Amp problems... help

dezb1 · Post by **dezb1** » Tue May 20, 2014 9:36 pm

I'm having trouble with my Laney VC15 I've had the amp for a few years, and today while playing the volume on the clean channel just dropped out there is still sound but its very quiet even when the clean volume is set to 10. The drive channel is working as normal.

any ideas what's gone wrong...?, I have no clue on the workings of a tube amp... other than it has something to do with electricity

Post by **Mike** » Wed May 21, 2014 9:06 am

Have you got any spare preamp tubes you could pop in to eliminate those?

it's weird though, from what I can see from the manual you have 3 preamp tubes

V1A is used by both clean and dirty
V1B is used by dirty channel only
V2 is used by both (second gain stage)
V3 is the phase inverter

So your symptoms are strange. If V1B was bad you would have OK clean but no dirty channel
If V1A is bad you should have nothing at all.

But you have dirty fine and no clean - suggests V1A is ok.

Hmm - still would be my first port of call, replace V1.

sunshiner · Post by **sunshiner** » Wed May 21, 2014 9:21 am

Peamp tubes, as it was said, though I'm not a specialist. By the way, how loud is VC15 if to play with a drummer, I mean cleans or slightly overdriven sound? I have MIC Laney Cub 10 it has good cleans to my ears, but they are not loud enough.

gusman2x · Post by **gusman2x** » Wed May 21, 2014 9:28 am

My VC15 would just die after 20 mins, and then come back to life after another 20. It was a polyswitch that needed replacing. Got it done by an amp tech for Â£60. Don't know if this is the same problem as yours (perhaps not by the sounds of it), but the polyswitch is a very common fault on the VC15s.

dezb1 · Post by **dezb1** » Wed May 21, 2014 11:08 am

I don't have any spares, total noob when it comes to amps what tubes would you recommend as replacements? And what does a polyswitch do?

gusman2x · Post by **gusman2x** » Wed May 21, 2014 12:08 pm

Polyswitch Info

A polyswitch is basically a resettable fuse. I think it just trips out over a certain load (maybe temp?) and then bypasses again once the DANGER has gone. I think in this instance, they're thermistors, and activate when the temp runs too high. This is why when it's left off for a while it comes back to life fine.

What I should have said ref issues with the polyswitch is that when it happens, the circuit completely dies. The sound just fades out, and the power does not get to the tubes. So when I looked in the back, none of them were glowing. Might be when you have the issue you could do a quick look see and see if any tubes are not glowing, flickering, or duller than the rest? I might be talking out my arse on that though, so sorry if it's not helpful enough.

The amp tech I took it to said as long as the cost of the repair is lower than the resale value, it's worth it.

Post by **Mike** » Wed May 21, 2014 1:20 pm

dezb1 wrote:I don't have any spares, total noob when it comes to amps what tubes would you recommend as replacements? And what does a polyswitch do?

They're all good - just pick up some standard's (EHX, JJ's whatever) from hotrox - they ship fast.

dezb1 · Post by **dezb1** » Wed May 21, 2014 8:19 pm

Had a look at hotrox, they sell jj ecc83s and ecc83 gold pin. The manual says v1 is ecc83 high grade and valves 2 & 3 are ecc83 standard. Am I right in thinking I need one gold pin and 2 standard? What makes a high grade high grade?

http://www.hotroxuk.com/matched-valves- ... 188-0.html

dezb1 · Post by **dezb1** » Wed May 21, 2014 8:59 pm

Watford valves sell a set especially for the vc15

http://www.watfordvalves.com/product_d ... sp?id=2392

Are they the same valves as these? (only more expensive)

http://www.hotroxuk.com/electro-harmonix-12ax7.html

oh and which bits is it inside the amp that can kill you? (I'd rather not die)

sorry for the multiple questions, like I said I know nowt about all this...

Post by **Mike** » Wed May 21, 2014 9:30 pm

Always thought Watford valves were a rip

You only need two valves for v1/2

Just get something reasonable cheap initially
Don't get a set from Watford valves fuck those guys

benecol · Post by **benecol** » Wed May 21, 2014 9:33 pm

Mike wrote:Always thought Watford valves were a rip

Don't get a set from Watford valves fuck those guys

Have always felt the same way. Dreadful arseholes. Fuck those guys.

