Supro 24 With One Power Tube Not Working
Posted: Sun 10/22/17 9:28 pm
Hi Forum,
I build this Supro 24 a while ago. I recently picked it up at the store that was selling it. I've got only one of the 6972 power tubes showing a glow. I checked voltages and I'm measuring very high voltages into the preamp section. About 350V DC. this is almost double what should be in the preamp section for the three 12AX7 tubes. The heater voltages measure 3.5 V AC and I do get voltage on the Output Transformer going to the two 6972 power tubes. The amp hums but doesn't do anything. It was running fine after startup for several months. I tried changing out the power tubes and they performed the same. Only one tube was showing a glow.
Could I have a blown Output Transformer??
Is there something else I should look for??
Thanks
Rags
I build this Supro 24 a while ago. I recently picked it up at the store that was selling it. I've got only one of the 6972 power tubes showing a glow. I checked voltages and I'm measuring very high voltages into the preamp section. About 350V DC. this is almost double what should be in the preamp section for the three 12AX7 tubes. The heater voltages measure 3.5 V AC and I do get voltage on the Output Transformer going to the two 6972 power tubes. The amp hums but doesn't do anything. It was running fine after startup for several months. I tried changing out the power tubes and they performed the same. Only one tube was showing a glow.
Could I have a blown Output Transformer??
Is there something else I should look for??
Thanks
Rags