I'm pretty sure I didn't have the scope set up optimally to be able to measure any ripple on the regulated outputs taken from the Test Points, but there didn't seem to be any sign of instability on any of them ("from a distance" as it were). The voltages were slightly out, though:
A8TP1 (+22V rail) read +23V
A17TP4 (+20V rail) read? +20V
A17TP4 (+12V rail) read? +12.275V
A17TP2 (+5.2V rail) read +5.175V
A18TP5 (-5.2V rail) read -5.16V
A18TP1 (-40V rail) read -39.6V
A18TP4 (-10V rail) read -9.88V
I'm no expert, but I can't see anything here which is far enough out of whack to cause the YTO unlock error. :-/
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Re: Mixing 'n' matching S parameter test sets
S parameters, as you know, can be characterized by S11, S21, S12 and S22. The two port test sets have enough directional couplers and power splitters inside to measure all four, by switching the direction of the RF feed, if directed to do all four measurements by the VNA controller. However, the 8754A was built long before that became a necessity for fast bench measurements. There are still just two ports on the test set, I am sorry if I confused the topic. I meant four S parameters being measured.
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Re: HP8903B - THD measure on Phono RIAA preamplifier
It is true that the freq response curve of RIAA standard deviates from flat, so that THD is not exactly what you think. However, RIAA preamps are typically measured that way. You could build a passive deemphasis network after the preamp to flatten it again and feed into the input of the test set. But you shouldn't be getting horrible THD numbers from a preamp in any case, and usually this indicates noise has crept in. A lot of work goes into microphone and phone cartridge preamps to reduce the noise from the IC's since they have high gain. Did you try filtering using 20KHz LPF for example? Does it have a powerline component to the noise, looking on the scope of the nulled output of the test set?
John Lyles
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Uploaded in files section all N28F010 dump of 54720A? FW ver. 4.07
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Oops, my mistake: the part-number for the MRC is 1820-2312, not 1820-2131.
The 1820-2131 is the microcontroller in the same counters, it is a mask-programmed Mostek MK3870.
Sorry for any confusion this may have caused !
Joel Setton
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Re: HP8903B - THD measure on Phono RIAA preamplifier
Attilio, What distortion values did you get? Also, what were the values you expected (and what is the preamp)? Is the level you are using for this testing appropriate for an RIAA preamp??
If indeed too far off, I'd recommend you look into possible sources of noise (such as improper?grounding), as the 8903 will return THD+N. For pure THD readings, I recommend you consider using an audio interface + something like ARTA. You can typically use the "monitor" output of the distortion analyzer to get a conveniently normalized level which would protect your interface and get the best of all worlds.?
Radu.?
Good morning everyone,
I recently bought an HP8903B audio analyzer, and I'm trying to test a RIAA phono preamp with it. I was able to check the RIAA response curve, but I didn't get decent results as far as the distortion measure is concerned.
I was thinking of inserting a precise reverse RIAA between the HP8093B output and the phono preamplifier input so that the HP8903B sees it as a line preamp and I can have a correct distortion measurement.
What do you think ?
Is there any better method?
Thanks for any advice / suggestion.
-- Cheers
??? Attilio
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Re: Looking for power supply schematic of Agilent 83751A
On 2/20/22 01:28, Lincheng Xiu via groups.io wrote: After 6 hours troubleshooting, it is fixed. The reason is C35 short. 100uF/50V electrolytic capacitor.
Here is what I traced the partial schematic of HP83751A power supply.
?After C35 short, the PWM controller does not drive the MOSFETs.
Also checked the ESR of C1, which is too much, 2 ohm, it will soon fail, just replaced with a new one. Wow, I see electrolytic capacitors like that dry out and lose capacitance all the time, but I don't think I've ever seen one shorted. Nice troubleshooting! -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Re: Looking for power supply schematic of Agilent 83751A
After 6 hours troubleshooting, it is fixed. The reason is C35 short. 100uF/50V electrolytic capacitor. Here is what I traced the partial schematic of HP83751A power supply.? ?After C35 short, the PWM controller does not drive the MOSFETs.? Also checked the ESR of C1, which is too much, 2 ohm, it will soon fail, just replaced with a new one. Regards Lin.
