Help? Laney LV300 Head amp problem

RevMatt

My son just bought a second hand LV300H – his first proper amp, so no need to say ‘he was excited’! It’s a great amp that does exactly what he wants, but within a day of buying it we discovered a problem.

I have contacted Lany direct about this, and will await their reply, but I know there are some very techie and knowledgeable people here, so maybe you can offer some thoughts? 

 

The issue first occurred on channel 2 (mid gain channel) with the volume on about 4 and the gain on about 7-8. All of a sudden the amp spluttered and crackled, almost like poor connection on the jack, and immediately the guitar volume cut to very quiet and a loud hum overwhelmed the guitar volume. Sometimes, switching channels or unplugging the guitar and plugging it back in again resolved this, but sometimes the loud hum (and reduced guitar volume) persists. We then noticed that the same issue occurs on the 3rd (high gain) channel.

 

Essentially, that describes the issue, but it may help to know, that when turning the amp on (with volumes set to zero and no guitar plugged in) I hear a very faint ringing (a bit like hall reverb). This continues until you turn up the selected channel’s volume (still with no guitar connected), at which point the ringing stops and is replaced by a low hiss/hum which I would say sounds fairly normal. When the volume is returned to zero the quiet ringing returns?

 

Thanks...

ecc83

ICBM and other techs will no doubt have deep knowledge of the amplifier but if the problem is confined to channel 2 then it could be the single ECC83 valve in the amplifier.

Since the amplifier is second hand it might be worth contacting the vendor ASAP because if it needs to go into a shop it could be quite expensive to sort out.

Dave.

ICBM

What Dave said.

If it's a problem on the distortion channels it's likely to be the valve - either faulty or not making proper contact with its socket. If it's not, it's likely to be a bad connection somewhere in the circuitry for those channels, so it shouldn't be expensive in parts, but these things can sometimes be time-consuming to find. I've never worked on one of these, so I don't know whether it's an easy or difficult amp to disassemble - or if that means removing the PCB, which it often does.

If you bought it from a shop, I would ask them to sort it out. If you bought it privately you're probably less likely to get the seller to fix it, but worth a try. Failing that, the first thing is to check that the valve is securely seated in its socket - if you can get at it simply by taking the back panel off.

RevMatt

Thanks for the replies so far, it's good to get some more knowledgeable input on this. The amp was bought privately and although the seller was very pleasant to deal with I have no warranty or anything. I did remove the amp chassis from the head box last night and everything looks very clean and in good order and the components are easily accessible. I didn't replace the valve but I do have a couple of spares so will try that tonight. Will keep you posted...

DJH83004

On this amp, the clean channel is purely op-amp driven (TL072), but the Drive 1 & 2 are fed onto a separate PCB with an ECC83 and to/from ribbon cables, so this would be the area to focus on initially. The one I worked on had a similar problem but across all channels which turned out to be the input jack and broken PCB tracks.

RevMatt

Valve replaced and no issues so far (still the low level ring when the volume is down but that could be normal), but the issue didn't occur last night until the valve had been on a long while - so far it's just had 30 mins of play time so maybe not long enough to be sure....

@DJH83004 - is this what you do for a living, and if so, is a repair like that economically viable?

DJH83004

@RevMatt yes I run a small amplifier repair business in Nottinghamshire, so if you did want it checking over that wouldn't be a problem - but, I'm just recovering from some fairly major bowel surgery, so am out of action at the moment, but more than happy to give you a few pointers via the forum, if that helps. 

RevMatt

Small world, I'm in Nottingham... Sorry to hear about the health but if you let me know when you're taking customers I may be in touch. @DJH83004

RevMatt

This has been okay since replacing the valve so hopefully job done. There's still a chance that under prolonged use the problem may return as the amp hasn't had that much use since the valve change but fingers crossed...