M3500 console meter issue

[brendanh]

Anyone have any ideas what might be causing the meter in channel 13, and also the Peak led on the VU meter to be lit up even when there is no signal going into the console, see attached pic..
I tried plugging a drum mic into channel 13 and the meter maxed out even with channel input gain turned all the way down and pad switch pressed in. I haven't yet had a chance to test if the audio is ok through this channel. But both meters remain the same even when there is no mic lead plugged in.

Any ideas or help anyone can offer is appreciated.

 

[witzendoz]

Need a bit more info,

When you plugged the mic in did the channel have noise as well as the pegged meter?
Need to know if audio is getting through.
Alan.

 

[brendanh]

Hi Alan,

At this point I can't say if there is any noise or not. I bought the console 2nd hand and only just powered it up for the first time. I have channels 1-8 routed into my interface using the direct outs on those channels on the console and the audio through those seems fine. However I'm yet to test the audio through the affected channel by hooking it up to the interface, will do so in the next few days and let you know what I find.

 

[brendanh]

Hi Alan,

I've routed the the audio into the channel and out through the direct out into my interface, and it seems to work fine, I can't hear any unexpected noise and seems to be plenty of the audio I want.

The peak led on the vu meter seems to flicker on and off intermittently bust mostly just stays on, even when there is no signal being input into the console

 

[witzendoz]

Sounds lie it could be a loose/dirty connection on an internal ribbon cable?

Alan

 

[wkrbee]

Most likely a op-amp in the meter circuit failed,slamming the output to the meter to the power rail

 

[brendanh]

Thanks mate, any ideas on tracing the issue to find the faulty part?.. Sorry my electronics knowledge is fairly limited.

 

[wkrbee]

A slammed opamp would cause the meter to peak and then fall back on power up.

 

[brendanh]

Yeah I'm not real sure how to diagnose or find the faulty op amp, so I've just been using that channel for talkback