No sound / fault finding Ashdown perfect 10 combo

[kingforaday]

Hey, I have an old ashdown perfect 10 bass combo. I got it free years ago because it didn’t work, it’s not really worth anything but I’m always interested in learning how to fix things. 
 

It power on but no sound (not even hiss from the speaker). I’m getting sound from the headphone and external speaker jacks and everything seems to work well that way, but nothing at all from the built in speaker. I tested the speaker separately and that works fine. 
 

what would be the next thing you’d check?

 

 

Edited April 5 by kingforaday

[Bigguy2017]

So, the speaker output jack works into an external cab? Therefore signal must be present at the jack socket.

 

Take a close look at the speaker out jack socket - if it's the switching type make sure the contacts are closing without a jack in place - push down on the contacts.

 

Pull off the red + blk speaker spade connectors at the PCB end (LS1 + LS2) - with a DVM check for continuity to the speaker.

If no DVM then put a AA battery across these terminals - speaker should click...

 

I can't find a schematic for this combo - Ashdown will supply one I'm assume...

[kingforaday]

4 hours ago, Bigguy2017 said:

So, the speaker output jack works into an external cab? Therefore signal must be present at the jack socket.

 

Take a close look at the speaker out jack socket - if it's the switching type make sure the contacts are closing without a jack in place - push down on the contacts.

 

Pull off the red + blk speaker spade connectors at the PCB end (LS1 + LS2) - with a DVM check for continuity to the speaker.

If no DVM then put a AA battery across these terminals - speaker should click...

 

I can't find a schematic for this combo - Ashdown will supply one I'm assume...

Thanks for replying, yeah I’ve tested the speaker both with a multimeter and audio tested it with a different amp. So the speaker is fine, I did try cleaning the speaker out and headphone jack sockets as I figured they were maybe dirty enough to be falsely stopping the signal (as if a jack was plugged in). That made no difference… Perhaps I should have another go! I just expected some kind of result from that and when I didn’t get one, I wasn’t sure where to look next!

[Stub Mandrel]

On the vast majority of solid state amps the headphone disconnects the speaker output and powers the 'phones via a series resistor. This means your fault is probably, as you seem to realise, a break somewhere in the output wiring, not in the electronics.

You have a suitable instrument to trace the fault. Put the meter on an a/c range, perhaps 20vac or more.

 

With one probe at a good ground point, carefully probe from the headphone socket to the speaker leads.