Those are thermistors, not varistors.
The other ones are STV-3s. Just use 3 1N4004s in series, but be careful mounting them! Shorts to the heatsink are bad. As in "blow the amp up" bad. Had to do this in a Sansui 4000 a few years ago. Unit was "gotten to" and both channels blew up. Had to rebuld both driver boards with modern components. Only one board had a blown trace- a simple jumper fixed that. I used thermal epoxy to mount the bias diode assemblies to a heatsink on each driver board.
The Sanyo 1056 does not have thermistors in the amp, only STV-3s. Look at the schematic.
It's actually one of the easier units to work on, just maybe not the thing for a beginner. Finished a Fisher 500T recently- what an adventure... Those stupid "flat pack" (think SIP TO-92) transistors on the autoscan board were bad.
Shotgunned all of them, autoscan repaired.
Was a bear to align, since the trimmer caps in the front end module were this close to coming apart- got lucky and got it much better.
IF alignment wasn't too bad, but had to "improvise" with sig gen and 2nd harmonic of xtal oscillator- remember, front end was slightly off, even after I got it better. MPX was okay, thank goodness- I don't have an MPX gen.
Power amp board pulled, resoldered, washed. Driver transistors got new thermal compound, new zener for derived voltage, larger/safer resistors for driver transistors- originals were marginal. 21195/96 output transistors.
Power supply upgraded- bigger diodes, larger caps, and minor-rail reg transistor replaced with one having greater SOA, and put on a larger heatsink. Entire board resoldered, cracks epoxied, board washed.
Tone control and autoscan boards also resoldered and washed.
All controls cleaned, all caps replaced. The only thing in that unit untouched was the AM RF board. The ferrite loopstick was "lost" years ago; decision by owner was made to abandon AM.
Also cleaned up wiring from AC socket to switch/transformer, and from transformer to PS board- also added the full compliment of PS fuses.
TG- yours is an easy unit to work on, but if you get frustrated and/or "make do" with the wrong tools, you'll only make things hard for yourself.
Originally posted by TG
Don't drop a dollar to pick up a dime- meaning, don't go cheep on soldering equipment. And, for your sanity, do NOT get a cheep aoyoue thing- if they were a power supply, they'd make Deers look like NASA-spec stuff.
AVOID AOYOUE like the plague.
Leave a comment: