70's SVT question

[bobyoung]

My output VR3 won't balance,the tubes bias up nice and they're brand new Russian Tungsols. I can also only get about 15 V out rather than the 25 you're supposed to get. I've checked just about all the resistors and caps and everything seems good including the VR3 pot. I'm following the procedure correctly using a voltmeter across VR1 and VR2 with a 40 hz signal into a 4 ohm load, I just did my other head and it came out nice, 25 V out and balanced to 0V. With a voltmeter in the VR1 bias checkpoint to ground as the applied signal goes up so does the bias from 72 mv as it's supposed to, the other side VR2 stays right at 72 mv now matter how much signal that side gets which is obviously why it won't balance. I've checked most of the voltages and they seem in the ball park, so anyway I'm stumped for now anyway, any ideas Psycho? (or anyone else?)

[bobyoung]

Oh, the reason I say VR3 is alright is because from ground to R9 (I think, my schematic is fuzzy, anyway it's a 10K resistor) the pot goes from 15K to 0

[Psycho Bass Guy]

Try swapping out the 12BH7 drivers. The balance pot is only to get rid of hum and if it's reading that bad off and only on one side regardless of adjustment, hit the first active stage on that side.