845 socket fault on CAD-211AE

[Amfibius]

I thought I would post this email I sent to Cary as a FYI. Any of you guys with this spring type tube socket should make sure it is NOT bent and does NOT come into contact with the metal sleeve of your valve ... otherwise expensive headaches will ensue!!

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Dear tech support,

I am writing to let you know of a problem with the 845 socket on the CAD-211 Anniversary Edition. I have owned my CAD-211AE's for 5 years, bought new from my distributor in Melbourne.

The problems started when I tried installing another valve in my amplifier. The valve was quite tight and difficult to remove. As you can see from the included picture, the terminal was inadvertently bent upwards when I tried to remove the tube - although I did not know this at the time.

Over the next few months, I suffered a series of expensive tube failures. It was always the same socket that was killing the tube, and it has been returned for repair a number of times. Some of these failures have been spectacular - on one occasion it took out the bias pot and a resistor. On a couple of occasions, the fuse literally exploded with fragments of glass in the fuse socket!

What really threw me was the intermittent nature of these failures - the tubes would fail with no rhyme nor reason, even when I didn't touch the amp. At first I thought I had bought faulty tubes, but after the 3rd tube died I started to smell a rat.

I have included a picture of the suspected problem. The terminal comes very close to touching the metal sleeve of the 845 (arrowed). I have also drawn a diagram to illustrate the problem.

My technician suggested changing the sockets on the amp, which I did. He showed me the design of the new socket - the area at risk of touching the tube has a rebate on it that reduces the risk of a short.

I am providing this information FYI only to help you improve your product. I otherwise remain a satisfied customer and am very happy with all my Cary products.

Kind regards,

Keith



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[jdandy]

Keith.......That was a respectful and kind letter to Cary. Nice catch on the manufacturing defect, too. Way to go.

[Dj_AmTraX]

I have the 805ae. You think I may have the same issue? I have sent one amp in for repairs before. I have new tubes but have not used the amp in over a year.

[Amfibius]

Thank you Dan ... I have found that there is never any need to be disrespectful to anyone. All I need to do is state the facts and any implied displeasure is usually enough And it wasn't me who caught it ... it was my tech.

Mike I used to have the 805AE and I know it had the same socket as the one installed in my 211AE. I don't know if you have the same issue. I can tell you that I have four of these sockets, and only ONE of them was killing tubes on a regular basis. What kind of repair was needed for your amp?

BTW, my tech did warn me against changing tubes too soon after turning the amp off. To illustrate, he clipped his multimeter on the valve - it indicated 900V. He then turned the amp off, and it took a good 10 minutes for the voltage to drop down to zero! He said that this design does not have a bleed resistor (I think that's what he said, i'm no tech!) - sounds better, but dangerous if you try to swap 845's before the caps are discharged. And, as shown - it does not take much to short out the tube if you try to move it while the caps are still charged.

[Dj_AmTraX]

I don't know what caused my 805 to smoke, but it took out a few parts and needed to go back to the mothership for repairs. I learned not to "hot swap" the tubes after my McIntosh Mc2000 fried.

Maybe i'm dumb, but I really don't understand how your socket got bent? What should I inspect before I put my 805 back into action?

[Amfibius]

Hi Mike, the socket got bent because some 845 tubes have fatter bases than others. The Shuguang 845B has a particularly fat base - when I inserted it, I managed to get it in ... but I had trouble getting it out! Presumably the locating pin (or something) snagged on the terminal, yanking it up when I pulled the valve out.

Before you mount the 845, take a good look at the terminals in the socket and make sure none of them are pointing upwards. All should be perfectly horizontal. When the tube slides in, it should engage easily.

I received this very prompt reply from Cary:

Hello Keith.

This is incredible. We've never seen anything like this but would like
to know more about this socket your tech installed. Could you let me
know what this socket is?

Is it possible on your 845 tube that the metal guide pin broke off and
the tube twisted further then it should? I'm sorry that you've had this
experience and we are always looking for ways to improve our designs and
so if there is a socket that would protect the tubes better we would
love to know.

I'm glad things are working well again. These are wonderful amplifier
and we want you to have many more years of enjoyment from them!

Have a great day!

[Dj_AmTraX]

Thanks for the tips. I'll be sure to check it before I put it back in action. My tubes are all factory stock. I don't know who makes the 211 & 845 & 300b. Do you know?

[Amfibius]

I don't know ... mine just says "made in China". I can tell you that it does not look like the Shuguang 845B which I have. If it's not Shuguang, then it's one of the others ... and only a handful of manufacturers in China make 845's ...

[Dj_AmTraX]

How does the 211 compares to your old 805? Is it a huge upgrade? The 211 is very pretty. Some pictures please?

I have a SLP-98L in the closet that I would like to use someday.