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.


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.