[iamthecheese]

Quote:

What do you mean when you say group terminal?
 

 
You can measure DX offset across O2 and O3 of the terminal block where power enters the amp and output exits. What is the measurement at that point?

That's where I measured from. It was the voltages I said above, around 3.5ish.
 

 

[jdkJake]

Do you have an auto ranging multimeter? If not, what range was it set at?

Just trying to establish a baseline and ask the obvious questions first.

Did you verify the correct orientation of the DC servo opamp?

 

[jdkJake]

Also, since you are testing a single board, how are you establishing a ground reference? Particularly signal ground.

 

[iamthecheese]

I'm off at college now...couldn't bring the amp along

. I will be back for labor day weekend, but I've had to put the project on hold until then. Thank you so much for your help so far, it means alot of have some sort of support line.
 
 

 

[jdkJake]

No problem. Study hard.

 

[iamthecheese]

I gotta find a multimeter since I conviently left mine back at school...but as for IC1, it is currently oriented(Tube is bottom center for reference), with the dot on the op amp in the lower right.  

 

[jdkJake]

Quote:

I gotta find a multimeter since I conviently left mine back at school...but as for IC1, it is currently oriented(Tube is bottom center for reference), with the dot on the op amp in the lower right.  

Okay, that is the correct orientation.
 
Most importantly, how are you establishing ground in your test setup? How do you have the board wired up in your test setup? A pic or two would help as well.
 
 

 

[iamthecheese]

I just installed the 2 missing components on the second board, after I wire everything up completely I'll take a couple pictures.

 

[iamthecheese]

Well partway through the wiring I decided to fire it up for kick and giggles.
 
I have a 2 stage power switch installed, so I let the tubes heat for a minute or two before turning the amp on. When I turned the switch to both on, the board I just finished light up, at that point I remember I installed LEDs under the tubes.
 
So a new symptom to add to the list is LED under board not lighting for the problem board.
 
Then I broke out my dads DMM, and the VDC between out and ground on the second boards terminal block(the one with working led under the tube) was around 2 mV and still dropping.
So then I measure LED+ to LED- just for fun, on the working board it measures 2.8V, on the problem board it measure around 0.7V.
 
Pic to come, I promise. Just gotta find the cable to hookup the camera.
 
By the time I finished typing this, I checked dc offset again, and it had dropped to .5 mV.

 

[iamthecheese]

Sorry for the poor quality...phone camera.

 

[jdkJake]

On the problem board, with the amp hooked up to the power supply (and powered on), are you still reading ~+/-30VDC?

 

[jdkJake]

While you are measuring, also measure from +LED to ground and -LED to ground. The goal is to see which of the rails is being pulled down and then find out where (or which part or solder bridge) is doing the pulling.

No offense, but, that picture is worthless. I swear, a decent point and shoot should be standard issue for these projects. Sometimes they are as equally valuable as a decent iron.

 

[iamthecheese]

Alright, found a better camera.

 
Voltage on the problem board for the LED, from LED- to G measures about -200 mV, and LED+ to ground measures about 250 mV.
 
Voltage coming off PSU is +27 and -27

 

[jdkJake]

Okay, that is much better. How about a couple of close-ups of the problem board? Which is it BTW (in the picture shown)?
 
Also, verify the orientation and correctness of V- and V+ (79L15 and 78L15). Make sure they are not accidentally swapped.
 
 

 

[jdkJake]

BTW, you should tie your AC ground directly to the chassis first prior to attempting to use the ground loop breaker.
 
Scrap off a bit of the anodizing and attach using lock washers to ensure you get good contact with the bare metal. Once you have established a good connection between AC ground and the chassis, you can then use the ground loop breaker (if required) between signal ground and chassis ground. I generally make the AC ground connection a short segment of solid, lower gauge wire as close to the AC inlet as workable.
 

 
This will make the build safer.