That is true, but I do still want the volume knob on the receiver to control audio output. I tried putting the transformer in series with the 12AT7 plate and it worked pretty darned well except it had reduced bass response. I then tried bypassing the 12AT7 stage and got more distortion than usable audio. I then put it back the way it was originally and it works good.
By looking at the schematic I don't see any reason for there to be a small bit of audio on the local output when the local volume control is turned full CCW. Is a small bit of audio on the local audio output normal whent he volume control is turned full CCW or is there a problem with my receiver?
If I can get the audio down to zero when the conterol is turned full CCW I can then drive a more powerful external amplifier. I even tried just using a 15K balanced/unbalanced transformer driving a pair of 6BQ5 tubes in push pull and still got audio with the volume control turned full CCW. I'll have to study the schematic and see why I still get audio.
Also I noticed that under certain conditions the voltage reference tubes will glow and not glow as though the tube was connected across a capacitor and being charged through a high value resistor. Is that normal or is there a problem?
I also used a variac to knock down the voltage to 115 Vac.
I do notice that if I have the volume control down to full CCW and I turn the RF control up full I get more hum in the speaker and also the Ac voltage on the 180 Vdc test jack increases to around 7-8 Vac. Is that a normal indication or is there a problem?
I know the vitimin Q caps are still good, but are there any other capacitors that need to be replaced?
Also are there any resistors that should be replaced?
Here's the schematic of the audio amp. Maybe y'all can explain to me why the audio from the local out is not completely zero when the local audio volume control is full CCW. Also I noticed that with the local audio control set to full CCW I can turn up the line audio control and hear some audio through the speaker connected to the local audio output. Sounds to me like maybe a bypass capacitor somewhere is going bad. I can see maybe one thing I need to do. The 12AT7 section used in the local amp has its 180K plate resistor connected to the same line that feeds B+ to the output tubes. Maybe I need to insert a 5K resistor or a little higher and then a filter cap after that. Also looking at the schematic if the 1uF filter cap in the plate circuit of the 12AU7 buffer stage or the 10uF filter cap on the line that feeds the output tubes were bad I suppose that I could get crosstalk between both audio channels.
I used a 15K resistor in series with the 180K and a 22 uF 450 volt cap to ground and the audio no longer bleeds over from the line output to the local output.
I just noticed and one of the rectifier tubes is no longer lit up
Would it be ok to simply sub diodes or should I look for another 26Z5 tube? I can get the proper diodes at Radio Shack tomorrow. Thinking about it that tube being bad (not sure when it went bad) could have been the cause of the audio issue and certainly is the cause of the increased hum from the speaker.