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Yesterday I started up the DIY Tube ST70, I began using some old Sovtek EL34 tubes..everything went fine, bias was established and steady with no trouble. Disconnected the amp from dummy loads etc and put it into my system. Right channel output way too small, also may have been some tonal differences. Turned of the amp pulled the Sovtek tubes and installed a practically new set of EH 6CA7's, was able to set the bias with no problems. Re installed the amp in the system, turned it on and there was no change to right channel output still way too weak.
This amp has 2 Dynaco cloth lead output transformers that were obtained at the bay. I am wondering if the symptoms I have described are a bad output transformer. Or could the problem be on the driver boards..
Thanks

The first thing I would check is tat all the components in the right channel are in the correct spots , and that you didn't get a couple resistor in the wrong location . Also that the resistors are the correct value and not marked wrong . The sub the input tubes from side to side .

Could you take the voltages from page 9 of the manual and post them here?

Shannon

OK yes I will check the voltages and post them, might not be till tomorrow though
Thanks

OK I have taken all the voltages, there are some pretty big variations from the listed values. I have put the listed values in parens next to each measured value..

Voltages:
Cap: A=311.6 (300) B= 360.6 (350) C= 442 (425) D= 458 (438)

V4-V7

1= .523 .520 .52 .52 (.5 V)
2= 3.58 3.57 2.98 2.98 (6.3VAC)
3= 437 438 438 438 (418)
4= 442 443 443 442 (421)
5 & 6= -39 -39 -39.5 -39.5 (-35)
7= 2.96 2.95 3.56 3.57 (6.3VAC)
8= .51 .51 .51 .51 (.5)

12AX7 ( I am only noting the pins that measure incrrect values)
1= 201 (190V)
4= 3.55 (6.3)
5= 3.56 (6.3)
6= 201 (190)
9= 2.94 (6.3)

V2 and V3
1= 259.8 255.5 (245)
2= seemed to fluctuate between -1mV and +2/3mV
4= 3.58 2.97 (6.3)
5= 3.57 2.97 (6.3)
6= 252 258.8 (245)
7= behaved the same as pin 2
8= 13.5 12.9 (13)
9= 2.95 3.57 (6.3)

V8 5AR4
1= 11.7 (0)
2= 458 (438)
3= .01 (0)
4= 236 (366)
6= 244 (366)
8= 458 (438)

J1= -39 (-35), J2= -39 (-35), J4= 2.96 (6.3), J5= 3.55 (6.3), J6= -42 (-37)
J15= 2.97 (6.3), J16= 3.57 (6.3), J19= 312.6 (300), J20= 362 (350)
J21= -42.5 (-37), J22= -39.4 (-35), J23= -39.4 (-35)

Moved to this thread:
viewtopic.php?f=6&t=6112

Shannon