single ended 6BQ5 amp, heater for the two 12ax7a preamp tubes is dc,
customer complained vol was dropping out,
these engineers nowadays do not know anything about tubes, just Class D powered monitors that sound like crap because they no hear nuthin but $$
so what do they do? they try to heat tubes with 1N4007 diodes, can you believe it?
sure, they last for a while, until the cold cranking amps of the tubes gradually melt them away,
the ammeter was jumping up and down when powering the 6.3 circuit from an external variac set at 6.something,
all the diodes were pulled and tested good on the dmm checker, but guess what, they were bad, failing under load in a weird way, seen this before but not often,
this is something which will drive most people nuts and have them with an intermittent amp on their bench for 2 weeks,
so we did some thinking and decided to go with brute force.
get rid of the diodes and build an off board heavy duty bridge circuit with some 3 amp 1000 volt jobs that happen to come in yesterday from hoffman or mojo, i don't know, i think i have long term covid brain fog even after getting jabbed 4 times like a pincussion voodoo doll but that is another story,
leads from the diodes make good heat sinks unlike flush mounted diodes on a circuit board, diodes on the far right,
bottom line is we ran some wires directly to the tube sockets to avoid wimpy trace failure syndrome (WTF-Syndrome) to our new bridge and no more 2 amp needle jumps on our varaic in fact the whole amp works so we are in fat city....over.....
you didn't say over........ over......
customer complained vol was dropping out,
these engineers nowadays do not know anything about tubes, just Class D powered monitors that sound like crap because they no hear nuthin but $$
so what do they do? they try to heat tubes with 1N4007 diodes, can you believe it?
sure, they last for a while, until the cold cranking amps of the tubes gradually melt them away,
the ammeter was jumping up and down when powering the 6.3 circuit from an external variac set at 6.something,
all the diodes were pulled and tested good on the dmm checker, but guess what, they were bad, failing under load in a weird way, seen this before but not often,
this is something which will drive most people nuts and have them with an intermittent amp on their bench for 2 weeks,
so we did some thinking and decided to go with brute force.
get rid of the diodes and build an off board heavy duty bridge circuit with some 3 amp 1000 volt jobs that happen to come in yesterday from hoffman or mojo, i don't know, i think i have long term covid brain fog even after getting jabbed 4 times like a pincussion voodoo doll but that is another story,
leads from the diodes make good heat sinks unlike flush mounted diodes on a circuit board, diodes on the far right,
bottom line is we ran some wires directly to the tube sockets to avoid wimpy trace failure syndrome (WTF-Syndrome) to our new bridge and no more 2 amp needle jumps on our varaic in fact the whole amp works so we are in fat city....over.....
you didn't say over........ over......
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