Eden Nemesis SC-250 no output to speaker

[xtian]

I have an SC-250 on the bench. All voltages look good, and signal is present at headphone output, but no signal at speaker output jack. None of the power MOSFETs are shorted, and amp is running cool, not drawing excessive current.

I do see 0.33vDC where the large !! are shown on the schematic.

How can I troubleshoot the power amp section?

Could the mute function be engaged? How to test?

Here is the schematic: http://music-electronics-forum.com/a...-sch-final.pdf

[Jazz P Bass]

I see that the 'Ext Spkr' jack has a 'normally closed' contact that provides a ground path for the 'Internal Speaker'.
Make sure that the connection is good on those contacts.
If they are open, then you will not have a ground for the speaker.

Also, I would check that 'Speaker On/Off ' switch along with the thermal switch.

[g1]

Looks to me like the mute is pre-headphone, so if you have signal there the mute should be ok. (FQ102 right after master).
Is the speaker switch and thermal breaker in series with it good?

[xtian]

Good suggestions, thanks.

Now I've looked more carefully at the output wiring, and see that the internal speaker is wired in series. So while I was testing without the internal speaker connected, the external speaker jack was non functional but I didn't know that.

I've reassembled the amp, and everything's working fine!

I didn't mention that the customer brought the amp disassembled saying there was no output. Hmm....