Fisher 202 Futura Series

[Tube Radio]

I have a Fisher 202 Futura Series receiver I recently recapped. Works great except I have a problem which I do believe was there before the recap.
The receiver will not go into FM stereo, but I can touch my meter probe to the lead of a certain resistor on the FM MPX board and the receiver will go into FM stereo and stay there until I switch to mono and back to stereo. So far everything looks good except a few voltages on the FM MPX board are a little off. I noticed that on the schematic there is a 27K resistor and a 4.7 K resistor both with an asterisk beside them denoting that those parts were not used in all receivers. For receivers without those parts there is a 10K resistor in place of the 27K resistor. When I just use the 10K resistor the receiver goes into stereo properly. Even though that works and would be acceptable according to the schematic I still want to know why it don't work with the 27K resistor and 4.7K resistor. Looks like I may be desoldering and checking resistors to see if any are out of tolerance as that is the only thing I can think of that can be the problem.

 

[Tube Radio]

I got the other caps I forgot to order replaced and the receiver sounds great.

I was gonna make an external box that would sum the right and left speaker channels for a subwoofer output, but decided to mod the receiver as shown in the picture. One ground terminal for the remote speakers is used for the summed signal and the other ground terminal is still ground. If the signal level is too hot for the subwoofer amp I can just put a resistor across the output terminals where the cable for the subwoofer amp will connect. The mod is totally reversible by removing the resistors and connecting the ground terminal back to ground. I did add a couple 220 uF caps in the receiver to function as a high pass crossover since this will be used with a sub. I disconnected the wires to the remote speaker terminals and connected the 220 uF caps in series with them. Then I connected the wiring and 1K resistors to the positive terminal of the caps with the negative terminal going to the remote speaker terminals. I now have a full frequency output on the main speaker terminals along with a hp output & subwoofer output on the remote speaker terminals. Unfortunately I didn't take a picture with the caps installed and am not going to do it now that the receiver is put back together. I am still waiting on the new 2200 uF speaker coupling caps which were back ordered.

I figured out what the variable resistor on the driver board is for. It allows you to set the collector voltage of one output transistor to balance the amp. My B+ voltage is 61.5 Vdc so I divided that by 2 and adjusted the variable resistor to set the collector voltage of one output transistor to 30.75 Vdc. Unfortunately the service manual I got from Radio Museum does not have instructions on how to adjust that variable resistor, but I am pretty sure I have it set right as on the schematic it lists 31 Vdc at the collector of one output transistor (TR07 on schematic) with a B+ of 62 Vdc. The receiver does seem a little stronger now.