500kHz-175MHz).
After this test, I put the 1GHz signal at 0 dBm, the meter synchronizes (phase-locked) and we can see one of the values ??that the IF output can take.
The meter is continuously measuring, so we can see the frequency excursion.
To do the closed loop measurement, I used a SMB test of my design, and the tap was -19dB, the insertion loss on the main line was -1.1dB.
By making several attempts, the IF outputs could be at another frequency, but the result displayed remains the same after processing.
?
In summary:
The LO measurement is +14dBm at J2 towards the sampler.
For a 1GHz -40dBm input, I get -37.45dBm at the IF output (not locked)
For a 1GHz 0dBm input, I get -1.14dBm at the IF output (locked).
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If you have the correct RF levels input-output to the sampler and the frequency range is similar, if the meter is not phase locked, then the problem is probably not in the sampler, but rather elsewhere like in the A5/A6 section for example.
?
Hope this information helps you.
?
Yves
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Re: HP 3325A amplitude problem
On Tue, Dec 10, 2024 at 12:55 AM, Raymond Domp Frank wrote:
The 3325A uses latching relays in its attenuator. These are mounted on the PCB and held with springs. The contacts between relays and PCB are prone to becoming dirty after many years. Remove the relay and clean the PCB and relay contacts with IPA. Do *not* use anything abrasive and be careful not to bend or even break a contact.
?
?
I guess I should clarify: The relays are an open construction: Their switching contacts employ the gold-plated PCB pads.
Once you see it, it'll become clear.
?
Raymond
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Re: 5350/51/52 Sampler Replacement?
Hi, ? First, I did the spurious comparison by measuring directly at input 1 of the 5350B, but I don't have an external 10dB attenuator. It's clear that you have much more spurious than my 8350B. ? 
? I made others measurements on my 8350B: ? The signal output to the sampler, that is J2, and the signal has a variable frequency of 292-355MHz approximately (in theory: 295-350MHz), with a level of +14dBm. No signal connected to input1. To measure the LO output +14dBm at J2, I removed the loop from the module, and with a SMB to BNC adapter, I connected to my Spectrum. ? I now put a signal at 1GHz, but at -40dBm, so that the meter does not synchronize. So, you see the frequency values ??that the IF output of the sampler can take (theory: 500kHz-175MHz). After this test, I put the 1GHz signal at 0 dBm, the meter synchronizes (phase-locked) and we can see one of the values ??that the IF output can take. The meter is continuously measuring, so we can see the frequency excursion. To do the closed loop measurement, I used a SMB test of my design, and the tap was -19dB, the insertion loss on the main line was -1.1dB. By making several attempts, the IF outputs could be at another frequency, but the result displayed remains the same after processing. ? In summary: The LO measurement is +14dBm at J2 towards the sampler. For a 1GHz -40dBm input, I get -37.45dBm at the IF output (not locked) For a 1GHz 0dBm input, I get -1.14dBm at the IF output (locked). ? If you have the correct RF levels input-output to the sampler and the frequency range is similar, if the meter is not phase locked, then the problem is probably not in the sampler, but rather elsewhere like in the A5/A6 section for example. ? Hope this information helps you. ? Yves
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Re: HP 3325A amplitude problem
The 3325A uses latching relays in its attenuator. These are mounted on the PCB and held with springs. The contacts between relays and PCB are prone to becoming dirty after many years. Remove the relay and clean the PCB and relay contacts with IPA. Do *not* use anything abrasive and be careful not to bend or even break a contact.
Let us know the result!
?
Raymond?
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HP 3325A amplitude problem
Just noticed that some of the amplitude levels are not correct on my HP 3325A that worked without problems for a long time. So before starting anything I wonder if anyone has experienced something similar: I setup sine signal in the 1 mV increments and from 1 mV rms to 10 mV rms levels are correct. Between 11 mV and 36 mV rms the levels can be few mV below or completely absent, haven't tested yet the other ranges. I'm doing measurements at 1kHz. Haven't tried other frequencies yet.
