Driver Test Issue [resolved]

[ArtnShit]

Hi,

First off, sorry for flooding this forum with build questions!

Driver Test on page 65

I am running into an issue testing the driver boards - A socket is totally fine. D socket the potentiometer is not lowering the voltage or changing it at all according to my meter. Any ideas?

Thanks!

 

[Paul Birkeland]

What are all the voltages on that PC board?

 

[ArtnShit]

The other voltages are all appropriately in their ranges. I dont have the exact ones off the top of my head but IA was around 518 and OA at 298.

The A-side was totally fine for all tests and I was able to dial into 175.

 

[Paul Birkeland]

Well when you get a chance, post IA, OA, IB, OB, KregA, and KregB for that board.

-PB

 

[ArtnShit]

Here are the socket D readings:

IA 521
OA 298
IB 298
OB 277
KregA 0
KregB 6.75

 

[Paul Birkeland]

There's a pad labeled "X" on the Kreg B side, what do you see there?  There are a few different debugging paths that will depend a bit on what appears there.

 

[ArtnShit]

I am getting 0

 

[Paul Birkeland]

Can you post a photo of the top and bottom of the C4S driver board on that side of the amp? (0 isn't what I was expecting!)

 

[ArtnShit]

Here's the board!

 

[Paul Birkeland]

You have both white wires from the 9 pin socket going to one of the Kreg set of pads and nothing connected to the other side?

 

[ArtnShit]

There it is! Moved white-D8 to kreg B-side and all is working well now!! Thanks so much, you solved it.

Is it ok that the voltages after adjustment with the potentiometers shift to stuff like 174.8 and 175.3?

Thanks again for taking the time to help me out!

 

[Paul Birkeland]

Sure, they just need to be close.  I'm glad you got it sorted out and that was certainly about as harmless as miswires come!

 

[Paul Joppa]

I'd like to see those voltages +/- 5%, to keep the driver operating in the "sweet spot." You're fine.

Incidentally, that voltage will drift a bit as the tube's cathode material settles down, so re-setting it after the first 100-200 hours is a good idea. After that it should be pretty stable for a long time - check once or twice per decade ...  :^)