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major speaker (or OT) problems.
Some history first: Built 5F6A and tested it through _resistive_ 2 ohm load (actually an 8 ohm PA speaker with resistors is parallel). Amp worked fine. Bought a Weber cabinet and 4 Weber speaker$$ and spent the day today pulling what's left of my hair out.
The bloody amp won't output anything if more than one speaker is connected. It's supposed to handle 4 8-ohm speakers in parallel and I have the Mercury 2-ohm OT. But as soon as I connect the 2nd speaker, off goes the volume. Nothing. For a while I thought I had a short in the output jacks. Rewired them and same problem. I spent the whole day on this and my hand is permanently cramped from holding scope probes and DMM probes and soldering irons (just one) and pliers and screwdrivers and whatever else made my hand cramp up. It's so bad that I'm typing this note with a pencil between my teeth.
Anyway, could I possible have OT issues? Did my 2-ohm resistive load blow it up? How about running it without a load (only for a very brief time)? All voltages within 20% of schematic values. All signals are clean up to the output stage (20mV sine wave input resulting in 5v p-p on the output grids). But... no signal on the plates, just dc. Could it be too much nfb? I'm guessing, can't you tell. I'm also stumped and disappointed. I waited a long time for the day I could put it all together and jam away. Bummer.
Help (and beer) would be appreciated.
Larry
The bloody amp won't output anything if more than one speaker is connected. It's supposed to handle 4 8-ohm speakers in parallel and I have the Mercury 2-ohm OT. But as soon as I connect the 2nd speaker, off goes the volume. Nothing. For a while I thought I had a short in the output jacks. Rewired them and same problem. I spent the whole day on this and my hand is permanently cramped from holding scope probes and DMM probes and soldering irons (just one) and pliers and screwdrivers and whatever else made my hand cramp up. It's so bad that I'm typing this note with a pencil between my teeth.
Anyway, could I possible have OT issues? Did my 2-ohm resistive load blow it up? How about running it without a load (only for a very brief time)? All voltages within 20% of schematic values. All signals are clean up to the output stage (20mV sine wave input resulting in 5v p-p on the output grids). But... no signal on the plates, just dc. Could it be too much nfb? I'm guessing, can't you tell. I'm also stumped and disappointed. I waited a long time for the day I could put it all together and jam away. Bummer.
Help (and beer) would be appreciated.
Larry
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