PEAVEY FX16 MIXER FAULT

[chrispbass]

I've had quite a lot of gear donated recently (in various states of repair) and I'm working through it with very good results. A lot of it has gone on to be used at my GF's youth music project, so nice to see it put to use rather than be scrapped off.

Anyway, I'm trying to sort out the above mixer. The SMPS was faulty, so had to fix that to be able to test the desk. Analogue side of things seems good, auxs/busses, but the master bus has no ouput. The DSP UI is working fine, but after going through the schematics, it seems that the main outs run through this section with a couple of DAC's.

I've atatched the schematics. Basically, on page 6, the outputs run through the 'feedback ferret' which is part of the onboard DSP shown on pages 56-58 and return to the master output section.
I've got signal pre 'feedback ferret' as tested from the output of U46 (page 6).

Jumping to pages 56-8, U1, U2, U3, are working ok giving an output signal, but no signal output from U7-14. The PSU's are ok (p57) but it would seem that the DAC chips U32/U35 are faulty or a perhiperal component issue, or user error!

DACS, are new territory for me, so if anyone has some suggestions reg testing, or perhaps I'm overlooking something obvious, then I'd be very grateful.

 

[NoisyIndividual]

Have you restored Factory Settings?

 

[chrispbass]

Have you restored Factory Settings?

Yes, have tried that thanks. I'm just wondering if I'm overlooking something glaringly obvious, as given the DSP board seems to be working (from a functional point of view) would it be likely for U32/U25 to be faulty?

 

[NoisyIndividual]

I'd go for the missing something glaringly obvious first before suspecting 2 chips not working.
Have you got music through a channel, (a tone can get nulled by the feedback ferret), is that channel switched to L/R, is there any audio visible with scope on the master faders (faders could be both broken), can you monitor output on headphones, or is that dead too.
Try putting a signal into a group insert and routing group to L/R, or is that not working either.
Etc.
Sorry if you've already done all this.

 

[NoisyIndividual]

There's a Media input and switch to switch this to the L/R bus. Does this work?

 

[chrispbass]

I'd go for the missing something glaringly obvious first before suspecting 2 chips not working.
Have you got music through a channel, (a tone can get nulled by the feedback ferret), is that channel switched to L/R, is there any audio visible with scope on the master faders (faders could be both broken), can you monitor output on headphones, or is that dead too.
Try putting a signal into a group insert and routing group to L/R, or is that not working either.
Etc.
Sorry if you've already done all this.

Not at all, I very much appreciate the help.

I've hooked up some music via the media inputs, but it still won't transfer to the master bus. I did however put a signal back on from the gen and I'm getting something at the top of the main faders albeit a bit squiggly for want of a better description, but varies with input level. It could well be the case that the main faders are indeed completely shot. Ive got nothing from U49 anyway.

Hopefully getting a bit closer and thanks again.

 

[NoisyIndividual]

I would be connecting the fader wipers to the incoming signal at the top of the fader track, this should bypass the faders by hard wiring them on full.

 

[chrispbass]

Yes, I'll try that and report back

 

[chrispbass]

I would be connecting the fader wipers to the incoming signal at the top of the fader track, this should bypass the faders by hard wiring them on full.

Well, another fault finding lesson today in not jumping to conclusions and 2 heads are better than one.

Took a bit of head scratching to work out the connections (as not so obvious), but decided to put a wire in like you suggested(just on one channel) et voila!!

Can’t thank you enough Noisy

Just got the unpleasant job of stripping out the pcbs to get to the faders now. Channel 1 has a broken one too, so both main boards got to come out!