S.E.X. upgrade C4S problem [resolved]

[sprout]

My S.E.X. amp sounded great on headphones before the upgrade installation, but only after a right channel failure that was resolved with a better solder joint at a loose spot. However, after the upgrade, I get 90 v at OB, but get only 1 v at OA. Again a right channel issue, so I don't know if this is an original problem back again, or if it's an upgrade problem. Advice please! Thanks, Jim

 

[Paul Birkeland]

I would post build photos.  1V at the output of a C4S would have me looking for metal bits touching each other that shouldn't be (don't forget that the chassis plate counts).

 

[sprout]

Again, after some solder joint work, I got a correct reading, hooked it up, and it sounded great. Then after half hour of Doobie Brothers, the right channel dropped out. Now I'm getting 1 v at OA again.

So, both before and after the upgrade, I had the right channel drop out. I plan to keep re-soldering each joint on the right channel.

I'll try photos, but it didn't work last effort. It looks like a monkey made it.

Thanks and very sorry to be a pest. Jim

 

[Paul Birkeland]

R1 on the A side isn't well soldered, could I see photos of the bottom and top of the PC board?

 

[sprout]

Thanks, I'll re-solder that one. Here are photos of the board, and it is so small, maybe there's contact somewhere.

 

[Paul Birkeland]

There are definitely some soldering issues here.
https://www.youtube.com/watch?v=EN16Pi7pcfk

The center leg of the MJE5731A on the left side of the photo you posted is probably the worst of the joints on there.

 

[sprout]

I added some solder and now it works again and sounds great. Thanks for all the help. Here's how I painted the top.