On Saturday, February 19, 2022, 03:03:07 PM EST, inlinebeginner via groups.io <inlinebeginner@...> wrote:
Hello
? Does anyone know where I can find the power supply schematic of Agilent 83751A or B (Synthesized Sweeper, 2 - 20 GHz) ?? I downloaded the service guide, it only contains block diagram (very helpful), but no detailed schematic. The power supply stopped working, I need to repair it.
? Symptom:? Could not power on. Rear panel 2 LEDs all off. Internal standby LED is on. Short A3W2 Pin 16 to ground, no response.
Thanks
Lin
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HP8903B - THD measure on Phono RIAA preamplifier
Good morning everyone,
I recently bought an HP8903B audio analyzer, and I'm trying to test a RIAA phono preamp with it. I was able to check the RIAA response curve, but I didn't get decent results as far as the distortion measure is concerned.
I was thinking of inserting a precise reverse RIAA between the HP8093B output and the phono preamplifier input so that the HP8903B sees it as a line preamp and I can have a correct distortion measurement.
What do you think ?
Is there any better method?
Thanks for any advice / suggestion.
-- Cheers
??? Attilio
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Thanks! I was having a devil of a job trying to find those test points! I never had such a problem with the old loose-leaf binder type manuals.
I'd expected to see *some* ripple present across the filter caps, but 10% was a surprise I must say.
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Typo correction: the 12V rail is at A17TP6 (not A17TP4).
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Re: Good Progress on 8753E EEPROM - Need More Guidance
Hi Marcus:
Yes, I am going to pull the second EEPROM Today, and read it. That one does have OPT6, so maybe I can correlate what address I need to focus on. Another member of the group sent me a .bin that seems to suggest F7 F7 F7 as opposed to 01 01 01 might have been the second issue I am having. I only chose 01, because the address where OPT11 resides had 01 to activate the option. Let me see what I can learn from the EEPROM which has OPT6 invoked.
Hopefully something I can make a better understanding of what is going on once I have the second EEPROM read.
Thanks,?
Rich?
On Sunday, February 20, 2022, 04:36:59 AM EST, Marcus Gustafsson <mankan@...> wrote:
Rich, the reason for not getting the results you expect is that you are assuming that 8753D and 8753E has the same EEPROM layout. I recommend using the 8753D EEPROM layout as inspiration only and that you focus on analyzing the differences in the two EEPROMs you have, to find what bits to flip. Best regards Marcus
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As Tom said, this is exactly as it should be!
You should not care much about ripple that you see before the outputs of the different regulators on the A8, A17 and A18 boards. However, you should see negligible ripple (less than 3mVp-p is typical) on the following test points:
A8TP1 (+22V rail)
A17TP4 (+20V rail)
A17TP4 (+12V rail)
A17TP2 (+5.2V rail)
A18TP5 (-5.2V rail)
A18TP1 (-40V rail)
A18TP4 (-10V rail)
When you test for ripple, stop the instrument from sweeping (e.g., by selecting "single sweep") as sweeping? introduces slight noise into some rails that is sometimes confused with ripple.
See the "Performance Tests and Adjustments Manual" section titled "Low-Voltage Power Supply Adjustments" subsection "RF Section" for the voltage tolerances for each supply rail and the locations of the different test points mentioned above (BTW, I could never find in the manuals a specification of the allowed ripples) .
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Re: HP-8753E R Channel Output Free Running
This one was solved this morning. It did not like the CAL data from the 8753E which this board has come from. I loaded the constants which came from the host machine and this seemed to resolve it.?
On Saturday, February 19, 2022, 11:34:35 PM EST, Rich Miller via groups.io <av8torrich@...> wrote:
Despite my initial success making progress on the EEPROM, it appears Murphy has struck. I started getting an error regarding the R Channel Input on my 8753E. When I plugged the R Channel output into my Spectrum Analyzer, I get the result as seen in the picture attached. Looks to me like something is free running at 2.55GHz or so.
I have the VNA in zero span at a frequency of 50MHz. As you will note the signal seems to be jumping all over based on my Max Hold capture. The primary signal is consistently at or around 2.5GHz (close to it), but makes massive excursions.??
I suppose not good deed goes unpunished! Time to start chasing this down.
Rich?
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Re: Mixing 'n' matching S parameter test sets
?I have to go against the the nay-sayers.
