Conrad Johnson LP66s Problems

Okay, the amp is back from Conrad Johnson and running beautifully. 

Talked with, I believe it was, Keith, who advised that I was using small tubes with too low a voltage. Not sure how to explain how this happened except to say operator error while tracking down the problem before sending it in to CJ. I think I had a bad 6922 tube and when I tried a replacement set I screwed up due to grabbing the wrong European version. Stupid me. 

Anyway, new Golden Lion 6992's and EH 6550 power tubes; and order is restored in my universe.

I have replaced all the power and driver tubes and confirmed that they are not the problem.

Jeff at CJ said to send it in and they wll look at it.

What Jeff said is exactly what I would recommend. Audiophile equipment needs to be treated by experts and the behavior you are getting is not normal.

Jeff is giving you an honest answer. That is how he works. He could guess what is wrong but that would not help you. He needs to put the amp on the bench and determine what is wrong. It could be anything from a simple diode to something in the power supply. It is a good amp. If you want to keep it, it is best to send it in. Happy to have a call with you.

dsper

Being a 2nd owner (at least) it is certainly time for a Tune-Up (no pun).

Keep us posted on your experience with Jeff at CJ.

Happy Listening!

Hi, 

For anyone who might be wondering, Jeff at CJ responded to me by saying my LP:66S needs to come in for repair if i have inserted new tubes and the problem still happens...

Did not comment on what could be wrong and what it might cost...

Leaves me so warm and fuzzy...

Dsper

@celloover, dsper, I spoke with the factory today. Jeff asked that you use the website "contact" and send a message and he will get back to you.

Thank you for that!

I installed anew set of EH 6550 power tubes today and the amp is still doing the same thing. The sound stops on the right channel and then there is a thump and then a buzz as the power comes bac. Doers this every few minutes..

I will contact Jeff and see what happens. 

I appreciate everyone's interest and suggestions.

Thanks for listening,

Dsper

@dsper 

I start it playing. Occasionally, one channel will go out and then come back on with a thump. A while later, it will do this again

I know you are discussing an amp, but I recently had this exact problem with my tube preamp, especially the awful thump.  Like you, put in new tubes and same thing happened.  Was about to send my unit for repair when I decided to ask the distributer if there was a repair facility they recommend.

The distributer said before sending it in that the problem may be caused by a loose tube pin socket and there are two ways to check this; One is to gently pinch the socket sleeve using small pliers to make the pin contact tighter.  The second is also quite effective but easier to do. Simply bend each tube pin slightly inward and outward for better contact with tube pins slightly bent in opposite direction. The point is to create more tension inside the socket holes for a firmer grip.

I couldn't believe it worked like a charm. Used the second method which took all of minute.

As a side note, it is remarkable how much more robust my old school preamp tubes including Telefunken, RCA and GE are built compared to newer Psvane tubes, especially the pins.  I was not careful and one of the Psvane pins broke off, no chance of it happening with the NOS tubes.

dsper

keep us posted on your CJ repair experience.

Happy Listening!

dsper, I spoke with the factory today. Jeff asked that you use the website "contact" and send a message and he will get back to you.

Your amp is very sick fix it ASAP!!

The bias light may flash as you bias the other tubes. Just bias them once a s if needed adjust.

Yes, you can use different brand tubes. Just bias them the same way.

Sounds like it may be more than just a bad tube, ESPECIALLY when you say three different sets of tubes exhibit the same problematic behavior.

I had an Image 65i (with 6550 outputs) a few years back in which, when one tube went bad, took out the bias resistor in the circuit. When I took the unit apart, you could tell the resistor had been fried.  I had to hunt down a replacement and do a bit of soldering to replace the burnt one.  That fixed the problem and everything ran fine afterwards.

Also, on a push-pull tube amp, there are two tubes per channel. Adjusting the bias of one can affect the bias of its mate, so it often takes two or three passes to get both to the right bias level.

Yes you can mix with no harm.

@cellorover Is it the fuse light that is coming on?

No, not the fuses. There is red bias light for each power tube. If the bias is wrong for a tube, the red light will go on. Each power tube has its own light and you are to adjust each tube by turning the screw so that the red light goes on and then turn it back until it is just off.

That is why I am asking about whether you can mix 6550 tubes from two manufacturers so that i have spare tube to rotate through to find a bad one. 

Thanks for the kind offer of support.

Dsper

I keep adjusting each tube and eventually this stops

Keep adjusting until all is well.

I have started trying to rotate tubes and it seems I can move this problem from the right to left channel,

It sounds like a bad tube to me. Buy some new ones from Upscale or CJ. 

Is it the fuse light that is coming on? Check the fuses. What you are describing maybe a bad diode. Call CJ and ask for Jeff. I provide concierge service for CJ, so I am happy to help anyway I can.