Some other observations - there is DC component present at the higher levels which I noticed earlier, ( at one occasion I setup sine signal at 2 V rms and I had 140 mV DC present while DC offset was set to zero)and DC offset is out of tolerance ( and we are talking about significantly out ( if I remember correctly manual allows 0.4 % of the set value for error of DC offset and I was getting error in the range of 4 % to 5 %.
Any input is appreciated.
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Thank you
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Re: HP 54720A comes on briefly then shuts off
Yes, it is the same supply!
toggle quoted message
Show quoted text
On Dec 9, 2024, at 15:51, Tim Tuck <timt@...> wrote:
?
Hi Yves,
Yes, my PSU is a 0950-2211
and I'd be interested in your experiments.
It'd be nice if we could come up with some
methodology to verify these things.
regards
Tim
On 9/12/24 15:47, Yves Tardif via
groups.io wrote:
Hi,
?
I don't have a
54720A, but an 83480A, similar to the 54750A. After checking
the 54720A service manual, it seems that the power supply is
the same.
My question is: is
the power supply of the 54720A really a Yokagawa PS495-0101,
the HP number is 0950-2211 for my 83480A.
?
If the number is the
same, I could try to run it outside (I have a spare power
supply to experiment).
But I know that if
there is no fan, or if it does not turn or stops turning,
then the power supply will go into shutdown mode...or
simply, will not turn on.
So, I have to find a
way to simulate the signal or connect a fan to it.
?
Without an electrical
diagram, it is quite difficult to repair this power supply,
but I succeeded three times on this model...and it was
painful...but feasible and inexpensive.
?
Yves
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Re: HP 54720A comes on briefly then shuts off
Hi Yves,
Yes, my PSU is a 0950-2211
and I'd be interested in your experiments.
It'd be nice if we could come up with some
methodology to verify these things.
regards
Tim
On 9/12/24 15:47, Yves Tardif via
groups.io wrote:
toggle quoted message
Show quoted text
Hi,
?
I don't have a
54720A, but an 83480A, similar to the 54750A. After checking
the 54720A service manual, it seems that the power supply is
the same.
My question is: is
the power supply of the 54720A really a Yokagawa PS495-0101,
the HP number is 0950-2211 for my 83480A.
?
If the number is the
same, I could try to run it outside (I have a spare power
supply to experiment).
But I know that if
there is no fan, or if it does not turn or stops turning,
then the power supply will go into shutdown mode...or
simply, will not turn on.
So, I have to find a
way to simulate the signal or connect a fan to it.
?
Without an electrical
diagram, it is quite difficult to repair this power supply,
but I succeeded three times on this model...and it was
painful...but feasible and inexpensive.
?
Yves
|
Re: Shielded probe cables?
OK. Not a fan of fine pitch :) But I will try to use the pods from my Agilent 54622D with the 32-ch analyser and see if it works. They have a straight 2,54mm pitch IDC connector.
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Re: HP 54720A comes on briefly then shuts off
Hi, ? I don't have a 54720A, but an 83480A, similar to the 54750A. After checking the 54720A service manual, it seems that the power supply is the same. My question is: is the power supply of the 54720A really a Yokagawa PS495-0101, the HP number is 0950-2211 for my 83480A. ? If the number is the same, I could try to run it outside (I have a spare power supply to experiment). But I know that if there is no fan, or if it does not turn or stops turning, then the power supply will go into shutdown mode...or simply, will not turn on. So, I have to find a way to simulate the signal or connect a fan to it. ? Without an electrical diagram, it is quite difficult to repair this power supply, but I succeeded three times on this model...and it was painful...but feasible and inexpensive. ? Yves ? 
? ?
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Show quoted text
-----Message d'origine-----
De?: [email protected] <[email protected]> De la part de Tim Tuck
Envoy¨¦?: 8 d¨¦cembre 2024 18:22
??: [email protected]
Objet?: [HP-Agilent-Keysight-equipment] HP 54720A comes on briefly then shuts off ? Hi all, ? My 54720A comes on briefly before switching itself off. ? No modules in frame. ? Been through section 5-12 of the service guide and I have all rail LEDs green and then LED1 on and LED2 off. ? Its not hot since its been off for a long time so I thought about the overload protection and did the resistance tests in fig 5-7 and all rails test as per instruction. ? Doing the instructions for the 5.1v and 120v rails pass as well. ? Before I proceed further with pulling cards, I thought I'd ask if there was a common fault or two I could go check for 1st. ? I'd also like to know if anyone has managed to power up the PSU outside the chassis for testing and what was the connectivity required to do that. ? If I can power up the PSU outside the frame I an eliminate that as a cause. ? thanks ? Tim ? ? ? ? ? ? ?
