• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Question regarding value of Telefunken tubes.

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Last night I was testing some (hopefully final) xover mods to my HT column speakers (I will provide photos soon), and was using a Scott stereo integrated tube amp to drive them. However, the amp appeared to fail during testing (playing at a moderate average level with little or no apparent distortion even on peaks), so I shut down for the day. Since one output transformer had gotten quite hot and little but hum was coming out of the amp, I more or less assumed the transformer had failed for that channel (after all, the amp has to be around 50 years old).

This morning I powered the amp up again, and the problem was still there. I took a look at the 6BQ5/EL84 output tubes and saw that one was dark, so I turned the amp off again and pulled the tube. I was surprised to see that the tube had broken apart just above the socket and had no vacuum. Just to see if that was the only issue at hand, I powered the amp up briefly without the tube and played sound through it for a couple seconds. Both channels played, but the one with just the one tube was quite distorted of course. This gave me some confidence that the amp itself had survived the ordeal.

The actual tubes in the output were nearly new (probably around 100-200 hours) Telefunken 6BQ5/EL84's, of which I now have three. It occurred to me that it might make sense to put the remaining three up for sale and put some (admittedly lower quality) new manufacturer replacements in this amp. Does anybody have an idea how much nearly new gold pin Telefunken 6BQ5/EL84's might bring on Ebay, for instance?
 
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