Problems with a Laney Cub 10
Hi. A couple of months ago I bought a Laney Cub 10 amplifier that I found in a store as a demo model. It worked great for daily use until last Friday when I took it to band practice. When I got home it turned on fine, I let it warm up a bit and then started playing. It started ok and then the volume started to drop to nothing and the power light went out and there was no more sound. Prior to this the power light did tend to go out while playing, but the amp would stay on. The amp didn't receive any hard knocks. I opened it up and looked at the tubes. I took them out and reseated them. The amp stayed on fine for 45 minutes without being played. I thought I had solved the problem, but once I start playing throught the amp it loses power and goes out again. After it sits for a few minutes it will turn on again, but the problem will repeat itself.
I live in Indonesia and in my area there aren't really any amplifier service shops, so I'm going to try and deal with this on my own. Does anyone have any thoughts on what might be going wrong?
Thanks for writing. Well, that might be a tough one! Many vintage amps use a pilot light that runs on low-voltage (filament) voltage rather than AC wall voltage. On this type of amp the pilot light can go out but the amp will still work, but I'm not certain if the Laney uses this type of light. In your case, about all you could do without learning to read voltages is to replace the tubes. I'm actually stumped about why the amp works for a while and then dies. If you dare, take a hard look inside the amp chassis and look for some kind of loose connection. Sorry to be so unhelpful, but this is a tough thing to troubleshoot without seeing the amp but it could be a good excuse to learn more about how tube amps actually work if that sounds interesting to you.
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Hi Skip,
Thanks for getting back to me. You are right about the Laney using a pilot light, it's 6 volts. Right after you got back to me I opened up the amp and started checking the connectors. I found one that was slightly loose, but didn't seem too bad. I snugged it up against the circuit board and then started playing through the amp with the chassis still out on the bench. It worked, but it seemed like the fix was too easy so I kept playing it like that expecting to eventually notice something else. After playing for a few days I put it all back together, and it still works. I waited until today to write back because I didn't want to declare victory too early, but it seems that it worked. Thanks for the suggestion. I've been enjoying your 'The truth about vintage amps' podcast, so thanks for that too.
Have a great day,
Greg McGuire
Hi,
Well the problem with my amplifier working fine for a while and then shutting down is back. I have found that I can lengthen the amount of time before it quits by using a fan to draw heat away from the back. This way it dies after about 40 minutes instead of 20, but eventually it shuts down no matter what I do. After it dies and I turn it off, I can flick it back on and it works after just a minute or 2. The longer I wait with it turned of it seems, the longer it will last before it shuts down again. If anyone wants to take a look at the schematic you can find it here. https://elektrotanya.com/laney_cub-10_sch.pdf/download.html. There aren't any amp techs in my areas. Does anyone think I might be able to solve this by changing out some tubes or something like that?
Any advice would be great.
Tonight I tried the amp again with my guitar. I started with the volume on the guitar at full and the amp at 2.5. I played for 9 minutes and had no problems. I turned it up to 3.5 and played for another 9 minutes, again no problem. I turned it up to 4.5 and played for 3 minutes and then the amp volume died and the power light went off. Maybe that extra bit of info might give someone out there some clues.
Thanks for reading and have a great day.