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My Cary is a little over three years old (just went off warranty in the spring) and I am experiencing audio dropouts in both channels. It occurs while playing all sources. I checked the bias and found it to be spot on so I swapped out the Sophia Output tubes first and put back in the original low hour tubes from Cary and the problem persisted. I then swapped out the three 6SN7 tubes and the problem persisted.The dropout occurs at random times during a listening session. It sounds like a gradually fade out to near silence and then the sound gradually ramps back up to the original sound level. There are no clicks, pops, or static at any time. I have also noted the Power and Output transformers seem to be running cooler to the touch than I previously recall.
Any ideas out there? Could it be the power supply caps or coupling caps? Could my low hour Cary Tubes somehow be suspect; both channels drop out at the same time. If it is something simple I would first try a local shop but if the consensus is this could be more involved I would bite the bullet and ship it back to Cary and perhaps have things upgraded in the process.
Thanks,
John
Edits: 08/20/16Follow Ups:
Got the Cary fixed locally by Pat at Classic Tube Audio in Camas, WA. He replaced the Bridge Rectifier with a higher rated one and all is well again. Turnaround time was less than a week and in addition to the diagnosis and repair, he cleaned all switches and contacts, and tested and recorded the specs for two complete sets of tubes. All for a lower cost than shipping alone to and from Cary.
Highly recommended!
That was, hands down, the most unreliable piece of gear I ever owned! When back to Cary three times and still not right - hum, drop out, blah blah blah. I finally gave up and sold it - what a POS! Good luck on your problem. I'm sure I could have diagnosed it myself but did not want to void warranty as well.
I hope you made that clear in your description?
Ahhh busting ya balls!
I've found that it is unwise to put pen to paper as it were about items I've sold or was going to sell and then describe them some what differently.
I was burned years ago on an ebay sale that wasy. It was a piece I was trying to repair and get rid of a hum in the PS. I did make THAT clear in the description as well as the hum I couldn't get rid of. However the nut bag I was dealing with didn't want to hear that part. Only that the receiver had a hum - AS DESCRIBED!!!! But screw balls don't seem to really neede facts anyway. Just be careful.
I'm a little slow, just looked at a picture and you mentioned three 6SN7's. The 6SN7 in the middle will drive both channels, so be sure and wriggle that one in case it is a socket problem. And just saw the IEC power cord, make sure it hasn't half out of the socket (both ends).
Just to be clear for the OP
The driver tube is usually in the center and splitters on the outside.
I did mention that to him. It would be nice if it was a weak solder joint. He is out of warranty but will doing his own repairs cause any further problems with Cary's repair department $$ wise?
And the chop stick test isn't a bad idea. Just keep the speakers attached to maintain a load.
Sounds like a loose connection, check the easy stuff like the AC plug and fuse cap (if there is one). If the tube filament circuit provides filament power in series to any of the tubes, you could lose both channels due to a bad connection at a tube socket or even a tube, but it sounds like you substituted all of the tubes.
Try touching all of the above to see if you can recreate the problem at will. I wouldn't be too concerned about powering it up, tubes and associated circuits are not like solid state where a failed component tends to damage others.
The watch the tube glow suggestion was a good one, if it is something like power plug or fuse you should see the filaments go out and come back. Watching in the dark is good way to do this.
If it's both channels it's something in the power supply or some thing that can control BOTH channels, like a faulty switch.But my money is on something in the power supply. Does it have a rectifier tube? Do a visual check on the board and capacitors. Look for any physical changes.
Post your findings.
Charles
addendum I noticed it has a driver tube. Try changing that one. And also check it's components for changes.
Edits: 08/20/16
Thanks for the suggestions. I swapped out both 6SN7 driver tubes. As for a rectifier tube, I don't think so. From the Cary manual: "The power supply is a full wave center tap configuration running high voltage, high current fast switching diode rectifiers. The rectified 450 VDC is fed to a PI-L filter network."
As an electronic newbie, I am a bit nervous about opening it up. Based on the case, it looks like after removing the tubes, I have to flip it upside down to remove the bottom plate in order to inspect the innards? Is it okay to turn the transformers upside down?
when this happens and they measure good it could be something in the B+ power supply. Most likely the rectifier tube. Do you have a spare to try? If not, then you have to buy one to try to make sure.
Have you also tried calling Cary? Sometimes companies will honor warranties that are expired if it's not too far out from the expiration date. Won't hurt to try.
They are good folks to work with. Helped with with a tough trouble shoot and didn't milk me on the service issues.
I recently had a very positive experience with Cary service. Great service at a reasonable price.
Looked at the pictures. No rectifier tube so it looks like a component in the power supply is fading. I recommend he has it checked FAST before it blows and takes a bunch of stuff out with it.
The amp has solid state rectifiers, so something is going bad. I recommend not turning it on again until a technician or Cary looks at it.
Thanks for the advice on keeping it powered down. I am disconnecting the power cord. I sent an email to Cary and will follow up with a phone call on Monday to them.
John
John,
If you would like a local opinion, contact Pat Hickman @ Classic Tube Audio. He is in Camus, has a top notch lab and worth the trip if only just to see his setup.
Graham,
I shot Pat an email and he got back to me in a matter of minutes. I am going up to Camas on Friday.
John
Good call John, I think you will be glad you did.
Edits: 08/25/16
Graham,
Thanks for the lead in Camas. I think I will contact them and see what they have to say. I would prefer not to ship it across the country. I could also have them check out all of my tubes while they are at it.
Happy Listening,
John
I would be very interested what the cause was.
Cary's prompt response to my email inquiry:
"Most likely what is happening is your filament supply is failing. You'll have to measure and monitor the voltage for the 300B tubes over time to see if it falls off to zero. If it does then it is most likely the rectifier bridge that is failing and will have to be replaced. Let me know what you would like to do."
I will be taking it to Classic Tube Audio in Camas Washington this Friday; will post a followup once the repair is complete.
John
My moneys on failing solder joint in the PS
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