Zenith 10S690 Volume Control Issues

[Kevin Kuehn]

Originally Posted by vortalexfan

Actually I think the schematic is wrong, because in the radio itself both IF cans go to only ONE SIDE of R11, and I didn't touch that wiring except to replace the old dry rotted wire from the 1st IF can and I just wired that wire back to where it was previously, and I didn't touch the wiring to the 2nd IF Transformer because the wiring was fine in it.

I don't think the schematic is wrong. You'd better retrace your wiring and verify where both ends of R11 terminate.

[vortalexfan]

Originally Posted by Kevin Kuehn

I don't think the schematic is wrong. You'd better retrace your wiring and verify where both ends of R11 terminate.

I did, and only one end of R11 terminates to both IF Cans.

Riders is known for making mistakes in their service data, so I wouldn't put it past them to accidentally misdraw the schematics.

[Kevin Kuehn]

Originally Posted by vortalexfan

I did, and only one end of R11 terminates to both IF Cans.

Riders is known for making mistakes in their service data, so I wouldn't put it past them to accidentally misdraw the schematics.

Fine if the radio works like that, but the Riders schematic makes sense as shown. The right end of R11 has audio present and the left end becomes the filtered AVC voltage that would normally be feeding the grids of the RF and 6K7 IF amp.

[old_coot88]

After finally deciphering the switching subnote below the main schematic, and correctly drawing it (finally in post# 83), R11 is not relevant to the discussion since it's not involved in the switch circuit.

The second gang of the switch is used for switching mixer (6A8) screen grid voltage on/off as shown:

[jr_tech]

Originally Posted by Kevin Kuehn

Fine if the radio works like that, but the Riders schematic makes sense as shown. The right end of R11 has audio present and the left end becomes the filtered AVC voltage that would normally be feeding the grids of the RF and 6K7 IF amp.

Perhaps that second “IF can” is actually the antenna coil?

The schematic appears to be correct, from my understanding of the typical AVC circuit design.
jr

[Kevin Kuehn]

Originally Posted by jr_tech

Perhaps that second “IF can” is actually the antenna coil?

Now there's a real possibility.

[vortalexfan]

Originally Posted by Kevin Kuehn

Fine if the radio works like that, but the Riders schematic makes sense as shown. The right end of R11 has audio present and the left end becomes the filtered AVC voltage that would normally be feeding the grids of the RF and 6K7 IF amp.

Either that or my set was a Friday special and was miswired from the factory but wasn't caught by Quality Control because it still worked that way...

[Kevin Kuehn]

Originally Posted by vortalexfan

Either that or my set was a Friday special and was miswired from the factory but wasn't caught by Quality Control because it still worked that way...

I'm more leaning towards this.

Originally Posted by jr_tech

Perhaps that second “IF can” is actually the antenna coil?

[vortalexfan]

Originally Posted by Kevin Kuehn

I'm more leaning towards this.

It would explain why this thing is acting up like it is.

[dieseljeep]

Originally Posted by Kevin Kuehn

I'm more leaning towards this.

I would wire it per the schematic. You stated there was an issue with the AVC not working properly.

[vortalexfan]

Originally Posted by dieseljeep

I would wire it per the schematic. You stated there was an issue with the AVC not working properly.

Yeah. The audio would fade in and out even though there wasn't anything wrong with the signal.

I was thinking it was a problem with the AVC bypass cap being leaky but if you would of seen the condition of the original capacitors in this radio and the fact that it had almost all of it's original tubes in it yet, I'm beginning to wonder if this radio was a low hours set because of that wiring issue and AVC problem.

[Kevin Kuehn]

Any update on jumping those two switch contacts per old_coot88 directions? Undoubtedly you have two short lengths of wire, resistor clippings, anything?

[vortalexfan]

Originally Posted by Kevin Kuehn

Any update on jumping those two switch contacts per old_coot88 directions? Undoubtedly you have two short lengths of wire, resistor clippings, anything?

Not yet, been kind of busy the last couple of days.

Plus, I've been kind of taking a break on working on the radio part to try and work on the record player drawer trying to figure out how best to make some modern euro style drawer glides work with the record player drawer since the original drawer glides were broken and they were a custom job for this unit.

[jr_tech]

How many “IF cans” do you see on the radio chassis?
What does the other end of r-11 appear to be connected to?



jr

[vortalexfan]

Originally Posted by jr_tech

How many “IF cans” do you see on the radio chassis?
What does the other end of r-11 appear to be connected to?



jr

There's 2 IF cans and a 3rd can that looks like it should be an IF can but it doesn't have any trimmer caps on top like the actual IF cans do, it appears to be just a coil of some sort inside and that's it, no trimmer caps on the bottom either, maybe the RF Coil?

The other side of R11 from what I could see looked like it attached to the tone control panel/circuit somewhere.