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Repairs and/or modifications to C-J products

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Wildcat
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Repairs and/or modifications to C-J products

Post by Wildcat » Sun Nov 26, 2017 10:20 pm

As my signature shows, I have a Premier 11 on hand. I have had it for several months now and we get along nicely. It does not quite drive my Vandersteen 2CE as well as the Nelson Pass designed amp I had previously, but the Vandys are also not my long-range goal.

My dilemma, though. The 11 came with electrical tape on the power cord, likely a scuff in the jacket. I really would like to have an IEC jack installed so I can use one of my own power cables. In addition, I had thought of perhaps getting the amp upgraded to an 11A (which was a small modification to the bias circuitry to reduce noise).

As for issues, the amp has a very slight channel imbalance--on my PV14L, my two channel settings are three digits apart (such as 67/70 or 35/38). Not bothersome, but maybe I'm slightly OCD? :mrgreen: I also can hear that it is not as quiet as my previous amp--the noise is not quite audible from my seat, but I can definitely hear it a few feet away. I don't know if that is normal as I've never owned a high-end tube amp.

The amp has been retubed. KT120s, Brimar 6CG7/6FQ7, Tung Sol 5751. The channel imbalance and noise did not change when the tubes were replaced.

The cheapest option is to do nothing. ;)

I contacted C-J for information. An IEC jack is three (!) hours labor, plus parts and shipping, so about $400. They can't do the "A" upgrade any longer. No word on anything else, but the offer was made to install the Teflon caps for $1645, which is more than I paid for the amp. Needless to say, I won't be sending my amp in.

In general, is it wise to find a repair facility that can work on C-J components properly? I just don't want some self-proclaimed "engineer" to start talking about "improvements" by changing out all sorts of parts. I figure any bench electrician is not C-J and IMHO has no business tampering with their circuitry. Plus, I feel it's easier to resell an untouched C-J product than something that is tampered with.

I would like the "A" upgrade, but that would require schematics for both the 11 and 11A to find the differences, and I would hope that it would not require a whole new circuit board. (I would think it is just a change in existing components, or adding a couple.)

For the IEC jack, I could probably do that myself; a good jack probably costs $50-ish, and while I don't have a metal punch, I would probably have to work really slowly with a miniature metal cutting tool to make the proper opening. But if a shop could do it for an hour's labor (which is all it should take), I would probably pay it.

If anyone has a little input on repair shops, modifications, etc., I would appreciate it. The good, the bad, etc., and possible effects on the value of a modified unit. (Even my minor IEC jack install might seem like sacrilege!)
C-J PV-14L/C-J Premier 11/Vandersteen 2Ce

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Re: Repairs and/or modifications to C-J products

Post by admin » Sun Nov 26, 2017 10:34 pm

My two cents is that if you want to have the flexibility to change power cords, then an IEC plug placement is probably one of the easiest DIY projects. The hardest part is cutting the case for the plug but the plug border typically overlaps a little so if the cut is not perfect you will still be fine.

Doing a 11 to 11A upgrade is obviously much more involved and more things can go wrong. I believe we do have the schematics in our database so I would first take a look and see exactly what would be involved. Still might be very doable and obviously a small fraction of the price of having it "professionally done".
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Current Conrad Johnson Equipment in System: Evolution 2000, PV-12L, and D/A-2b.

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Re: Repairs and/or modifications to C-J products

Post by Wildcat » Sun Nov 26, 2017 11:00 pm

I think even someone in our local audio club has put an IEC jack into a chassis, so I may defer to their expertise if needed. (We have a few DIYers among us.) The chassis on this 11 is certainly thicker than others I have worked with in the past (mainly, project boxes from the electronics stores).

I don't see the 11 to 11A upgrade being as important, but it does make me wonder if the slight noise I am hearing is a result of that. If I remember the details, the noise came from the driver circuitry for the bias LEDs. And supposedly that same upgrade also made the LEDs a little less finicky. But it is not a deal breaker.

I am actually more concerned about the channel imbalance. It certainly hasn't gotten any worse, but I just hope it is not a future problem lurking there. That is why I'd worry about sending it off to be looked at--I would simply want it fixed, not have a lot of parts replaced due to an upgrade a technician feels "improves" the sound. Having never used a shop for high end repairs before, I don't know what to expect, should I go that route.
C-J PV-14L/C-J Premier 11/Vandersteen 2Ce

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