[BUILD] 1176LN Rev D DIY

[Echo North]

Do this:
http://groupdiy.com/index.php?topic=20058.msg769979#msg769979

Start with a 1K signal and note the voltages. Then do the same with 100hZ signal. Voltages should be the same, see where they start not being the same.

Mike

 

[JingleDjango]

Wow, I can build a freaking compressor but I can't wire a cable correctly. Just to give a heads up to anybody else who may encounter a compressor or piece of hardware that completely sucks the bass out (e.g. low cut/high pass filter/unintentional asshole), the problem was my input cable. I was running the compressor into my patch bay using an XLR to 1/4" TRS cable that was wired incorrectly causing phase problems. The compressor seems to be working correctly. I'm going to try calibrating it tomorrow and make sure that everything else is functioning correctly before I get my hopes way to high, but for now it sounds great!

Thanks for the quick response, Mike. Thankfully I caught this post before I opened things up and started poking around needlessly. I had a strained cable with a bad connection. I put a new connector on and now everything is fine again. So glad I checked the cable!

Phew.

 

[Echo North]

"Try:
http://groupdiy.com/index.php?topic=20058.msg769979#msg769979"

thx, I saw that post but since I couldn't get the .775 to even show correctly on the input xlr (across 2/3 it's around .3) I figured it wouldn't be of much help. anyhoo, here's my readings VAC testing to ground with a .775 vac 1khz signal sent into it.

1. T-Pad input =  .155
2. T-Pad output =  .095
3. Input transformer primary = .095
4. Input transformer secondary = .03
5. At the Input + terminal at the main PCB = .03
6. C7 + pad = .645
7. C7- pad = .645
8. Blue wire on output transformer = .07

hope that helps diagnose the problem, or at least point in the right direction

That was with GR OFF and the input mid-way?

 

[junkface]

That was with GR OFF and the input mid-way?

ya. GR off and input at 12 o clock (24). Double checked the 1k signal I was sending and was getting .775 exactly, but as soon as I test the xlr input it's down to around .3 , with the aforementioned VACs  following from there down the signal path . I'll try the  100hz signal and see what happens there. thx for the help!

 

[junkface]

"Try:
http://groupdiy.com/index.php?topic=20058.msg769979#msg769979"

thx, I saw that post but since I couldn't get the .775 to even show correctly on the input xlr (across 2/3 it's around .3) I figured it wouldn't be of much help. anyhoo, here's my readings VAC testing to ground with a .775 vac 1khz signal sent into it.

1. T-Pad input =  .155
2. T-Pad output =  .095
3. Input transformer primary = .095
4. Input transformer secondary = .03
5. At the Input + terminal at the main PCB = .03
6. C7 + pad = .645
7. C7- pad = .645
8. Blue wire on output transformer = .07

hope that helps diagnose the problem, or at least point in the right direction

100 hz doesn't change anything really. still drops to about .3 vac soon as it hits the input xlr. from there it's looking the same.
1. T-Pad input =  .155
2. T-Pad output =  .095
3. Input transformer primary = .095
4. Input transformer secondary = .03
5. At the Input + terminal at the main PCB = .03
6. C7 + pad = .643
7. C7- pad = .643
8. Blue wire on output transformer = .07

I think I just figured out that it's the T-pad (or it's little PCB?) that is messed up, though. I was just trying to see what I'd need to remove to see the proper level 1khz signal across pins 2/3. Started by disconnecting the pcb, still got the drop.  Then I removed the input xfo, and still got the drop. Once I removed the T-pad I was finally able to read the .775 vac across pins 2 and 3. The soldering is clean as a whistle on the T-pad, so I doubt there was any issue there. Should I reseat that in it's PCB just to be safe though? I could wire it without the little pcb to make sure that that's not the problem, or is the bournes pad is just a dud? Not sure what the next step is exactly.

 

[junkface]

well shoot.  tested the attenuator and it seems to be functioning correctly, or at least it's giving the proper resistance of 0-1k+.  is there some other aspect of it other than resistance that could be gumming up the works? suppose I'll go through and redo the input wiring one more time. other than that (or the Tpad pcb) I can't think what could possibly be the problem.  ???

 

[Echo North]

Both the T-pad and the input transformer are designed to drop voltage/signal.

What happens if you put you DMM across pin 2 and 3 of the input xlr, and adjust your signal source so you see 0.775 VAC across pin 2 and 3. You may end up having your signal source be 2+ VAC to get 0.775VAC due to impedance.

