Repairing a Laney LC15R - help and advice needed

imalrightjack · August 2014

Hi all,

I've just picked up one of these very cheaply. It switches on, the valves all light up and it gives a signal. The pots crackle like hell, the gain in particular, but the biggest issue was the dead reverb. I unscrewed the reverb tank from its hideously dusty tolex cover and, after jiggling around with the red/white cables, found it actually works...a bit.

Questions:

What advice do you have on cleaning up crackly pots?

Can I connect this reverb tank to my Engl Gigmaster (it's easily accessible and has red/black cables connected which presumably are the inputs and outputs like the Laney one)? Are there voltage issues at play?

Any advice welcome. I'd love to restore this as what little sound I got was actually very nice.

I imagine @ICBM can help

Thanks,

Steve

jd0272 · August 2014

Sounds a bit like mine...........

ICBM · August 2014

Crackly pots - contact cleaner/lubricant (Servisol, Electrolube, Maplin own brand) - and if that fails try WD40, but not first. Squirt it into the pot casing either through the slot at the bottom or the little notch in the side, whichever you can reach with the tube that comes with it.

You should be able to test the reverb unit by connecting it to the Engl, but it's unlikely to the fault if it works 'partially' - they either work or they don't usually. Make sure it's connected the right way round - you can identify the cable that should go to the Out end if you unplug both of them and touch the tips with the amp on - the ones that buzzes goes to the Out. There are no dangerous voltages.

Danny1969 · August 2014

I would change the pots they don't cost a lot. From memory these amps have phono connectors to the tank and the PCB so you need to clean both ends really

imalrightjack · August 2014

Cheers, guys.

ICBM · August 2014

I would definitely try cleaning the pots before even thinking about changing them. They're not that expensive, but they are a pain to do since you have to take the board out, and why change them if cleaning them fixes it? Assuming it does of course - but that's why it's worth trying WD40 if contact cleaner fails, since you have nothing to lose at that point.

imalrightjack · August 2014

Sage advice as always, @ICBM.

imalrightjack · August 2014

I'm trying to replace the HH Invader speaker and got one nut off but the other three just keep turning. Any advice?

ICBM · August 2014

imalrightjack said:

I'm trying to replace the HH Invader speaker and got one nut off but the other three just keep turning. Any advice?

Hold the bolt with a pair of pliers, end-on so the jaw serrations don't chew up the thread if you can avoid it - that will make it difficult to get the nut right off.

Or if you have any more nuts of the right thread, use a couple as locknuts to hold it in place with one spanner while you undo the main one.

Patience required. It can be a real pain.

imalrightjack · August 2014

Managed to get one off by pushing through the grille cloth. Two proving to be real buggers! Thanks.

ICBM · August 2014

Can you get a screwdriver through the weave of the grille without damaging it?

Once you've got the speaker out, soak the baffle around the screws with superglue, it will (hopefully) stop them coming loose again.

imalrightjack · August 2014

I've got one left to go but I'm through the cloth and it's still spinning...like my head! It's such a small screw, there's not much I can do to clamp or anything.

imalrightjack · August 2014

Eventually hacksawed off the final bolt/screw and put in two new screws without nuts either side of it (on the new Greenback, which sounds great).

timmysoft · August 2014

ICBM said:

Crackly pots - contact cleaner/lubricant (Servisol, Electrolube, Maplin own brand) - and if that fails try WD40, but not first. Squirt it into the pot casing either through the slot at the bottom or the little notch in the side, whichever you can reach with the tube that comes with it.

You should be able to test the reverb unit by connecting it to the Engl, but it's unlikely to the fault if it works 'partially' - they either work or they don't usually. Make sure it's connected the right way round - you can identify the cable that should go to the Out end if you unplug both of them and touch the tips with the amp on - the ones that buzzes goes to the Out. There are no dangerous voltages.

I wouldn't use wd40, it leaves an oily residue that attracts dust! Something like the interflon tf is a much better solution. I used to work on subsea oil and gas terminations, so I've seen the longer term effects on pcbs and potentiometers with using wd40.

thermionic · August 2014

I thought the best way to mount speakers was to use t-nuts on the front of the baffle and bolts from the back? The t-nuts have little teeth that bite into the wood, eliminating the need to use a tool at the front.

ICBM · August 2014

A lot of people say bad things about WD40, but I've been using it as a "if contact cleaner fails" solution for decades and never had any problems with it, ever.

I wouldn't use it as a first choice, but if contact cleaner doesn't fix it your only other option is to change the pot, so you have nothing to lose by trying it.

It very often does work, too.

imalrightjack · August 2014

I have another question on this amp. It has been cleaned up and is crackle-free with a new speaker which sounds great. However, one of the valves in particular is rattling

If I touch it (carefully, obviously), it stops rattling. Does that mean the valve is going or is it the retaining thing that will be the problem? They hang upside down - is it wise to remove the retainers and just leave them?

Thoughts welcome!

ICBM · August 2014

Try removing the retaining clip and see if the rattle stops. If it doesn't, it's the valve!, they quite often do. It doesn't necessarily mean it's on the way out electrically.

Generally EL84s are quite a tight fit in the holder even without the retainer, and aren't heavy enough to easily work their way out, so if it proves to be the clip you can probably safely leave it off.

imalrightjack · August 2014

Cool. I'll try and pop it off. Easier said than done due to the position of the transformer!

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Repairing a Laney LC15R - help and advice needed

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