TOA D3 Mixer - "Clip" lights stuck on

[earache]

Hi There

I have a TOA D3 mixer that, on channels 3 and 4, the "clip" lights stay on. What is it that lights the "clip" LED when there is no signal?

I think this is the relevant page of the schematic...I couldn't post the whole thing, it was too big. It details channel one and states that the other three channels are carbon copies of channel one.



Thanks for your time and interest!

[Jazz P Bass]

That file is unreadable.

[The Dude]

That file is unreadable.

Yes a screenshot won't do. Upload the actual .pdf or zip it and upload it.

Without being able to see it, my best guess is that whatever makes up the first gain stage in from the input jack is bad- be it a pair of transistors, op amp, or whatever.

[earache]

Here's another try at something readable:



Here's a try at zipping the whole file:

D-3-SM-_E.zip

[MarkusBass]

Shorted Q101, or Q102 will cause that the LED is permanently on.

Mark

[Jazz P Bass]

To add: If the M101 opamp is bad, and it is outputting a constant high on the output pin (pin 1), that will turn on the clip led.
Lifting D103 will prove out that theory.

[earache]

The owner of this mixer also had a "more broken" one as a donor, so after lifting D103 to no result I replaced Q101 and Q102 on channels 3 + 4 with direct substitutes from the donor. No more stuck clip lights!

Thanks for your help everyone!

[MarkusBass]

Now it's the time to fix the "more broken" one

Mark