ampeg svt bias and balance LEDS going wacky

[Ant]

hey hey, yeah the balance and bias leds on the back of my svt keep going on and off, and dim sometimes, usually if i flick the standby switch or sometimes when playing.

whats that all about then? it still sounds the same though.

[Dood]

I believe the BIAS LED circuit constantly checks the bias of the power amp valves - and *can* flicker when you are playing. However, if you have had the amp on for a good 20mins or so and it is idle, I would expect the LEDS to remain constant. I *did* read somewhere - maybe talkbass that earlier versions of the circuit were a bit untrustworthy - however, I never had any probelms with my SVT2al the time I owned it. It was a 99 Black Face.

You could try swapping the valves out and rebias to see if that helps - ok, so thats expensive - unless you can borrow a set?

[umph]

[quote name='Ant' post='853707' date='Jun 1 2010, 03:57 PM']hey hey, yeah the balance and bias leds on the back of my svt keep going on and off, and dim sometimes, usually if i flick the standby switch or sometimes when playing.

whats that all about then? it still sounds the same though.[/quote]
valves pull current when there pulling signal which shifts the grid current and changes the bias reading.

Edited June 2, 2010 by umph