Fisher R-20 Resistor R59 Source. You know, the double-ended tall one

rsaxvc

New Member
On the top of an R-20 amp there's a tall power resistor, R59, right next to the rectifier tube, but electrically separated by a 50 ohm R66. R59 is effectively two power resistors, a 5500 ohm and a 100 ohm. Mine is cracked.

Symptom is that all tubes glow ( 6v rail working fine ), but zero sound comes out(no crackle, no hiss). I suspect this cracked resistor is the culprit, as its a series part of the DC regulation stage. Effectively, the tubes have no DC to work with(untested assumption)

Is there a source for these? Anyone have one they'd let go of? Would love to keep it looking original.

Alternatively, would it be a big problem to replace it with a 5600 ohm and a 100 ohm? What power ratings would these need to be? Which side is the 5600 ohm(I assume this heads toward the FM receiver), which side is the 100 ohm(Assume this heads towards the PA / output transformer)?
 
Best bet is to leave the existing resistor in place disconnected, and then replace with separate resistors underneath. R59A is connected between C43B and C43A. R59B is between C43A and C43C. 3w is most likely fine for both. I tend to wattage's a little higher than what's shown on the parts list for the P.S. string. You'll have to test the individual sides to determine which is which for sure. I would presume the 5.6K is R59A and 100ohm is R59B, BUT it could be the reverse.

If you can find someone with a R20 parts chassis, you could get that dual resistor and install it. I couldn't find a 3w or 2W with a voltage rating of >200v so I picked 2 - 5Watters. These will do very well.

Ohmite 5.6K ohm 5W wirewound. Mouser #588-45F-5.6K $2.11 Rated to 460v

Ohmite 100ohm 5W wirewound Mouser # 588-45F100E $1.45. Rated to 460V
 
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