Posts: 76
Threads: 20
Joined: Oct 2010
City: Oskaloosa
State, Province, Country: KANSAS
I am restoring a 40-185; all the caps and rubber wiring has been replaced; the set has been aligned and plays well with only some minor audio distortion. I have checked the voltages on the tubes and discovered they are about 20 to 30 volts low. I have also found the RF Coupler #13 on the Riders is only reading .5 ohms and should be at 3.5. Would this cause my low voltage? Can I rewind the RF coupler, and if so how to do it and what wire size should is use? If this could not be causing my voltage draw, then what else should I look into.
Thanks
Skip
Posts: 1,394
Threads: 69
Joined: Oct 2007
City: Linn Creek, MO
Hi Skip,
The RF coupler item # 13 will not cause your voltages to be low. Did you replace all the capacitors or just the filters? Make sure the polarity of the filter capacitors are correct. Check the voltage on the control grids of the output tubes, if high, it will cause the output tube to draw too much current and pull the voltage down. If that is the case look at capacitor # 46.
Steve
M R Radios C M Tubes
Posts: 76
Threads: 20
Joined: Oct 2010
City: Oskaloosa
State, Province, Country: KANSAS
Steve thanks for the heads up. I had replaced all the caps and double checked the ground on the e-caps. I did discover a cold solder and a bad new cap. I also discovered I had tied resister #49 to the ground at resister #59 instead of #60. Once i fixed those issues my voltages are right inline.
If I wanted to rewind #13 the RF coupler, what type of wire should I use? I have removed the wax coating and found the break in the wire, but it is so brittle that I can not splice it back together without breaking it in another spot. The radio plays with out the RF coupler in, on BC, have not really tried the SW bands yet, is the RF Coupler needed for the SW bands?
Skip
