JingleDjango
Well-known member
I did. I couldn't get it that low. Gotta run but I'll post results later tonight. Thank you.
[BUILD] 1176LN Rev D DIY
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Echo North
Well-known member
JingleDjango said:
You may be just seeing oscillation then. Make sure your output is super neat and away from the PCB. Check all of the small blue caps values.
Mike
JingleDjango
Well-known member
I may have jumped the gun or been misinterpreting something yesterday evening because this morning I can get the output to 11dBu with the input at 0dBu as specified. However, turning R59 in either direction seems to have no effect on the output voltage per my DMM. Before installing the trim pots I confirmed that they were mid-sweep as suggested in the build guide (1k R for R59). Now I hesitate to over-turn them because I'm paranoid of breakage.
I'm now referring to this earlier part of the thread: http://groupdiy.com/index.php?topic=20058.msg623703#msg623703
With 1kHz @0dBu at the input:
Currently I get -9.7VDC on the leg of R35 directly next to R59, ~-2VDC on the farther leg.
R60 -2VDC on the leg closer to R35, 0.022VDC on the farther leg.
I pulled R59 to test it. I can sweep from 0 Ω-1.91Ω
I'm now referring to this earlier part of the thread: http://groupdiy.com/index.php?topic=20058.msg623703#msg623703
With 1kHz @0dBu at the input:
Currently I get -9.7VDC on the leg of R35 directly next to R59, ~-2VDC on the farther leg.
R60 -2VDC on the leg closer to R35, 0.022VDC on the farther leg.
I pulled R59 to test it. I can sweep from 0 Ω-1.91Ω
JingleDjango
Well-known member
I centered R59 again before reseating it.
I'm getting a very low VDC between CT and Q1's gate. -0.007VDC
Rotating R59 CCW by 5 half-turns lowers the voltage to -0.008VDC
Rotating R59 CW by 5 half-turns raises the voltage to -0.006VDC
My wiring looks right to me. The connections between each of the pads on the ratio board and the terminal blocks on the main PCB are continuous.
I'm getting a very low VDC between CT and Q1's gate. -0.007VDC
Rotating R59 CCW by 5 half-turns lowers the voltage to -0.008VDC
Rotating R59 CW by 5 half-turns raises the voltage to -0.006VDC
My wiring looks right to me. The connections between each of the pads on the ratio board and the terminal blocks on the main PCB are continuous.
Echo North
Well-known member
JingleDjango said:
0 Ω-1.91Ω or 0 Ω-1.91KΩ?
Echo North
Well-known member
What is your VDC at pad 18 when you rotate the QBias?
JingleDjango
Well-known member
Echo North
Well-known member
JingleDjango said:
Looks ok.
Now try same at pad 7.
JingleDjango
Well-known member
Very similar values. Around -2VDC to -1VDC. I think I can eek out a little more range but I'm being careful not to over-turn. Again, roughly 0.1VDC/full turn.
Echo North
Well-known member
JingleDjango said:
Seems about right. But nothing at the Q1 gate? What about the Q11 gate?
JingleDjango
Well-known member
q1 gate still reading -0.006VDC. Takes about 4 full turns of R59 to change that reading just 0.001VDC in either direction.
Q11 is lively. About -1.5VDC and responds more sensitively to the trim pot. I think this is in the right range, given the 'negative bias' explanation in the intro document? Perhaps a failed component?
Q11 is lively. About -1.5VDC and responds more sensitively to the trim pot. I think this is in the right range, given the 'negative bias' explanation in the intro document? Perhaps a failed component?
Echo North
Well-known member
JingleDjango said:
Can you safely remove Q1? If so does the voltage then appear at the gate pad?
JingleDjango
Well-known member
I have wick and a pump so I can give it a shot. I don't want to damage it.
Echo North
Well-known member
JingleDjango said:
Unless C22 is damaged I think it must be the FET.
JingleDjango
Well-known member
With q1 removed, at the q1's gate pad the reading now is -1.35VDC so that seems likely.
Echo North
Well-known member
JingleDjango said:
Send us an email. Let's get you new FETs.
Mike
JingleDjango
Well-known member
Thanks for helping with this!
Echo North
Well-known member
JingleDjango said:
Of course! Let us know if that fixes it.
Hello,
I'm writing this post because I'm having some issues with the 1176 rev D calibration. I'm at the third step of the calibration procedure( reduction meter tracking adjustment) and when I turn the R44 trim pot, nothing happens, the needle doesn't move. I've checked the R44 trim pot, but it is working properly. I've tried to redo the first steps of the calibration procedure, but the problem remains the same.
Can you help me ?
Thank you in advance,
Best regards,
I'm writing this post because I'm having some issues with the 1176 rev D calibration. I'm at the third step of the calibration procedure( reduction meter tracking adjustment) and when I turn the R44 trim pot, nothing happens, the needle doesn't move. I've checked the R44 trim pot, but it is working properly. I've tried to redo the first steps of the calibration procedure, but the problem remains the same.
Can you help me ?
Thank you in advance,
Best regards,