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Hi, Greg,
?
I'm Andrea, IW2FDH, from Italy,
?
Could you please post the? schematic of the HP 8980a/8981a power supply ?? Even without the removable vertical control board
?
thanks in advance
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Re: HP 54720A comes on briefly then shuts off
I have worked on many 54720, and the power supply is always the culprit of most issues. I was never able to find the schematic of that power supply!
toggle quoted message
Show quoted text
On Dec 8, 2024, at 17:22, Tim Tuck <timt@...> wrote:
?Hi all,
My 54720A comes on briefly before switching itself off.
No modules in frame.
Been through section 5-12 of the service guide and I have all rail LEDs green and then LED1 on and LED2 off.
Its not hot since its been off for a long time so I thought about the overload protection and did the resistance tests in fig 5-7 and all rails test as per instruction.
Doing the instructions for the 5.1v and 120v rails pass as well.
Before I proceed further with pulling cards, I thought I'd ask if there was a common fault or two I could go check for 1st.
I'd also like to know if anyone has managed to power up the PSU outside the chassis for testing and what was the connectivity required to do that.
If I can power up the PSU outside the frame I an eliminate that as a cause.
thanks
Tim
|
HP 54720A comes on briefly then shuts off
Hi all,
My 54720A comes on briefly before switching itself off.
No modules in frame.
Been through section 5-12 of the service guide and I have all rail LEDs green and then LED1 on and LED2 off.
Its not hot since its been off for a long time so I thought about the overload protection and did the resistance tests in fig 5-7 and all rails test as per instruction.
Doing the instructions for the 5.1v and 120v rails pass as well.
Before I proceed further with pulling cards, I thought I'd ask if there was a common fault or two I could go check for 1st.
I'd also like to know if anyone has managed to power up the PSU outside the chassis for testing and what was the connectivity required to do that.
If I can power up the PSU outside the frame I an eliminate that as a cause.
thanks
Tim
|
Re: 5350/51/52 Sampler Replacement?
Looks like plenty of strobe. Can you put a CW say a few GHz 0 dBm in the input, and tap into the IF signal from the IF amp output to show on the SA? If it's zero or very low compared to spec, then try to look at it near the input to the IF amp.
?
Ed
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Re: 5350/51/52 Sampler Replacement?
Hi Ed, thank you for your reply.?
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Regarding how I concluded the U1 was bad,? strong signals are making it through, as seen on my 8566B (pic below). This was with attenuation at -10dB and a 10dB pad in-line. SA was connected directly to the input on the 5350B. I have no idea on the history of this unit, or how that may have happened, as I received it this way.?
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I'm sure there are a lot of these floating around in the world and was hoping someone had cobbled together an acceptable replacement for the 5088-7071 from modern components. 20 GHz components are certainly more available now than they were 40 years ago!?
?
?
?
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Re: 5350/51/52 Sampler Replacement?
The first question is do you know how U1 got to be dead? A sure thing or suspicion?
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I'm pretty sure that part is a custom HP-made item, so there won't be a "modern" off-shelf substitute. Your best bet might be to find a maybe cheaper junker complete counter with a bad display or PS problem unrelated to the sampler. It's still a crap-shoot whether the front end is still good. I believe the U1 sampler is basically the same in all the models of this series, but differ in the type of coaxial connectors and cable going from the front panel into it, so it's conceivable that you may have more options to look for in junker units.
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A U1 setup from a junked higher-grade model could even provide a performance upgrade if you can figure out the details. I got one of these long ago for cheap. It had a burned out power transformer, and I managed to rig up a whole different kind of transformer and got it working with some design changes in the PS. When I studied the system in detail I found that the basic unit is the same for all models, and the particular one is set with various jumpers and such inside, As I recall, mine was originally a 20 GHz version, and I bumped it up to thinking it's the 26.5 GHz one. It worked more or less OK with the regular SMA interconnects, but to do it properly, it should have had the next step up in connector type. This is where the different grades of sampler come into play - a higher one can retrofit and probably work in a lower model instrument, and it can probably have even better performance attainable because it has the right interconnect.
