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Hi folks, I recently purchased several tubes from a tube vendor for my McIntosh MC-30 amps and Cary preamp. For the MC-30's I got some NOS Sylvania 5U4 rectifiers and for the Cary some NOS JAN Sylvania 6SL7's and NOS GE 12AX7's for the separate phono stage. To make a long story short the 5U4's made some strange sounds in my amps and the 6SL7's when I installed them did not seem to work as I could not send any signal through the preamp into the speakers. On my right channel I could hear a slight slight slight signal but the volume control did not boost this signal through the speakers at all...in fact even when the volume was completely off, that slight signal was still there! The tubes do glow but they do not go! As soon as I replaced my original tubes, the preamp worked as usual. I guess my most important and immediate question at this point is this...in general if tubes are bad and you run them in the equipment for ten minutes or so like I did in my amps and my preamp, is there any damage to the equipment or is it designed so that a bad tube, like a bad light bulb, does not damage the thing it is plugged into? This is the most important thing to me. The next question is, supposing a bad tube can do damage, how do I verify that my equipment has not been hurt in some small way before that problem becomes bigger problems? Lastly, the tube vendor seems super reputable; when I told him about the 5U4's he immediately told me to send them back for some replacements so I am sure he will do the same with the other tubes but I am striking out here and wondering if going with some new svetlana stuff would be better than trying to track down good quality NOS tubes? As always, thanks for the advice. Shaun.
Follow Ups:
Try the tubes one type at a time. A bad rectifier will cause the amp to have no high voltage and, accordingly, no sound.
Steve, Hi, thank you for the response to my post. I really appreciate it. In fact, I read and appreciate a lot of the posts that you send through the list and I have learned a lot from you. You definitely have a heap of experience with equipment and I think it is incredibly cool of you to share your knowledge with the rest of us! You dont happen to sell tubes do you? Thanks, Shaun.
Shaun,Nope. Just like to restore old guitar amps. Kinda fell into it, by playing the crazy instrument. And finding that a lot of guitar nuts were getting not-so-great service on their precious equipment.
Hate to see a 1965 Black Face Fender Princeton get hacked to pieces with this gizmo and that add-on feature or some stupid latest and greatest speaker.
Kinda close to (but not the fine art) of luthiers restoring old Gibsons and Martin acoustic guitars.
My tube collection is basically, to resotre amps. But, I'd be happy to help you look for some particular stock.
quote: But, I'd be happy to help you look for some particular stock.QUOTE:
That's mighty generous of you Steve, does that go for all of us?
I'd sure like a line on a couple.
Mark,
McA,Seems you happened to get three DOA's. I'd have the dealer test the tubes (best in a working audio unit), before shipping them to you---to insure that the replacement set is good.
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