Laney cub 12R head - broken. Help!

johnboyno8

I've got a Laney cub 12R head which was fine for about a 2/3 years of use. Used for a lot of practices and the odd gig when the venue was very small. Great amp which I love!

I bought the amp second hand, Reverb never worked since I bought the amp. This didn't worry me as I didn't feel I needed it tbh having a decent pedalboard anyway.

Then a couple of months ago whilst practicing my guitar kept cutting out. It would not completely die, just lose a lot of volume and sound very muddy and distorted. For a while I thought it was a doggy patch cable on the board and usually if I stopped playing for a minute and fiddled with the leads, all would come back on. However after fitting all new patch cables, it persisted and gradually got worse. Now it's unplayable.

I put some new JJ valves in as they wanted changing anyway, but it hasn't made any difference. 

There is quite a bit of information on various forums about this yellow thermal fuse which apparently is a very common problem on these older cub amps...??
 Some people say the fuse isn't even necessary and have just removed it!? I have no idea - this is only what I have read.

Does anyone have any experience with fixing these? Also why the reverb might not work?  I know the amp is only a cheap amp, but it's so handy and I used it a lot. But if it's going to be expensive to repair, I'm not sure whether it's worth it.

I'm in Chippenham, Wiltshire, if anyone is nearby who would be willing to repair it for me. I have the schematic.

Thanks,

John

ICBM

It is very likely to be the thermistor - that's a good description of the symptoms. Although it's a bit odd if it seemed to be related to your pedalboard...

If it is the amp, it is probably safe to bypass (not just remove, or the amp won't work at all) the thermistor. I tested one with it done and it seemed to run fine, and not do anything it shouldn't - however, it's there for a reason, which is to protect the slightly underspec power transformer from overheating and cooking itself if you get a set of valves with unusually high filament current draw, so do this at your own risk.

The reverb fault could easily be a bad contact in one of the jumper connectors to it - I've come across this a couple of times in these. I cut the connectors off and solder the wires directly to the board.

Grumpyrocker

I had to send my Cub 12R to Laney to fix the thermister under warranty. This was about four years ago. Since then the amp has worked fine. 

DJH83004

To be honest, I have lost count of the number I have swapped out and put 20mm fuse holders and fuses as replacements on this generation of Laney amps. But not reverb related, so you will def need your local amp tech to investigate. 

Voxman

I have the 12R combo. And like yours, it was sent back to Laney to fix the thermal fuse issue after 3 months but has been fine ever since. The symptoms however were complete cut off until the amp cooled, not worse tone, volume drop or distortion ( but keep reading).

However, about 12 months later the amp lost volume and became distorted.  Checked the tubes, which were perfect.  Returned the amp under warranty, and it was fixed and has been perfect ever since.  (They also replaced a flickering power light with a much better unit). The problem was a loose valve seat connection and burnt out valve seat housing under one of the power tubes.  So you might want to check the valve holders and connections in your cub.

Prior to the repair the digital reverb was horrible - very wishy washy and I didn't like it. Since the repair, the digital reverb has sounded excellent..completely different.  I can't explain this because its a digital not valve driven reverb...perhaps they found something else when they had it but maybe the circuit is affected by the power to the valves in some way.