Voc Rock on eBay is my favourite, though. They're lovely.

dezb1 · Post by **dezb1** » Wed May 21, 2014 9:54 pm

Mike wrote:Always thought Watford valves were a rip

You only need two valves for v1/2

Just get something reasonable cheap initially
Don't get a set from Watford valves fuck those guys

I was going to buy from hotrox I was just checking that the EHX 12ax7 valves were the correct ones... But I though I needed 3...

honeyiscool · Post by **honeyiscool** » Wed May 21, 2014 10:00 pm

dezb1 wrote:
Mike wrote:Always thought Watford valves were a rip

You only need two valves for v1/2

Just get something reasonable cheap initially
Don't get a set from Watford valves fuck those guys
I was going to buy from hotrox I was just checking that the EHX 12ax7 valves were the correct ones... But I though I needed 3...

The EH 12AX7 are pretty damn great. There are like three companies that seemingly make all the new tubes in the world. New Sensor makes all the Russian ones, like EH, Svetlana, Sovtek, etc. JJ makes the Slovakian ones. And then there are the Chinese tubes, which I think are Shuguang. They're all pretty good, but I like Svetlana preamp tubes and Electro Harmonix power tubes. You don't really even need to worry about which kind of tubes in which position either. The standard 12AX7 from Russia will work in any position.

honeyiscool · Post by **honeyiscool** » Wed May 21, 2014 10:05 pm

From the pictures of the VC15 on the Internet, it seems like there are three 12AX7s and two power tubes (EL84, looks like).

It never hurts to have more tubes than you need, but there's little chance that you need all three replaced. Since only one of the channels is misbehaving, chances are you only need one replacement tube. VC15 seems to have a tube guard you screw out, but once you do, it looks like super easy to reach any of the tubes. I would honestly just take one out, replace it, play the amp, then turn it off, and rinse and repeat until I know which tube is bad. It's not a halogen lamp so your fingerprints aren't going to hurt it, so don't worry about that, either.

But after you do all that, I HIGHLY recommend buying an entirely new set of tubes, the entire 3x12AX7 and 2xEL84 (matched pair) set. Then, install them. If anything ever goes wrong, your current tubes become your emergency set. I do this with every new amp I buy.

dezb1 · Post by **dezb1** » Wed May 21, 2014 10:07 pm

1 more question... When I plug my guitar into the FX loop return the volume is substantially louder does this prove or disprove anything?

NickS · Post by **NickS** » Wed May 21, 2014 10:21 pm

Proves your problem is before the FX loop return, so not a phase splitter problem like our rhythm guitarist seems to get every couple of years on his Fenders. In the case of the Marshall JTM60 it's often the FX loop jack sockets. Check this by running a patch cable between the out and the return. If not this, go for swapping preamp valves. If this doesn't help you've got a problem that needs amp skills - bad solder joint, dead decoupling cap, etc.

dezb1 · Post by **dezb1** » Wed May 21, 2014 10:32 pm

So judging by the diagram in the manual ( http://www.laney.co.uk/uploads/004115e1 ... 280462.pdf ) if it's a valve it's has to be valve 2 as if it was valve 1 there would be no sound and valve 3 is after the fx loop... Is that right?

Post by **Mike** » Thu May 22, 2014 8:18 am

dezb1 wrote:1 more question... When I plug my guitar into the FX loop return the volume is substantially louder does this prove or disprove anything?

Proves you don't need to worry about V3 (PI) like NickD said.

Just get yourself two preamp valves and swap about V1 & V2

dezb1 · Post by **dezb1** » Thu May 22, 2014 8:36 am

Mike wrote:
dezb1 wrote:1 more question... When I plug my guitar into the FX loop return the volume is substantially louder does this prove or disprove anything?
Proves you don't need to worry about V3 (PI) like NickD said.

Just get yourself two preamp valves and swap about V1 & V2

cool that's them ordered, cheers for the help chaps.

Post by **Mike** » Thu May 22, 2014 9:27 am

Here's hoping that's it, in my experience 8 times out of 10 some new tubes will sort it.