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In Reply to: What would make one output tube go bright cherry red!! too much drama posted by henrybasstardo on November 30, 2006 at 22:09:27:
No problems with the RCA tubes. All sockets were cleaned. I guess the EH didn't like the 101C. Too cheap? There were supposedly a matched pair and I used them in a 500C with no issues. Is the tube bad now? It has a burn mark that looks like getter on the side of the glass. What is this? Guess it's time to invest in NOS outputs.Have a great weekend
Follow Ups:
He has talked about this before. I had another asylum guy that had problems like this in his Fisher. I had him go over his bias supply so many times he must have hated me. Jim set me on the right track and as far as I know the amp has been trouble free for years. Or at least he hasn't emailed me for anymore help and was satisfied enough to send me a fisher tuner as a gift:)Don't forget to change the coupling caps either as the grid leak resistor works with them to create a "filter".
I have to say I am not a fan of stringing the heaters under the cathode this way and injecting positive voltage to the grids. I'd get a transformer and build a DC supply and go with straight cathode bias. I'd hate to think what would happen if a small signal tube ever had an internal short. Besides the tube heater's cold resistance is way different than its hot resistance and they could very well inject some noise into the output tube's grids.
I would discard the tube. If you sent Jim your other tubes he could see if they match and maybe supply one tube that matched up with them.
"If you sent Jim your other tubes he could see if they match and maybe supply one tube that matched up with them"
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