B-side C4S board issue at voltage check [resolved]

[Paul Birkeland]

I would be interested in seeing the 7 pin socket on the offending side.  Does the tube glow in that socket?

-PB

 

[PassionForSound]

Here are some photos of the D socket. I've included one to show that the red wire attached to pin 5 isn't shorting with pin 6 because it looks like it from above.

https://photos.app.goo.gl/udjU7uq8tuPffGGp6

https://photos.app.goo.gl/TBWDe7YvHztAb4ws8

https://photos.app.goo.gl/jzS4HsLnNmGgvZGs5

 

[Paul Birkeland]

Does the 6AQ5 glow in that socket?

 

[Tom-s]

I've had issues with a C2A build where it was all related to the 6AQ5's not biassing properly on first power on. Switching them from side to side got the sleeper to fire up.

 

[PassionForSound]

Does the 6AQ5 glow in that socket?

Yes. Glow test passed on all tubes (and still does). Swapping tubes also had no impact

 

[Paul Birkeland]

Can you verify that the resistance of the little blue resistor between 5 and 6 on that 7 pin socket still measures appropriately? 

 

[PassionForSound]

Can you verify that the resistance of the little blue resistor between 5 and 6 on that 7 pin socket still measures appropriately?

236.2 ohms measured in-situ

 

[Paul Birkeland]

This should probably come visit my bench and I'll have a look over it.  As a last resort, if you had a broken wire between the high current C4S OA and pin 5 of the 6AQ5 socket, I suspect you'd end up with this issue as well.

 

[PassionForSound]

I'll rewire OA and D5 first and then it'll be time for a return trip

 

[PassionForSound]

For anyone following along at home, this kit ended up making the long trip from Australia to the USA over the Christmas break. I'm looking forward to an update from Paul when he has time to look at it (I believe he was quite swamped at the time so I appreciate the offer of assistance).

 

[Bourney]

I’m following along from home and keen to hear how the mystery is solved.

It will be a well travelled amp by the time it returns to you. 

 

[Bourney]

Has the mystery been solved? Does the Crack-a-two-a live?

 

[Paul Birkeland]

I found a large solder blob had migrated through one of the C4S PC boards and up against the body of an LED, which destroyed the LED itself.  I replaced the two LEDs on that side of that particular PC board and that was all that was required to repair this C2A.