Smells like toast
I had just popped-in my Tung-Sol reissue 6550s. It was playing for a few minutes when I noticed that the tube distress indicator was lit (red plates). One of the tubes was running away. When I approached the amp, it smelled like burnt toast. I took it apart only to find one burnt cathode resistor. It's in parallel with a 5W 680 ohm resistor. I replaced it, but forgot which tube was doing it, so I ran it with the 340 ohm bias setting, which has 2 680 5W resistors in parallel. The bad tube did the same thing, slowly rose in current and started to approach the 63V limit of the cap. The cap tested good and looked fine, but now I'm thinking I should have replaced it. Oh well, we'll see what happens.
I put one of the other 6550s in and it works fine. Tube has some kind of internal short or alignment issue I guess. It worked fine at various points in the past and does play music, but likes it hot.
I had just popped-in my Tung-Sol reissue 6550s. It was playing for a few minutes when I noticed that the tube distress indicator was lit (red plates). One of the tubes was running away. When I approached the amp, it smelled like burnt toast. I took it apart only to find one burnt cathode resistor. It's in parallel with a 5W 680 ohm resistor. I replaced it, but forgot which tube was doing it, so I ran it with the 340 ohm bias setting, which has 2 680 5W resistors in parallel. The bad tube did the same thing, slowly rose in current and started to approach the 63V limit of the cap. The cap tested good and looked fine, but now I'm thinking I should have replaced it. Oh well, we'll see what happens.
I put one of the other 6550s in and it works fine. Tube has some kind of internal short or alignment issue I guess. It worked fine at various points in the past and does play music, but likes it hot.
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