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In Reply to: RE: another pic posted by frankford on March 05, 2012 at 17:22:57
It's hard to tell from the pictures.You said "I went back and wired the heaters per schematic, high side to .68 ohms to pin 7 of one tube. I wired from pin 7 to other .68 ohm and left the resister to pin 2 of other 6550."
This is a little confusing. forget about pin 2 and pin 7 being swapped. You can swap them or not.
The bottom line is, one filament of one 6550 should be connected to the filament winding through a .68 ohm resistor. The other filament of the other 6550 should also be connected to the filament winding through a .68 ohm resistor with nothing in series.
pay no attention to the type of tube in the drawing. That's the only tube symbol of a tube that showed the heater connections I could find.
If it doesn't work with one side grounded then you have a shorted (to ground) heater winding.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/05/12Follow Ups:
I had it wired up this morning the way you are showing. I was getting 3.35 across the heaters. This was the reason I wanted to lift ground. The amp oscillated with this method.
You have a shorted heater (filament) winding.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I just shut down the amp and the channel that wasn't' working came on for a second. Would this also fall in line with a shorted winding?
I have no idea about that. That could be a separate problem.
The heater winding just powers the heaters in the tubes.
You said you got only 3.3vac hooked up the right way?
Try it without the resistors and measure what you get.
I really do think there is a problem with the heater winding of the power transformer.
BTW In a in-directly heated tube, like the 6550, they are called heaters, not filaments. We all say filaments even when we know better.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
took the resister off of one of the heaters, front 6550 7.35 vac second 6.33 vac.
well the oscellation returned with voltages of 5.34 on one tube and the other 5.6vac
I'm pretty much done with this thing. Thanks for all your help today. I will get hold of the manufacturer tomorrow and see what I can do about.
This isn't my first kit, probably my 9 or 10th kit and the first one to not work on me. Frustrating as heck. O well back to the dynaco 70 tonight.
Well Brian is sending me another power tranny in the next week. I will keep you all posted. Thanks again for your help.
Thanks for the heads up.
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