EastPoint mentioned the big resistor, I noticed that also, and that the thermistor is no longer strapped to it. Bad sign. The fact that someone has fairly recently replaced the big capacitors tells us that someone's been in there, and that the workmanship is not indicative of care and quality.
The SX-1250 uses that "big resistor" to slowly charge the big capacitors, if it gets too hot the thermistor will shut it down IIRC. They need to be strapped together.
When the big caps are charging through the resistor the soft-start relay should be open. If someone has bypassed the soft-start relay then the receiver will pull over 100A at the power cord momentarily, making a flashbulb out of the 12a fuse (original is a ceramic fuse, not a glass one, so that too has been replaced).
Here's my theory: The receiver had leaky main caps, drew a lot of current during start-up, made that resistor warm many times but made it through the soft-start eventually, and worked. As the capacitor(s) got worse, eventually the receiver didn't start. Possibly burning up that resistor. Maybe the soft-start relay's contacts welded closed, maybe the "tech" who repaired it bypassed the relay, but I have a feeling that the soft-start relay is causing the high-current / blowing fuse (this is probably more hope than anything). Ensure that this relay is not bypassed and not shorted.
And yes, as others have mentioned you need a current-limiter if you're going to buy or work on this stuff, the SX-1250 will need at least a 100w bulb to come out of protection. My suggestion is to build one, mine cost me around $60 in parts and allows me (through switches) to parallel bulbs, turn it completely off, or bypass for full power giving me a very soft start through 40w or up to 200w, and flip the bypass switch to have full power and check voltages. Also avoids constant plugging-unplugging when restoring, and the 40w is excellent for reforming capacitors in old tube gear (as is a vairiac of course).
The SX-1250 uses that "big resistor" to slowly charge the big capacitors, if it gets too hot the thermistor will shut it down IIRC. They need to be strapped together.
When the big caps are charging through the resistor the soft-start relay should be open. If someone has bypassed the soft-start relay then the receiver will pull over 100A at the power cord momentarily, making a flashbulb out of the 12a fuse (original is a ceramic fuse, not a glass one, so that too has been replaced).
Here's my theory: The receiver had leaky main caps, drew a lot of current during start-up, made that resistor warm many times but made it through the soft-start eventually, and worked. As the capacitor(s) got worse, eventually the receiver didn't start. Possibly burning up that resistor. Maybe the soft-start relay's contacts welded closed, maybe the "tech" who repaired it bypassed the relay, but I have a feeling that the soft-start relay is causing the high-current / blowing fuse (this is probably more hope than anything). Ensure that this relay is not bypassed and not shorted.
And yes, as others have mentioned you need a current-limiter if you're going to buy or work on this stuff, the SX-1250 will need at least a 100w bulb to come out of protection. My suggestion is to build one, mine cost me around $60 in parts and allows me (through switches) to parallel bulbs, turn it completely off, or bypass for full power giving me a very soft start through 40w or up to 200w, and flip the bypass switch to have full power and check voltages. Also avoids constant plugging-unplugging when restoring, and the 40w is excellent for reforming capacitors in old tube gear (as is a vairiac of course).
