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CJ PV-10 no sound

I installed a couple of GE 12AT7WA's (bp triple mica, aquired on E-Bay)into my CJ PV-10 today, and as soon as it came on, snapping sound and a hum. Now, no sound coming from pre-amp. It appeard as if one of the tubes shined brighter than it ought to prior to this happening. I'm going to go and get a new fuse to rule that out, but it looks OK. (BTW, so much for a the tube tester. Tested very good, no shorts!). On a seperate note, if I'm not able to get it fixed right away, I've tried running my NAK 670zx directly to my Classe 15 amp, and running my X-Ray CD player through the cassette deck. Sounds great (although I ALWAYS miss my tube sound). Any problem with this? Thanks
countryjazz2
countryjazz2 OP
17 posts
 
I tried switching out the tubes. I'm getting a pop when the preamp would usually kick in (similar to the one you get if you shut the preamp off while the amp is still on? All the tubes test OK, including the ones that I put in that appeared to blow it out.
mofimadness's avatar
mofimadness
4,982 posts
 
If you are getting a "pop" instead of a "click", that might be the mute relay. When you turn the preamp on, the mute relay stays on for the first 30 seconds or so to stabilize the electronics and tubes. Then it clicks off to allow the signal to flow through.

I was a cj dealer back in day and we had alot of problems with faulty mute relays. I'm not sure how old your preamp is, but I'd give a call the cj tech support and see what they have to say.
orpheus10
8,668 posts
 
If you have a shorted capacitor some where, it will blow the tube each time it's replaced. That can get expensive. I think you should send it back to CJ.
countryjazz2 OP
17 posts
 
It sounds a little like when you accidentally shut the pre-amp off when the amp is still on, but not as bad. No sound in the speakers whatsoever after that.
microstrip
180 posts
 
I would also suggest a power supply fault - the PV10 has a series pass HV regulator using an MJ340 , a MPSU10 and a MPSU60 transistors. Most probably the fault will be in first two transistors - the third one is just a current source to bias the zener diodes used as regulators.

As they are inexpensive I would risk replacing them if there is no HV at all at some parts of the tube sockets.

I have owned several cj preamplfiers and amplifiers for a long time and the few problems caused by defective tube problems were always solved replacing just these three transistors.
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