Suspected Tube Out In PV11 Or Could It Be Another Culprit?

[Gregory Earl]

I was listening to my tuner last week and suddenly there was a weird kind of time warp distorted sound that started coming from both channels.I rushed over to my amp and turned it off. When I powered it up again I got distorted sound from both channels. Bad distortion. I tried different sources and got the same thing. I suspect a bad tube in the PV-11 since my amp is the solid-state Conrad Johnson MF-2200.

Thing is all the tubes in the pre-amp still glow. Am I wrong in thinking it's a tube? What should I look for here?

Thanks in advance for all replies.

[AnotherJohnson]

Glowing is not a sign of a good tube. Not glowing is a sure sign of a problem, but glowing by itself means nothing (unless it is the relentless glow of a runaway Power tube, in which case it’s a bad thing). Test the tubes, or replace them with known good ones if you can’t test them. Talk to CJ directly. I’ve never had bad advice from them.

[AnotherJohnson]

You might contact CJ directly. It may take a few days ( be patient), but my experience has been that CJ can be very helpful in chasing down problems. No one knows their gear better, and they have seen it all. They are patient, especially if you are not arrogant or pigheaded.

They have saved me countless hours of troubleshooting by steering me toward the most likely culprit.

[AnotherJohnson]

The other thing would be to take a look at the caps in either (both) units (amp and preamp). Any signs of leaking or discoloration or bulging, and that’s an obvious clue too.

A dirty volume pot could also be the culprit. It is even possible for transistors to fail with age and use.

So ... while tubes are an obvious and somewhat easy place to start, it is definitely possible for older solid state gear to fail too. Sadly I know this from nursing old solid state gear along through assorted refurbishments.

[roberto]

Hola Gregory,

I do believe that you have an open bias fuse...Check the fuses, that's why the sound is distorting. A bias voltage is not present, and this voltage is for all power tubes.

It is good advice from AJ to ask at Conrad Johnson an advice for this problem.

Happy listening!

[AnotherJohnson]

Something really cool from CJ about the PV 11 that I missed.

Circuit Upgrades
PV10 (including 10A and 10B), PV11, and PV12 preamplifiers can be upgraded to incorporate our latest enhanced triode (ET) – circuitry and can also be upgraded to include CJD Teflon capacitors.