Mike

 

[junkface]

interesting i don't recall ever having to crank the test signal so crazy high to get 0db on the input. in any event I rewired it again JIC, still was getting the 1/2+ voltage drop, but I just cranked my test signal like you recommended and  it seems to be calibrating up fine now. It does seem to be quieter than the other Rev D i have in my studio, (I'll have to do some A/B testing to confirm or disprove that) but it sounds good, the meter is tracking correctly and all.
thanks for the help mike!

 

[Echo North]

interesting i don't recall ever having to crank the test signal so crazy high to get 0db on the input. in any event I rewired it again JIC, still was getting the 1/2+ voltage drop, but I just cranked my test signal like you recommended and  it seems to be calibrating up fine now. It does seem to be quieter than the other Rev D i have in my studio, (I'll have to do some A/B testing to confirm or disprove that) but it sounds good, the meter is tracking correctly and all.
thanks for the help mike!

If you put it in GR OFF mode, feed it a -40dB signal, and max the in/out, you should see 42-45dB of gain.  Needs to be a signal below -20dBish or you'll just hit the max output.

Measure at the input (2 and 3) and output (2 and 3) to get your levels.

http://www.sowter.co.uk/decibels.php

Mike

 

[MPCNYC]

Built 2 REV D comps awhile back. One works fairly flawlessly. The other exhibits a strange behavior, that's sort of getting worse as
times been passing. When I turn the unit on Ratio is at 4, Meter is at GR. The VU needle doesn't  move to the right. And either no sound or a thin sort of distorted sound occurs when passing signal.Usually,  If I "tap" the VU meter repeatedly for a few moments, the meter will then go to the left and the compressor will sound normal. Any thought on how to remedy this??

TIA

 

[Echo North]

Built 2 REV D comps awhile back. One works fairly flawlessly. The other exhibits a strange behavior, that's sort of getting worse as
times been passing. When I turn the unit on Ratio is at 4, Meter is at GR. The VU needle doesn't  move to the right. And either no sound or a thin sort of distorted sound occurs when passing signal.Usually,  If I "tap" the VU meter repeatedly for a few moments, the meter will then go to the left and the compressor will sound normal. Any thought on how to remedy this??

TIA

Something loose.  Not in the meter though. Loose connections in the meter would not change the sound...unless there was an internal short I suppose.  Is it only with the 4 ratio?

Maybe disconnect the meter signal terminals, use for a bit,  and see if that fixes the sound. If it does than it's the meter.

Mike

 

[mgalimbe]

I just looked online they have 500mA is that too much?

It's not ideal, but you certainly won't blow it.


However if there is an issue with your build it might not blow to prevent on PCB damage. I'd use it in a pinch, but it's your call.

Mike

Well theres definitely an issue with my build.  :'(The only other size they have in stock is 315ma which might be too small. I'll just order some from mouser. unless you think the 315 will work for now.

You could try it. Personal I would just use the 500mA.  Any major issue is going to blow 500mA.

Whereas this is my first build and I really don't know what is wrong with my build I'd rather get the right fuse so that we can figure out whats going on without complicating things. I just ordered a bunch, so I will post up once they arrive in a few days.

ok just got my fuses in. I think I may have found the problem with my initial post (months ago) about not making it through the first calibration step. What I noticed is that the light for the meter is on when the switch is in the off, +4, +8 position but the light goes off in the GR position. Would this be why I'm not seeing the voltage when I apply the test tone for the calibration test? it seems like the GR switch position is off and the off position might be the GR setting.

 

[Echo North]

I just looked online they have 500mA is that too much?

It's not ideal, but you certainly won't blow it.


However if there is an issue with your build it might not blow to prevent on PCB damage. I'd use it in a pinch, but it's your call.

Mike

Well theres definitely an issue with my build.  :'(The only other size they have in stock is 315ma which might be too small. I'll just order some from mouser. unless you think the 315 will work for now.

You could try it. Personal I would just use the 500mA.  Any major issue is going to blow 500mA.

Whereas this is my first build and I really don't know what is wrong with my build I'd rather get the right fuse so that we can figure out whats going on without complicating things. I just ordered a bunch, so I will post up once they arrive in a few days.

ok just got my fuses in. I think I may have found the problem with my initial post (months ago) about not making it through the first calibration step. What I noticed is that the light for the meter is on when the switch is in the off, +4, +8 position but the light goes off in the GR position. Would this be why I'm not seeing the voltage when I apply the test tone for the calibration test? it seems like the GR switch position is off and the off position might be the GR setting.

