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8116A Code 42
Mick B:
As my last post stated, something went wrong in the middle of calibrating this unit. I'm posting the results of my voltage readings after the failure. I had these ready to go but decided to check one last time so to be sure NONE of the readings were transposed (I'm dyslexic) and I will post those readings as soon as I can SOMETHING MORE is very wrong. Mark please what do you see here?
MarkL:
One thing that looks really strange is the -13.172V at the junction of R543, R544, R545, and R546. The other side of those resistors are at a much lower potential and they're all only 10 ohms, so either they're cooking or they're open if all those measurements in that area are right.
Can you double check that node? And on the other side of R547 since it's also at approx. -13.2V?
I'm not sure where the extreme negative voltage might be from, except maybe there's something wrong with CR513?
Mick B:
Hello all, while I was going to go over the voltages one last time, but after the error 51 showed up the voltages were so bad and so far off "negative voltages everywhere". it was just to ridiculous to post. I pulled Q512 and it testes good. put it back again, tweaked a few pots and NO error 51 its gone! :-//
I apologize for the erroneous voltages Mark noted, it was milli-volts at R547 & R545~R546
Please use these voltage Number 4.PDF file. Looking at TP4 & pins 18 & 19 of Q401 they test OK except the voltage on TP4 is low by about 1/2. Pg 10.4.12 fig. 10.4.7 on the 1v test, as the voltage goes up these stay the same. see Triangle.JPG.
I'm going to try to recalibrate up to the Shaper, just to see if I can get the basics going again, I don't know what happened, to cause error 51, but that needs to be found.
Mark as always, I will defer to you. Thanks
MarkL:
The voltage at TP4 should be a constant +/-0.5V peak when the output is set to 999mV, 10.0V 9.99V, or 16.0V. The voltage at TP4 is fed into a set of relay-controlled attenuators that set the final voltage going to the output amplifier. See the explanation on page 10.4-3 for more detail.
As for the readings at TP4 being low by 50%, first verify your scope is reading ok by looking at a fixed voltage. Measure something not in the 8116A that you know is right.
Check the reference voltage on the upper side of R411. It should be about 6.1V. The adjustment of R410 affects the amplitude, so it might be misadjusted. I don't know if it has the range to result in 50% like you're seeing, but it's something you're going to have check/adjust in the calibration procedure.
Your A1 board has seen a lot of issues and more are occurring every time you make some progress. You might want to consider buying a replacement A1, or even a scrap 8116A and take parts from it. There are also a lot of parts in common with the 8112A, so it would also be a good parts mule. You can probably get an 8116A for < $80; there's one for $50 being bid on right now with no errors showing. I guess it depends on your goal in pursuing the unit you have.
EDIT: Fixed voltage threshold; should be 9.99V.
Mick B:
I made it farther through the cal. this time, most of it. I skipped over some of the shaper adjustments mostly THD Harmonics I have a Siglent 1032X spectrum analyzer but at these low frequency's I am finding the FET in the Rigol MSO5354 to be most excellent. This is where I stopped tonight, at the beginning of Amplitude Modulation Pg. 918 so far so good. This cal. straightened out the strange triangle waveform. I'm thinking some of the shaper adjustments that call for readjusting all the pots that control the waveform balance NOT the balance between normal out, and COMPL. but pos and neg & amplitude that were already set maybe causing issues. This is my 3rd calibration attempt. so far so good.
I took your advice and bid on a $79 Working 8116A with option 001 and WON! It should be here before the end of the month.
Mark, this has been such a great learning experience, I just hope you stay on, I would like to tackle the smoking hot IC's and try out the HP 5005 Signature Analyzer at some point. This unit has had some issues, I just don't want to be defeated. These Function generators are spectacular, I would not like to end up in a landfill. I do not think we are here YET. :horse: After finishing up the basic cal. what next?
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