Laney Cub 12R Hot Transformer Solution

Laney Cub 12R Hot Transformer Solution

Laney Cub 12R diy mod

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I had some doubts about this little combo since I discovered the cab is made of compressed cardboard or some shit which was a shocker (read about it here). But I love the tones I’m getting out of it so I’m hanging in to improve the quality as much as I can. So after recovering the cab I added external voltage test points and drilled a hole directly above the bias trim pot so I can bias without pulling the chassis (I use a bias probe to read current). I made a wooden trim pot adjustment tool for it which works perfectly. It was at that time I noticed how hot the thing was getting. I read about the transformer heat issue some dudes were having but this was worse. The entire chassis was too hot to touch. I now have it running at 298 volts on the plate and biased at 22.3 mA which is pretty moderate so that left just the transformers as the heat source. I checked the temp on one of them and it was running at 120+ degrees F. The other one I just put my hand next to it and it was cookin too. After a little thought I had an idea. First I took some computer RAM heatsinks and used Arctic Alumina Thermal Adhesive and attached them to both transformers. I had some older Pentium processor 12v cooling fans with 1-5/8″ dia blades which turned out to be the perfect size. I attached one to each side of the rear cover and positioned them so each was pointed directly at a transformer. Wired them in parallel and made a switch box with a 12v power jack and hooked it all up. A 12v wall wart plugs into the switch box to complete the setup. These little fans move alot of air and they’re silent. So does it work? You bet your ass it does. The trannys are running at 85 F and

the chassis stays cool to the touch. That’s a hell of a reduction. It creates a flow that runs across the heat sinks, then exhausts out the unused 1/4″ jacks on the back side. The way the fans are situated some of the air deflects off the transformers and flows around the tubes to cool them down a bit as well. All in all the design just freakin’ works, on this amp at least. The only thing I’m still unsure of is just how hot are these transformers supposed to get normally. and am I just treating a symptom of a bigger problem. I’m still looking for that answer and I know it’s out there somewhere.
How hot do your transformers get? Leave an answer in the comments below. Click here to find out what these are made of!

UPDATE: Since I originally published this article I went back and changed the fans to some slightly smaller diameter 5 volt units because they don’t stick out the back side.

 

 

Russ

Gibson Les Paul Studio, Hamer Studio, Dean Soltero, Epiphone Les Paul (Korean), Ovation Celebrity, Blackstar HT-1R, Jet City JCA20H, Jet City JCA22H, Orange OR15, and a lot of dirt pedals, some store bought some DIY.

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