That's interesting.

Do you have a picture of your meter switch?

 

[mgalimbe]

mike,

I'm an idiot after studying the image I had the switch upside down. so it is wired correctly. just to verify though when doing the initial calibration step if the switch was in the off position I wouldn't get a reading on the output xlr correct?

 

[Echo North]

mike,

I'm an idiot after studying the image I had the switch upside down. so it is wired correctly. just to verify though when doing the initial calibration step if the switch was in the off position I wouldn't get a reading on the output xlr correct?

Right the unit is OFF. So no signal.

 

[mgalimbe]

mike,

I'm an idiot after studying the image I had the switch upside down. so it is wired correctly. just to verify though when doing the initial calibration step if the switch was in the off position I wouldn't get a reading on the output xlr correct?

Right the unit is OFF. So no signal.

Thanks, Hopefully this was the reason. I will start the calibration process and post up once I'm done. Thanks for your help.

 

[mgalimbe]

ok so after getting the right fuses, I went back to the beginning and heres what I got. It seems that the problem is with the input transformer.





From Mike at hairball:
Easiest way to check for signal is to use a DMM set to read AC volts.

Turn the attack pot to the GR off position. Set your input and output to mid rotation and your release fully CW.  Feed the unit a 1kHz, 0dB signal (0.775VAC).  Confirm you have 0.775VAC between input pins 2 and 3.  Now follow the signal using ground and you common reference point (where you put the black lead).  You can attach it to ground at the 0V/CT terminal at the PCB power supply.

Measure the VAC against ground at:

1. T-Pad input + (should be about half of 0.775)
2. T-Pad output +  (should be even smaller)
3. Input transformer primary + (should be the same as step 2)
4. Input transformer secondary + (getting smaller)
5. At the Input + terminal at the main PCB (should be roughly 0.06 to 0.09VAC)
6. C7 + pad (should be much larger now, around 2.0 VAC)
7. C7- pad (should be the same as  #6)
8. Blue wire on output transformer (should be a large VAC number)

Report back. That will help determine where the signal is dying.

Mike
[/quote]

Here are my findings:

input xlr=.776vac
Tpad in+=.392
Tpad out+=130.5
Input trans. Pri +=130.2
Input Trans 2nd+= 145.7 (here is where I see the problem, this number is getting larger instead of smaller)
Input + terminal of main PCB=.1v
I have nothing on either pin(+or-) of c7.
blue wire on output transformer=00.00
[/quote]
[/quote]

 

[Echo North]

ok so after getting the right fuses, I went back to the beginning and heres what I got. It seems that the problem is with the input transformer.





From Mike at hairball:
Easiest way to check for signal is to use a DMM set to read AC volts.

Turn the attack pot to the GR off position. Set your input and output to mid rotation and your release fully CW.  Feed the unit a 1kHz, 0dB signal (0.775VAC).  Confirm you have 0.775VAC between input pins 2 and 3.  Now follow the signal using ground and you common reference point (where you put the black lead).  You can attach it to ground at the 0V/CT terminal at the PCB power supply.

Measure the VAC against ground at:

1. T-Pad input + (should be about half of 0.775)
2. T-Pad output +  (should be even smaller)
3. Input transformer primary + (should be the same as step 2)
4. Input transformer secondary + (getting smaller)
5. At the Input + terminal at the main PCB (should be roughly 0.06 to 0.09VAC)
6. C7 + pad (should be much larger now, around 2.0 VAC)
7. C7- pad (should be the same as  #6)
8. Blue wire on output transformer (should be a large VAC number)

Report back. That will help determine where the signal is dying.

Mike

Here are my findings:

input xlr=.776vac
Tpad in+=.392
Tpad out+=130.5
Input trans. Pri +=130.2
Input Trans 2nd+= 145.7 (here is where I see the problem, this number is getting larger instead of smaller)
Input + terminal of main PCB=.1v
I have nothing on either pin(+or-) of c7.
blue wire on output transformer=00.00
[/quote]
[/quote]
[/quote]

Input on main PCB is normal at 0.1V. The issue is likely in the "Signal Preamp" section, or with the output pot wiring.  You need to measure your DC transistor values in that section, look for cold solder/lifted pads, and double check wiring.

Mike

 

[mgalimbe]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

 

[mgalimbe]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

Checked my wiring its fine and I went over all of the solder joints in the pre amp section just to make sure. Still getting 0v at C7. Just waiting for guidance on the transistor testing.