Voltage question - no love at 21

[TexasRugger]

I did the voltage test and everything checked out fine except the measurement at 21.  I triple checked the wiring.  Could I have damaged the rectifier when soldering?  I get good measurements at 19 and 20.  Amp works and sounds great - am I maybe just not getting a good reading?  Thanks,

Tex

 

[aristos_achaion]

What're you getting at 21?

 

[Dyna Saur]

If you don't have any voltage on 21 (the +  output of the bridge rectifier) then there shouldn't be any voltage "downstream" on 15 and 13. FWIW, I get 213V on 21, 191V on 15, and 170V on 13 (the operating B+ voltage).  The 6CG7 plates run   at about 84VDC,  the cathodes at 1.53V, and the 6080 cathodes sit at  about 106 and 107VDC.  

Roughly stated, the 6CG7 draws about 4 mA each channel, and the 6080 about 35-36 mA / channel. For a total of about 78-80 mA current consumption from the PSU.  

/ed B

 

[Grainger49]

I have to ask, did you check here:

http://www.bottlehead.com/smf/index.php/topic,657.0.html

The correction that applies here is, "Attach one end of a second 270 ohm 5W resistor to terminal 21U (NOT 22U)."  If you get nothing at 21 this could be the problem.

 

[Dyna Saur]

22U (or 22L) is connected to one of the mounting screws for the power trannie, so it would be at ground potential.     Presuming that the + output (21) from the rectifier isn't connected to 22 in any way, there should be no harm done (and no B+ downstream). Maybe 21 has some flux / junk  on the surface which prevents you from getting a good probe contact?

OTOH, you state that the amp is working and sounds good.  Check 15 and 13,  they should be around 191 and 170VDC, respectively.  Each 270  ohm resistor  should drop about 21 VDC, if everything is running properly.

/ed B

 

[TexasRugger]

Thanks everyone.  I really don't know how to explain it.  I figured that if everything else downstream worked and measured fine (which it does) then it must be a bad reading on my part.  Amp is working and sounds great!  Thanks again,

Tex
aka Steve