It should be ~6 between 4 and 9 as well as ~6 between 5 and 9.
If there's zero between 3 and circuit ground and zero between 8 and ground, you have a duff tube or the 10M45 isn't working right. Or the resistors around the 10M45.
If there's zero between 3 and circuit ground and zero between 8 and ground, you have a duff tube or the 10M45 isn't working right. Or the resistors around the 10M45.
There is still a 10K resistor between the 10M45 and B+, so if the tube is conducting at all the plate voltage will not equal B+.
In post #9 the OP states "R13 is reading 234 vdc and R23 228 vdc." If this is the case, then the 12AT7 is working correctly, since those resistors are connected to the plates.
The problem here is "one channel dead." 450 volts on both plates will make both channels dead.
The plates of the 12AT7 have roughly the correct voltage, that means that they are conducting about the right amount of current. The cathodes of the output tubes have the correct voltages. This tells me that all five tubes are operating correctly from a DC perspective.
If one channel is not working, something is breaking the AC signal path WITHOUT affecting the DC voltages. There are only a few things that can do this. The input connectors and wiring, the output (secondary side of the OPT) connectors and wiring, or the coupling caps. We have seen issues here on this forum with expensive boutique caps being open, or leaky, but those yellow Mallory 150's never die.
Something about the hole on C11 closest to the center of the board looks funny. It could be the picture, but it looks too big. Try adding some solder to the gold pad on the bottom of board where the cap's wire passes through. Just a hunch....
Okay, I think I got the problem. I took out the speaker connector from the chassis, I have sound on both channel! But one channel is still weak, there is probably a short with rca input too. I will look at this later...enough for today. I've should have look at this before! All those screw are probably in contact with the chassis (that was professsionaly painted at my job...)I need to isolate it a better way.
Update: I insulated the connectors and screwed them tight. Now the sound is equal on both side.
Music on this amplifier is amazing, we can ear each instruments separately and great 3d imaging throught the room even with cheap speakers.
Thanks to everyone who contributed to this thread!
Music on this amplifier is amazing, we can ear each instruments separately and great 3d imaging throught the room even with cheap speakers.
Thanks to everyone who contributed to this thread!