Laney LC15 Volume Fluctuation, Suspect Pots

[smazgard]

Hello I am Tim and I am an experimental guitarist from Manchester, UK. I have recently bought a used Laney LC15 which I love for its sound, but is not working reliably. Was wondering if you people could help me with advice on repairs and spares?

The problem is that the volume abruptly goes down, or cuts out completely. This can happen at any time but usually occurs when unplugging and reconnecting the guitar, or when plugging other amps in to the mains.

The volume usually comes back on if you fiddle with the 'Gain' knob, This led me to suspect that the pot is corroded or dirty. I partly dismantled the amp and sprayed Switch Cleaner and then Lubricant onto the Gain pot. That seemed to improve things, but the problem still occurs. I have recently noticed a similar issue happening with the Bass pot as well.

So the questions Id like to ask are:
1) Could this actually be a valve problem not the pots?
2) Where to get replacement pots for this amp?
3) How to get the plastic knobs off the pots without damaging them?

Hope somebody out there can help. Thank you.

Tim

[Mars Amp Repair]

hello Tim,
I'd first check the solder connections to the board (if they are soldered to a board). One way to easily determine if it's a bad connection on the pot is to remove the retaining nut & slightly wiggle the shaft from side to side. This in effect wiggles the actual pot on the board. You can tell if this is your cause, or at least if your close to a bad connection.

If it still seems to be the pots, many of the pots now adays are beginning to show up with loose crimp connections from their leads to the actual carbon tracks on the phenolic in the pot. I'm thinking if your issue is not merely bad connections on the board, this may be the case.
You can remove the pots & VERRRRY carefully recrimp these rivet points, but it is very easy to over do it & crack the phenolic.
As for replacements that depends on a lot of parameters. the basic value of the pot ie: resistance & taper...also the physical characteristics can be one of the most difficult facet to match up.
I am warranty authorized to Laney here in the states & I believe if you contact them, they will be easy to deal with to procure parts. glen

[Enzo]

Before you open it up, if the amp has either an effects loop, or a pair of jacks marked preamp out and power amp in, take a spare cord and plih it onto the effects send, and the other end right back into the effects return - a sort of external bypass if you like. If this restores the sound, the return jack needs service. The same test on the preamp out/power amp in pair of jacks - if there. Loop jacks are a very common problem.

And for that matter, ball up your fist and whack the top of the amp smartly. Turn the reverb down for this to avoid loud reverb noises. Does this have any effect on the sound levels? It should not, but if it does, it means a loose conncetion somewhere.

I fear when you turn the controls you suspect, that the little vibration it makes is conducted to teh circuit board, and irritates the loose connections.

[smazgard]

Thanks

Thank you for your replies to my post. I have now taken the amp apart and cleaned and oiled the pots again. Its improved but still cuts out occasionally. Whacking it does fix it when it cuts out, and so does pressing the gain pot in gently without moving it.

The pots Ive cleaned now feel different when you turn them. I think there was perhaps some grease on them which Ive cleaned off?

Still cant get the plastic ends off the pots. I am afraid to pull too hard in case I break something! This is now the only thing preventing me from getting at the pots with a soldering iron.

Anybody know if Laney apply grease to these pots, and if there is any special trick to removing the plastic knobs?

Thanks

Tim

[Mars Amp Repair]

I don't think Laney has any special 'grease' on the pot shafts. There are some knobs out there that are held on by a compression nut that is hidden under a cap on the end of the knobs. Trace Elliot used them.

Other than that, sometimes you'll get some chump who actually will glue the knobs on because they've become loose. Not much you can do in that case. I've actually pulled the pot shaft out of the pot as there was no other way to get the knob off.

I suppose if you were certain, you could chop the knob up to get to the nut. Either way you're going to have to replace something.

glen

[Prairie Dawg]

hello Tim,
I'd first check the solder connections to the board (if they are soldered to a board). One way to easily determine if it's a bad connection on the pot is to remove the retaining nut & slightly wiggle the shaft from side to side. This in effect wiggles the actual pot on the board. You can tell if this is your cause, or at least if your close to a bad connection.

If it still seems to be the pots, many of the pots now adays are beginning to show up with loose crimp connections from their leads to the actual carbon tracks on the phenolic in the pot. I'm thinking if your issue is not merely bad connections on the board, this may be the case.
You can remove the pots & VERRRRY carefully recrimp these rivet points, but it is very easy to over do it & crack the phenolic.
As for replacements that depends on a lot of parameters. the basic value of the pot ie: resistance & taper...also the physical characteristics can be one of the most difficult facet to match up.
I am warranty authorized to Laney here in the states & I believe if you contact them, they will be easy to deal with to procure parts. glen

I have one that came in today for a similar problem. Is this fairly common among these, and does the advice hold true?

Thanks in advance