Digitech guitar talker pedal problem

[bigdrums925]

I have this pedal that you plug the guitar and a microphone into, and there are outputs for the guitar am and to the PA.
It has started sounding (sort of) strange and not acting as it did.
I noticed after taking off the cover the LED labeled DSP Audio Overfolw. That's the label on the board next to the LED that begins flashing
anytime the power is applied. Can anyone comment on what this might indicate and a possible remedy?
Can't find a schematic for it

[Mick Bailey]

Quite a few DSP devices have an overflow warning, usually to indicate excessive levels or (in the context of a delay) excessive feedback being applied. My understanding is that a mathematical overflow is being created within the processing. What I don't know is whether the flashing LED is normal or not, but it may be a good idea to contact Digitech. The last time I asked them an in-depth technical question it took a while, but I did get a well-considered and helpful reply.

Are all of the modes acting strange, and what's the exact nature of the problem?

[Jazz P Bass]

DigiTech Talker

"It has started sounding (sort of) strange and not acting as it did"

That sure helps narrow it down, now doesn't it?

Is this the unit in question?

[bigdrums925]

Yes, the attached pdf is the same unit I am working on. Sorry for not being more descriptive about the nature of the sounds made now as opposed to when it worked more or less properly. Each of the 6 "patches" had a distinct effect on the unchanged sounds of voice &/or guitar as in the bypass mode. Now all 6 sound more/less the same, which is like an untriggered gate where just a small amount of the signal passes through. Sounds like it's struggling to pass the signal, kinda like crunch and gate together with the gate adjusted too tight for normal audio. It's hard to accurately describe the sound.
I suspect the flashing LED is not flashing in normal operation and is an indication of the source of the problem. I have no digital experience however. So was looking for any suggestions as to what the flashing LED is indicating.
I will try contacting Digitech and see what they have to say about it. As always, Thanks!

[Mick Bailey]

My first instinct with older pedals is to check the electrolytic caps for bulging or leakage. Sometimes they leak their contents which can cause odd behaviour by establishing low-resistance paths between adjacent tracks. I've had quite a few like this. It's also essential to ensure the DC voltages are correct. Most processors fed with a too-low voltage will continually test the voltage and reset in an attempt to stabilize. This is a common failure with the Whammy pedal, for example. I'd be looking to see what voltage regulators are fitted and make sure the outputs are correct and ensure that these are actually getting to the devices.

Processors are pretty robust and I usually find it's some support logic or signal-conditioning part of the circuit that's at fault with this type of gear - assuming that the voltages are stable.