[BUILD] 1176LN Rev D DIY

[usekgb]

it's always nice to have some lights...i ran my led's the same but no cap or diode?

I couldn't find any documentation about the power requirements for the LED's in the meters, so I decided to play it safe and send them DC.  Better to be safe than burn out the lights. 

Cheers,
Zach

 

[HMPS]

Hello fellow builders.

The BOM only shows three 2k variable trimmer potentiometer's but on the board there are 4 slots for them

My R44 is empty.

Do I need to order another 2k variable resistor and put it in there?

Thanks folks.

HMPS

 

[number2]

Hello fellow builders.

The BOM only shows three 2k variable trimmer potentiometer's but on the board there are 4 slots for them

My R44 is empty.

Do I need to order another 2k variable resistor and put it in there?

Thanks folks.

HMPS

I don't have one at R44 and I'm almost done. You need theose at R59, R79 and R86. I believe. and R71 is your big zero set pot

here's my question: I have completed steps 1 and 2 of the calibration. I get nothing but blown fuses for step 3.
I try to send a .775 VAC, 1kHz tone and I am getting no response whatsoever. little help please. 

 

[Biasrocks]

I basically turned the input and output up 100% and just recorded the noise back into the DAW. 

Hey Dan,

Looks like oscillations of some sort, try re-routing the internal audio wiring and checking your grounds.

I just checked mine (mono build) and the only thing I'm seeing with the in/out cranked is residual ground hum at around -50dbv. There is no change if the input is full or off.

Regards,
Mark

 

[dandeurloo]

ok, thanks.  I think I may just try re wiring it all. 

 

[dmp]

Check that the audio ground is connected to the chassis at one place. I had a rev A build that oscillated for this reason.
These boards have a ground plane which can be problematic if not connected properly, I believe

 

[number2]

I am itching to finish.  :'(I got steps 1 and 2 done of the calibration.

I get no response whatsoever on step 3 and I keep blowing fuses.

checking voltages: Q13 seemed off. I read -.9,-1.4 and -1.5 at Q13. None of those readings were close to 9.75 VDC which was supposed to be the value going to R74, correct?

Oh the middle pin of Q13 charges (probably up to 9.8 vdc)

I did check R74 though and I got 9.8 vdc on one side and -1.5 vdc on the other. that's not right, right?

For Q6 I measure 2vdc at C13 and 27.1 vdc at R33. Is that how I check Q6?

everything else is close to correct values except at R17 I get 25.2 vdc in stead of 30vdc.

Does this explain not passing audio and/or blowing fuses?

advanced thanks

 

[number2]

i am passing audio but my meter stays at -20 no matter what i do with input or output knobs for step 3 in calibration.

i made the signal tracer by mark burnley but i don't know where to put it besides the in/out XLR's

also when i touch my chassis i begin to hear signal passing.

 

[dmp]

here's my question: I have completed steps 1 and 2 of the calibration. I get nothing but blown fuses for step 3.
I try to send a .775 VAC, 1kHz tone and I am getting no response whatsoever. little help please. 

You aren't passing audio and you're blowing fuses, but you have completed steps 1&2 of the calibration?

Take a step back.
Pull out the FET, which causes gain reduction.
Your unit should pass audio. If not, there is a problem in the input amp or the output amp. If you are blowing fuses, I would guess you have a problem in the output amp.
So do some tests.
Hook up a signal to the input, use the signal tracer to see if the signal is present at the input to the pcb (output of the transformer). 
If it is, use the signal tracer to see if the signal is present at the input to the output volume pot.
If it is, then the problem is in the output amp.
Check the voltages on the components in the output amp. Check that the components are right. Post more info if you need help. Pictures of your build. Post the schematic with your voltages (listing all the voltages in text may be easier for YOU, but not for the person you are asking to help you).

checking voltages: Q13 seemed off.

Don't worry about the meter driver yet - get the signal preamp and output amp working first.

 

[number2]

Hook up a signal to the input, use the signal tracer to see if the signal is present at the input to the pcb (output of the transformer). 
If it is, use the signal tracer to see if the signal is present at the input to the output volume pot.
If it is, then the problem is in the output amp.
Check the voltages on the components in the output amp. Check that the components are right. Post more info if you need help. Pictures of your build. Post the schematic with your voltages (listing all the voltages in text may be easier for YOU, but not for the person you are asking to help you).

checking voltages: Q13 seemed off.

Don't worry about the meter driver yet - get the signal preamp and output amp working first.

thanks so much dmp!
i signal traced and i have signal passing at all of the pots, input/output XLR's, output transfrmr and at input to pcb.

voltages:
signal preamp:
Q2: 1.05, 1.7 and 0.5
Q3: 1.75, 11.76 and 1.15  (11.76 should be closer to 12.5?)
Q14: 11.76, 29.6, 11.17

signal line amp: (is this the output amp?)
Q4: 0.98, 3.9 , 0.42
Q5: 3.2, 24.3, 2.6
Q6: 27.1, 2, 2      (this 27.1 should be closer to 28.9?)

GR control amp:
Q7: 14.82, 4.37, 3.8
Q9: 16.3, 3.38, 2.8

 

[dmp]

Are these problems fixed?

also when i touch my chassis i begin to hear signal passing.