?
Also, are you absolutely sure the U1 is bad? You can do various measurements around the sampler to get a better picture of what's going on inside. If you have the right kind of gear an easy first step is to look for strobe kickout signals from the microwave band input connector with a high speed scope or better, a spectrum analyzer. You should see fleeting sporadic impulse signals there as the counter runs through whatever its routines are to figure out what's there. If nothing shows down into the mV level, then something's wrong with the strobe, or possibly there's a blown bond wire in U1. If there are strobes, then try putting a valid CW microwave signal in and look for any IF signal all the way through the IF amplifier, and so on. Also check the strobes going into U1 from the driver amplifier. If those signals are all good but no IF, then the sampler diodes in U1 are probably shot. This can be a common failure since they're exposed to the outside world, but it's good to be sure.
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I don't know if the input is AC- or DC-coupled to the sampler. If DC, you may be able to see the diodes with a curve tracer on the input. It could show in various ways, like a termination resistance around 50 ohms, and maybe the diode conduction as voltage changes - it all depends on the topography. Use only low V and I for this sort of thing up to maybe a couple volts and few tens of mA - no more than the DC equivalent of the input RF power rating in 50R.
?
Also, does this have the input limiter option (opt 6 maybe)? If so, then U1 has a much higher amount of protection against normal abuse.
?
Ed
?
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5350/51/52 Sampler Replacement?
I have an HP 5350B with a dead A12 Microwave Module. It appears to be the "5088-7071" GaAs sampler (U1 in the block diagram). While there are a few A12 modules available, they're often more than an entire 5350B, and of course there's no guarantee of their condition.?
?
Has anyone been able to replace this component with a modern substitute? I cannot seem to find a datasheet that gives any details on the 5088-7071 that could potentially point me in the right direction.?
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Re: HP 8753A VNA - Help please: On the A9 (CPU) module where is the CC (NORMAL/ALTER) jumper?
Success!
After letting PRETUNE COR run for about five hours, I pressed Preset and stopped the cycle.
I had been sending source through 20 dB pad to R channel (no test set).
Replaced the 20 dB pad with an 8 dB pad in same path.
Re-did PRETUNE DEF (4 5) followed by PRETUNE COR (4 8); this time PRETUNE COR completed in a few seconds, ended with DONE, and after subsequent Preset it came back without start-up error message. Powercycling the unit had the same result.
I did this with both A9 CPU boards; the result was the same for both (and both now have their A9 CC jumpers back to normal position.)
Thanks for the getting-started advice, much appreciated!
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Re: HP 8753A VNA - Help please: On the A9 (CPU) module where is the CC (NORMAL/ALTER) jumper?
Update - have started the SOURCE PRETUNE CORRECTION CONSTANTS procedure.
There are two steps -
First is "PRETUNE DEF" (test 45); this completed successfully (the manual says it would display "CORRECTION CONSTANTS NOT STORED" if the EEPROM were not written, so that's a good sign. That test ran instantly.
Second is "PRETUNE COR" (test 48). This has been running now for about half an hour. The signs of activity are
1. The test status says -IP- (probably "in process" or something to that effect)
2. A small arrow on the CRT to the left of the grid (at about line 6 from the bottom) is coming on and off at a 1 Hz rate
3. A vertical line, just to the right of the left axis of the grid, is varying in height (from the bottom) between about 2 divisions, and occasionally going all the way to full scale height. It appears to update about once a second.
I will need to leave it running at this point but will check on it from time to time. Hopefully it finishes by tonight!
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Re: HP 8753A VNA - Help please: On the A9 (CPU) module where is the CC (NORMAL/ALTER) jumper?