There is no reason why you cannot use the 85046A with the 8754A. The only issue is controlling it. Fortunatly the interface is really simple. You need 4 bits of data and a strobe (trigger) plus a 22V unregulated supply. Three of the bits are for the attenuator (10, 20, 40dB) and one for the RF relay / switch. So you need as a minimum 4 toggle switches and a push button switch plus DC power supply. If you want to get fancy a 3 bit Binary / BCD switch for the attenuator will allow direct selection.? You just set the switches and push the button.
A quick look at the manual and schematic should make it clear.
Robert G8RPI.
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A sawtooth ripple on the unregulated DC is exactly what you should
see -- the cap rapidly charges up when the rectifier forward biases,
but slowly discharges once the rectifier goes into reverse bias.
If the regulator always regulates, then that ripple is benign. That
is, ripple on the unregulated DC is to be expected. If ripple
doesn't show up on the output, then the regulator is doing its job.
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 2/20/2022 04:48, Jinxie wrote:
toggle quoted message
Show quoted text
Hi all,
This relates specifically to the 8566B but is no doubt relevant to
all analysers with linear power supplies.
My 8566B has been suffering from the infamous YTO ulock error and
it was suggested on some Youtube clip that it would be a good idea
to scope the power rails. To cut a long story short, I was seeing
ripple further down the line (in the direction away from the main
PSU section) so I decided to go back to the start and scope the
main storage electrolytics (you know, the big, beefy ones to use
the correct terminology). Anyway, they *all* have ripple on them
and it's more than I would expect, at around 10% of the DC
voltage. So for example on 12VDC I'm seeing just over a volt P-P
of ripple. Furthermore, it's not sine waveform either, but
saw-tooth! I did check these caps for ESR and capacitance some
time ago with my Peak ESR meter and they all came out OK as I
recall. So I'm not sure what to check next. Any suggestions? I've
got all the service manuals and whatnot on DVD but find it much
harder to follow what wiring goes to where without a proper
hard-copy book type manual to flick through. :(
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Hi all,
This relates specifically to the 8566B but is no doubt relevant to all analysers with linear power supplies.
My 8566B has been suffering from the infamous YTO ulock error and it was suggested on some Youtube clip that it would be a good idea to scope the power rails. To cut a long story short, I was seeing ripple further down the line (in the direction away from the main PSU section) so I decided to go back to the start and scope the main storage electrolytics (you know, the big, beefy ones to use the correct terminology). Anyway, they *all* have ripple on them and it's more than I would expect, at around 10% of the DC voltage. So for example on 12VDC I'm seeing just over a volt P-P of ripple. Furthermore, it's not sine waveform either, but saw-tooth! I did check these caps for ESR and capacitance some time ago with my Peak ESR meter and they all came out OK as I recall. So I'm not sure what to check next. Any suggestions? I've got all the service manuals and whatnot on DVD but find it much harder to follow what wiring goes to where without a proper hard-copy book type manual to flick through. :(
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Re: Mixing 'n' matching S parameter test sets
The antiquity of the 8754A is part of the appeal, though! It's closer to the fundamentals of network analysis and there are no abstraction levels between the operator and the machine as is the case with more modern kit. I should mention I'm heavily into vintage test equipment which has a certain appeal for my personally, though it wouldn't suit everyone of course.
I bought the 8754A and the storage normaliser for it many years ago but since I never had the S parameter test set for it, I never did much with it. More recently I acquired an 8753 series VNA together with the matching S parameter test set and it just occurred to me that I could fully check out the old VNA by hooking it up to the newer test set if that was possible without causing damage to either component. So there's a bit of background for you. Unfortunately from what's been posted to this thread it appears they just won't work together, however. :(
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The 1820-2131 is used in the 5315A/B and 5316A Universal Counters. I'm not aware if it being used in any other instrument.
Also known as the MRC, "Multiple Register Counter" and described with some detail in the January 1979 issue of HPJournal.
Pure unobtainum, I'm afraid ...
Joel Setton
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Re: Good Progress on 8753E EEPROM - Need More Guidance
Rich,
the reason for not getting the results you expect is that you are assuming that 8753D and 8753E has the same EEPROM layout.
I recommend using the 8753D EEPROM layout as inspiration only and that you focus on analyzing the differences in the two EEPROMs you have, to find what bits to flip.
Best regards
Marcus
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Jinxie
Dave McGuire
Attilio