Laney valve amp does intermittent loud pops

[rockline]

Hello,

I've got a Laney VC30-112 (valve amp).

Unfortunately, after 3 months of playing, it now produces some loud pops (even when volume is at 0 and no guitar connected). It seems that the period is every second. This makes the amp unplayable.

Could this be due to a bad valve? If so, preamp valve or power valve?

Thanks.
Best regards.

[ICBM]

Most likely a power valve - it sounds like the typical arcing they sometimes do. Buy a spare set, change them one at a time, and bin the bad valve when the problem stops. Keep the other three as spares.

[Sir Axeman]

how can he do that if 1 valve is bad...I mean aren't they all supposed to be matched for optimum performance? I had a problem when I had my last VC30 where it kept blowing HT fuses after one short blast of the amp on full volume...when the neigbours were out one day hehe. Anyway someone on here suggested an EL84 might have shorted...so try a valve change (the EL84's) which I did...actually taking the valves out of my then other amp a peavey classic 50...and voila prob was sorted no more HT fuseses going pop! But I did then buy a full set of EL84's as I didn't want to use just 1 new valve thinking they all had to be a matched set of 4...hence my wondering at mr ICBMs reply. But that man knows his onions so I just trying to understand..and be corrected in my thinking!

[ICBM]

how can he do that if 1 valve is bad...I mean aren't they all supposed to be matched for optimum performance?

Yes, which is why you fit all four new ones and keep the three good old ones as spares, but nowhere near enough to stop you troubleshooting it.

I probably should have said more completely that but I was trying to post from my phone .

One spare valve will still almost always be good enough to get you through a gig if you need to as well, even if it doesn't match. The worst that's likely to happen is that it might have a very short life if it biases hotter than the other three, but that's why you keep old used valves as spares!

I had a problem when I had my last VC30 where it kept blowing HT fuses after one short blast of the amp on full volume...when the neigbours were out one day hehe. Anyway someone on here suggested an EL84 might have shorted...so try a valve change (the EL84's) which I did...actually taking the valves out of my then other amp a peavey classic 50...and voila prob was sorted no more HT fuseses going pop! But I did then buy a full set of EL84's as I didn't want to use just 1 new valve thinking they all had to be a matched set of 4...hence my wondering at mr ICBMs reply. But that man knows his onions so I just trying to understand..and be corrected in my thinking!

If you didn't throw away the old ones, it's still worth testing them - only one will be bad. It might not be a great idea to just do it in the amp though, even if you don't mind spending money on fuses. Just occasionally, a shorting valve can fry the screen resistor as well, which then means the new valve won't work either.

[MrFoxen]

Arcing caps and bad joints can do similar noises, but in a fairly new amp, valves are the more likely. Sometimes you can see the valve flashing inside if its arcing. Not always though.