Yeah, that would do it.
Many get confused about the (+) supply terminal being grounded, but that's necessary to have a negative output voltage.
Ok, are the red, red, and red/yellow wireds still taped off?
Don't reconnect those until this is resolved.
Let's hope that shorting the bias HV tap to ground didn't ruin the power transformer. We'll see.
Many get confused about the (+) supply terminal being grounded, but that's necessary to have a negative output voltage.
Ok, are the red, red, and red/yellow wireds still taped off?
Don't reconnect those until this is resolved.
Let's hope that shorting the bias HV tap to ground didn't ruin the power transformer. We'll see.
Yes, the 4 wires that go to the rectifier (red, red, yellow, yellow) still taped off, the gnd taps, yel/red, yel/red are grounded.
I will fix this idiotic mistake and then try again with red and yellow off
I will fix this idiotic mistake and then try again with red and yellow off
The first mistake is free.
It's only idiotic if you do it twice.
So triple check all polarities, wiring, and connections.
It's only idiotic if you do it twice.
So triple check all polarities, wiring, and connections.
Haha yep 🙂
Okay back in business, just connect all 4 to the rectifier or one at a time again to be safe?
Okay back in business, just connect all 4 to the rectifier or one at a time again to be safe?
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You pretty much have to connect them all at once. Good luck, and keep using the Variac until it's proven.
First turn the bias pots to minimum tube current ( maximum negative DC voltage).
Then before inserting any tubes, check out the bias circuit operation.
The pot wipers should go from roughly -20V to -50V (to ground) when pot is rotated.
Make sure the DC bias voltage is negative.
Leave pots set at -50V so tube currents will be at a minimum when amp is turned on.
Then adjust both bias pots for proper tube currents. They will interact somewhat.
Recheck after 30 minutes or so.
First turn the bias pots to minimum tube current ( maximum negative DC voltage).
Then before inserting any tubes, check out the bias circuit operation.
The pot wipers should go from roughly -20V to -50V (to ground) when pot is rotated.
Make sure the DC bias voltage is negative.
Leave pots set at -50V so tube currents will be at a minimum when amp is turned on.
Then adjust both bias pots for proper tube currents. They will interact somewhat.
Recheck after 30 minutes or so.
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LOL. I've done that, popped in an eyelet strip and forgotten that one eyelet is grounded to the chassis. Glad you got it resolved. Like you, I had to look at the photo twice. ;-)