I keep blowing fuses.

not passing audio

If your unit is passing audio correctly and the pots work to adjust the levels... then you can move on to calibrating the unit.

 

[rokus666]

Hello all,

I have just started my first 1176 build.

I have started with wiring power supply and power transformer.

I have measured the power rail voltages:

-9.74 VDC
+29.78

is this okay?

The grounding on the case is fine.

After I measured the voltages, I unplugged AC cord from the wall.
Is it safe to touch the PCB? Are the capacitors charged with some dangerous voltages?
How would I know I am safe to proceed stuffing the board with everything else?

 

[Echo North]

Hello all,

I have just started my first 1176 build.

I have started with wiring power supply and power transformer.

I have measured the power rail voltages:

-9.74 VDC
+29.78

is this okay?

The grounding on the case is fine.

After I measured the voltages, I unplugged AC cord from the wall.
Is it safe to touch the PCB? Are the capacitors charged with some dangerous voltages?
How would I know I am safe to proceed stuffing the board with everything else?

Those voltages look great.

I've never discharged the PS caps, but it's not a bad idea.  You could use some insulated clips and connect the cap leads through a resistor.  A 200Ω 5W resistor would probably work fine.

 

[number2]

Are these problems fixed?

also when i touch my chassis i begin to hear signal passing.

I keep blowing fuses.

not passing audio

If your unit is passing audio correctly and the pots work to adjust the levels... then you can move on to calibrating the unit.

I incorrectly stated that I wasn't passing audio. I have steps 1 and 2 done of the calibration but my meter does not move at all for step 3.

I don't know what to do about the chassis and I haven't blown a fuse today or yesterday.

 

[rokus666]

Thanks for the reply. I am building my first mono compressor, but planning to add another one for stereo operation.

I want to make something clear before I start building:

Is it possible to stereo link two Mono 2RU compressors with the stereo link kit?

If that's the case, should I just put in 2x2 matched FETs in both compressors?

 

[Echo North]

Thanks for the reply. I am building my first mono compressor, but planning to add another one for stereo operation.

I want to make something clear before I start building:

Is it possible to stereo link two Mono 2RU compressors with the stereo link kit?

If that's the case, should I just put in 2x2 matched FETs in both compressors?

Yes you can link 2 mono units with the link kit.  The process is described in the doc on the link product page.  The FETs just need to be reasonably matched.  If you order 2 sets of FETs on my shop they will be in the same ballpark.

 

[dmp]

I don't know what to do about the chassis

Probably a grounding problem. You can search and read about best practices for grounding audio gear.

Seems you are down to a problem with the metering circuit.
These measurements seem funny:

checking voltages: Q13 seemed off. I read -.9,-1.4 and -1.5 at Q13. None of those readings were close to 9.75 VDC which was supposed to be the value going to R74, correct?
Oh the middle pin of Q13 charges (probably up to 9.8 vdc)
I did check R74 though and I got 9.8 vdc on one side and -1.5 vdc on the other. that's not right, right?

R74 should be seeing 0V on one leg, and -10v through the resistors off the other leg. I don't see how it could be positive.
Take a few minutes to try to understand the schematic. Learn ohm's law and see how the voltages are interrelated.

 

[rokus666]

Yes you can link 2 mono units with the link kit.  The process is described in the doc on the link product page.  The FETs just need to be reasonably matched.  If you order 2 sets of FETs on my shop they will be in the same ballpark.

I have actually ordered the complete kit from your shop. Will do the same for my next build.
What would be the best FET option when planning for the next build and using two units linked ? Should I buy 2x2 FET from you now, or all FET's that come from your shop are reasonably matched? A bit confused.

I still haven't soldered the FET's to the PCB just because of this reason.

I just want to be sure that my next build will work with this one I am working on right now.

 

[dmp]

I went to great lengths to build a matched pair of 1176s. I did the matching myself and went through a lot of FETs in order have a matched quad.
Even with the nice stereo link boards, the FETs all need to be matched I think

 

[Echo North]

Yes you can link 2 mono units with the link kit.  The process is described in the doc on the link product page.  The FETs just need to be reasonably matched.  If you order 2 sets of FETs on my shop they will be in the same ballpark.

I have actually ordered the complete kit from your shop. Will do the same for my next build.
What would be the best FET option when planning for the next build and using two units linked ? Should I buy 2x2 FET from you now, or all FET's that come from your shop are reasonably matched? A bit confused.

I still haven't soldered the FET's to the PCB just because of this reason.

I just want to be sure that my next build will work with this one I am working on right now.

Basically I match say 60 pairs according to their characteristic curves then sort them from "low" to "high" (of that makes sense).  So a matched pair is very close in curve to the ones on either side of it in the stack.  Any time you order FETs or multiple kits, I grab from the stack and you'll get FETs that are very close in matching.

If you order sets at different times, they can be from anywhere in the stack and may not match enough for linking.

If you've previously ordered a kit and are now ordering another, just order the kit and note in the order comments that this is your second kit and you want to link it to another.  I'll throw in the second set for free.

Mike