Loud noise and no other output from amp

Dr_Necessiter

So I'm a numpty but I'm looking for opinions as to why:

I've just changed the valves and speaker on my Laney LC30 MkII. The valves are a straight replacement set from AmpValves.co.uk, being "Replacement Valve Kit For Laney LC30 112 (3 x ECC83 1 x Balanced ECC83 4 x Matched EL84)". The balanced valve is in the VB 4 position (4 from the right) and the speaker is the original Celestion 70/80 put back in after an earlier play with a different one. All I'm getting when I switch from standby is a loud noise as though it's about to feedback but without the high pitched squeal and this is continuous.

I've double checked that I've not connected the speaker arsey-versey and the valves just have the normal pale glow of those in an amp that isn't working very hard. All are lit.

I've fitted the valves the only way that they will go in and I understand that the valves don't need to be biased in this model.

I'd be very grateful for any thoughts please.

ecc83

Pull the PI ECC83 (V3 I think) and see if that stops it. If so, replace it and move back through the valves to the front end. I don't hold out much hope of a cure though, you might have disturbed a bad joint on a valve base.

BTW "balanced" double triodes are a total waste of money IMO.

Dave.

ICBM

The PI should be V4, the balanced one. If you pull that first and the noise stops, the fault is in the preamp.

The easiest way to tell if it's a valve issue is to simply replace each of the new ones in turn with the old ones - or do them all at once if it's easier/quicker - making sure you keep a note of which one goes in which position. If it works with the old valves then one of the new valves is faulty.

As Dave says, a balanced valve for the PI is a marketing con, but that's not the cause of the trouble.

Dr_Necessiter

Thanks gentlemen, I'm not with the amp at the moment but will give this a go later.

Dr_Necessiter

Swapped all of the valves back but no change. Looks like it's off for a trip to the amp doctor.