Hi Chuck,
I think I have enough information to proceed --- I went back to the schematic of the A9 board, and the jumper pins E25 and E26 enable a write signal to go to the EEPROM, which is a 24-pin device that may be a 2816 type (the part on the CPU board here is an Intel D2817; found a datasheet for that online, so that means I should be able source replacement EEPROM(s), as the EEPROM back-up/restore facility in the 8753 depends on the 9122 series floppy drive (don't know if this can be done with HPIB interface, haven't checked.)
E25 and E26 are on the top pair of pins on my boards (both); they may be on the far right pair of pins on your board(s) where the header is horizontally oriented. Given that, I'm OK to proceed attempting to access EEPROM from the test/diagnostic menus in the 8753A. If there's a diagram of the board layout(s) anywhere in the documentation I've found online so far, I've overlooked the needed resource. Fortunately the boards are pretty well marked as to what major part is where.
Your two CPU boards are possibly from 8753B or 8753C; the 8753A never had option 006 (6 GHz) nor 002 (Harmonic mode), only option 010 (Time Domain. )
So, I think at this point I can proceed with attempting recovery of the 8753A with it's replacement CPU board.
Also, the other 00067 board I have here might be from the HP 8702A (lightwave analyzer, pretty much some early part of the 8753 family), but not sure. Anyway, gotta burn only one bridge at a time!
Thanks again for your time and exploration of your lab equipment on my behalf!
I'll report back (here) on whatever success/failure I encounter.
Dave
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Re: HP 8753A VNA - Help please: On the A9 (CPU) module where is the CC (NORMAL/ALTER) jumper?
Dave,
I got to both units.
The working one is #2828A04434, OPT 002 & 006
CPU board is 60079, Revision 3.0 Firmware.
The header is horizontal to the left of U36, marked from left E25,
E27, E29, E31, blank. The run jumper is on the E25 pins
The bad CPU unit is #2807A04011, OPT 002, 006, 010
CPU board is 60129, Revision 2.01 Firmware
The header is also horizontal the same as above
As far as getting the board out without the lift tabs, I use a pair
of vise grips at the center of the board edge where the pin header
is located, doesn't take a lot of force to pull it up.
Hope this helps your problem.
Chuck
On 12/7/2024 1:31 PM, ChuckA wrote:
Dave,
The 60009 board is he one the manual says there is no docs for but
it's similar to the 60079
board.
?
I'll open the working one this afternoon, I think there's another
one with a bad CPU board in my storage shed that I just haven't
wanted to spend time on, I'll look for that one too.
Chuck
On 12/7/2024 12:59 PM, David Feldman
via groups.io wrote:
Thanks, Chuck - I really appreciate your time/interest in helping with this!
The A9 board number ends in 60009. I've got another A9 board (however, it's removal latches are missing and it's "distressed" at those corners due to some abuse in it's history) which ends in 60079. Both have a 5-jumper array in the lower left corner. Both are equipped with same version of EPROM 1.01 (6 parts, specific part numbers but sharing the same revision marking.)
Both A9 boards (I didn't include this info with original posting as it didn't seem relevant, but given the existence of A9 board versions for 8753A and your notes above) appear operational as far as I can tell (and in terms of the self-test diagnostic for internal tests which passes in both cases), but existence of incompatible EEPROM constants (that applied to whatever machine these previously lived in, long ago) is causing what appears to be pretune failure. I'm focusing on the 60009 board currently (as changing the CC jumper requires removal of the board and removal without the eject parts is doable but tedious).
So, if you are able inspect the A9 board in your 8753A and suggest which is the CC position, that should apply to both boards here (i.e., is the "CC" position at the top of the 5x2 header, or other position; the normal operating jumper position appears to be at the bottom of the header pin group from your initial response and by inspecting both boards here.)
As an aside, I read through the section in the PDF service manual on adjustments/calibration constants; it appears the pre-tune issue has a specific diagnostic step which can regenerate the parameters and those get rewritten to an EEPROM somewhere on the CPU board, and from seeing a few other posts on the issue (need follow a procedure after A9 module replacement) this is a common situation (such as these things would go nowadays!)
So, again I appreciate your willingness to pitch in and advise!
Dave WB0GAZ
--
See Early TV and Vintage Test
Equipment
Chuck Azzalina
--
See Early TV and Vintage Test
Equipment
Chuck Azzalina
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Anders