[BUILD] 1176LN Rev D DIY

[JingleDjango]

I did. I couldn't get it that low. Gotta run but I'll post results later tonight. Thank you.

 

[Echo North]

I did. I couldn't get it that low. Gotta run but I'll post results later tonight. Thank you.

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

 

[mgalimbe]

I forgot to mention that I have .278vav at the input pad on the  main pcb

Check all of your components in the box labeled "Signal Preamp".  Make sure you have the R values right, like you don't have a 56K or 560K mixed up.  Check everything super close.

Check the DC V in that section against these values:
http://mnats.net/files/1176REVD_VOLTS.pdf

Mike

Mike

hi mike

I'm still checking but I did find one resistor R7 it should be 2.2m but I have a 226k there so Ill replace that and see. I'll post up once I fix that and finish checking the rest of the resistors.

 

[JingleDjango]

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

 

[JingleDjango]

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.

 

[Echo North]

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

0 Ω-1.91Ω or 0 Ω-1.91KΩ?

 

[Echo North]

What is your VDC at pad 18 when you rotate the QBias?

 

[JingleDjango]

Sorry, I did mean KΩ.

At pad 18, I first read -1.9VDC. This is with the trim pot roughly centered. I get about 0.1VDC shift per full rotation of the dial.

 

[Echo North]

Sorry, I did mean KΩ.

At pad 18, I first read -1.9VDC. This is with the trim pot roughly centered. I get about 0.1VDC shift per full rotation of the dial.

Looks ok.

Now try same at pad 7.

 

[JingleDjango]

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]

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.

Seems about right.  But nothing at the Q1 gate?  What about the Q11 gate?

 

[JingleDjango]

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?

 

[Echo North]

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?

Can you safely remove Q1? If so does the voltage then appear at the gate pad?

 

[JingleDjango]

I have wick and a pump so I can give it a shot. I don't want to damage it.

 

[Echo North]

I have wick and a pump do I can give it a shot. I don't want to damage it.

Unless C22 is damaged I think it must be the FET.

 

[JingleDjango]

With q1 removed, at the q1's gate pad the reading now is -1.35VDC so that seems likely.

 

[Echo North]

With q1 removed, at the q1's gate pad the reading now is -1.35VDC so that seems likely.

Send us an email. Let's get you new FETs.

Mike

 

[JingleDjango]

Thanks for helping with this!

 

[Echo North]

Thanks for helping with this!

Of course!  Let us know if that fixes it.

 

[Ataraxia]

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,