Soundcraft 500 VU meter peaked

[dungeonnmaster2]

Greetings,

New to the board I hope this is correct procedure...

I picked up a Soundcraft 500 series 24 channel console. It's in really great condition with not one noisy pot or fader.
The only trouble is that the #1 VU meter (has 8 group out VU's & L-R Mix out VU's) is peaked with the red peak LED
on as soon as it is powered up.
I have checked all channels, groups & aux. & it all works great with no hum or noise anywhere.

I haven't taken anything apart yet. I wanted to get an opinion from someone before I do. Should I just try find a replacement?
Or try to find a fix?

Doesn't seem to effect anything other than being annoying... And of course you can't meter group #1 

Any help is much appreciated.

 

[moamps]

Hi,
please download the schematics from here:
http://soundcraft.com.s3.amazonaws.com/downloads/user-guides/500-600-user-guide-3-4.pdf
and check Opamp and transistors in corresponding VU meter driver  (page 20).
Regards

 

[dungeonnmaster2]

Thanks for your reply, I'll check that.

 

[PRR]

The meter is probably fine. (The needle and LED are different circuits.)

Somehow that channel is making MAXimum signal all the time. If you don't hear it, it may be supersonic. This could be unwise mods, bad power capacitor, or all sorts of things. 'Scope and finger may be the best tools.

And welcome.

 

[PRR]

**Gently** tweak the trimmer for the affected meter/LED. If the trimmer wiper has lost contact, the op-amp will throw huge DC into the meter, pinning it. Depending on op-amp type, this DC might also be in the direction to turn-on the LED. (Ah, the op-amp is TL072 and we don't know which-way the error will go).

Bad wiper contacts are VERY common in old gear. Tweak it *just* enough to see if it comes into proper action (meter at 0%/-20VU with no signal). If you turn a lot the calibration is screwed-up.