2. amps-preamps
  3. 119241-73122

Conrad Johnson CAV 50

Just acquired this beauty from my father in law. I've never owned a tube amp, so not sure if I should sell it, or keep it and pay him. Anyway, a question for you tube heads. One of the EL34 tubes in slot V7 ( a tube which can have it's bias adjusted, which I assume means the power transmitted) has it's red light constantly on. I turned the bias all the way down and it still flickers. However, I noticed that my left speaker sounded blown/distorted. When I turned the bias up, the distortion decreased. The instructions say to turn the bias down/counter clockwise, until the red light goes out. But, if I do this, it sounds bad. So, my question is this. Is it simply a tube I need to replace to fix that problem, and if I change one tube, should I change them all. Next question is I searched for the EL34 tubes and of course there are a large variety of them. Any thoughts. To me the amp sounds little bright with the Celstion SL6's I am using, so any warmer tubes would be nice. Also, if I were to sell this setup, any idea on what I might ask on pricing? Thanks.
Roly
rolyasm
jond's avatar
jond
5,794 posts
 
Roly you may also have another issue if it persists in both channels, perhaps a blown resistor or leaking capacitor, hopefully almarg or one of our more tech minded members will chime in with a better diagnosis. Or you can always simply call or email C-j on Monday. Either way good luck!
jond's avatar
jond
5,794 posts
 
Sorry that should read if it persists in that one channel after flipping power tubes. Perhaps an issue with the bias circuit even?
tls49's avatar
tls49
1,351 posts
 
I changed the power tubes (EL34) to the opposite sides and the problem persists.
Did the problem stay on V7 or did it move to the other side? If it stayed on V7, the amp may need to be looked at by a technician. If a tube cannot be biased properly, that should be corrected. Playing it long term will definitely not be good for the tube and if a defective part of the amp is causing the problem, that could affect other parts in the amp as well.

Even if the amp is working properly with new power tubes, it still won't be able to get maximum performance from the SL6. 

timo62
280 posts
 
Roly ,

It sounds like your left channel fuse protection has blown.

The fuse protector are located on each side of the amp between the far left and far right EL34 and the 6SN7 tubes. You will see there are "fuse out" indicators next to the fuse protection. If it is lit red then you have a blown fuse. You will need a Buss Fuse  BBS-3/4

If the fuse out light is red , power down the amp and just unscrew the black knob and the fuse will come out with the knob. This will also mean the one of your EL34 tubes have gone bad , so you will need to replace both left channel tubes , or you will keep blowing fuses.


rolyasm OP
14 posts
 
So switching out the tubes didn't change the red light which stayed on in the V7 position, regardless of the tube placement. There are not other red lights or "fuse out" indicator lights on. I think I read something on another forum about a "plate fuse", but I can't be sure that was what was mentioned and I can't find the thread again. 
I will give a call to CJ tomorrow. I'm sure it will cost a fortune just to ship that beast. I see some upgrades on their page, anything you recommend if I send it in. 
As far as the SL6's, I think I will list them on here or on Ebay. I have enough speakers and if I keep the amp I will want to take that money and use it on a speaker set that matches the amp better, or to help offset any repair costs. Thanks again for all your advice. 
R
More to discover