Peavey Bandit (2007) no reverb

[camarada78]

Hello,

I have a Peavey Bandit on my bench that works fine but the digital reverb is gone.

Schematics attached.
I traced the signal and it is indeed getting into the Reverb board but its not getting out of it.

- all voltages seem correct (1.8v, 3.3v and 5v), the regulators are working.

Anyone experienced with this unit?


Thanks, have a good day

 

[JohnRoberts]

That was years after I left Peavey but in general look for something obvious with a close visual inspection.

Not many moving parts.

JR

 

[NoisyIndividual]

I would be looking at the PCM3010.

Does it have analogue in Pin 1?
Does it have the clocks on pins 10/11?
Does it output digital to the DSP pin 13?
Does the DSP send data back pin 12?
Is there any analogue output on the output pins 22/23?

 

[camarada78]

Yes there is analog in pin 1. No there is no audible output on pin 22/23. Should be also analog? I might have misunderstood the datasheet. I think it was just digital out there. Anyways, scope says it has little to no noise signal on 22/23. i will check the data pins.
so far its the primary suspect.

 

[NoisyIndividual]

You forgot the bit where the PCM sends data to the DSP, and the DSP sends it back.
If this doesn't happen, neither will the output.
i.e. it could be the DSP.


Ah, sorry, missed the bit where you said you would check the data pins ....

 

[camarada78]

Nothing on DSP pins 10/11/12, just noise if i really zoom in the scope. Pins 13/14/15 have a similar but regular spark peaking around 100mV every 4 microseconds, nothing like the digital square pulse on the datasheet. Since pins 14 and 15 are grounded i presume this spark is "noise".
Since all voltages are getting to it but it is not outputing nor digital, nor analog signal, i would take the risk and replace this chip.

 

[NoisyIndividual]

Pins 10/11 are clock INPUTS that need to be there for the PCM chip to work and sync to the DSP circuitry producing them.
Pin 12 should be data coming back from the DSP.

None of these signals seem to be coming from the DSP circuitry, so the problem likely is there, not the PCM chip.

The PCM is unlikely to produce any digital output stream Pin 13 if these clock signals are missing.

 

[NoisyIndividual]

This could be something as simple as a faulty C206 on the reset line preventing the DSP from running.

It might be worth checking the DSP to see if it itself has a working clock, and/or is not held in reset as described above, or some similar Halt situation.

 

[JohnRoberts]

It will not be easy to speculate about the inner workings but certainly worthwhile to confirm that it is running (clocking).

It could be simple, just not obvious.

JR

 

[NoisyIndividual]

U201 pin4 is the reset line. This should be +ve.

Funny how this whole system depends on the integrity of C206 for the DSP to run, given we all know these caps fail long before the DSP chip does.

 

[Khron]

Also check the clock on pins 2 & 5 of U202, and that it also reaches pin 16 of the PCM3010 and pin 97 of the DSP (should be the 8.192MHz the quartz crystal is rated at; that being said, even the quartz itself could have potentially failed).