Have you tried looking at All Transistors. Datasheet. Cross Reference Search. Transistor Database. They have a link to 'equivalent transistor' which searches for similar spec items. I find it useful for hunting unobtainium replacements.
here is my replacement:
2sc897 = 2n3773
2sa606 = 2n5416
2sc959 = 2n3440
2sd427 = MJ15001
2sb557 = MJ15002
2sc897 = 2n3773
2sa606 = 2n5416
2sc959 = 2n3440
2sd427 = MJ15001
2sb557 = MJ15002
They look reasonable at a quick glance. I wondered why you needed the 2N3773 and the MJ's but of course you had two different amps.
Should be OK but as always, proceed with caution, and use that bulb tester.
Should be OK but as always, proceed with caution, and use that bulb tester.
If you've tested the old transistors and determined they are bad, you can go to your favorite transistor dealers website and they usually have a replacement listed on the same web page. There are a couple websites that I'm familiar with that sell these old transistors, Little Diode is one that I remember. Not cheap, but you get the real thing. BTW- having rebuilt my Marantz 1060, I know those transistors listed in post #22 will work.
The old semiconductors varied much because the modern devices used for semiconductor processing, such as mass flow controllers, weren't as accurate back then or non-existent.
Buy a batch of transistors from the same lot and they will have the same Hfe value. Marantz engineers called for matching Hfe on their driver and output transistors and will usually state the value on their schematics and technical manuals. That other website you mentioned has a lot of tribal knowledge about this that they hold close to their chest because they want you to send the amp to them to repair. You can fix it yourself if I can do it. I'm not an EE or tech, but I did repair the two Marantz units I have and they are still used daily for the past 10 years.
The old semiconductors varied much because the modern devices used for semiconductor processing, such as mass flow controllers, weren't as accurate back then or non-existent.
Buy a batch of transistors from the same lot and they will have the same Hfe value. Marantz engineers called for matching Hfe on their driver and output transistors and will usually state the value on their schematics and technical manuals. That other website you mentioned has a lot of tribal knowledge about this that they hold close to their chest because they want you to send the amp to them to repair. You can fix it yourself if I can do it. I'm not an EE or tech, but I did repair the two Marantz units I have and they are still used daily for the past 10 years.
Agreed but, generally, first power up involves a no load situation. I'd expect that's relevant but even so, it makes sense that a big amp will require some bulb wattage.
The bigger the amp, the bigger the bulb, true. But most “200 watt per channel” and smaller amps are just fine with a 100 watt bulb. Amps that normally run hot and are supposed to be biased high or PA amps that put out multiple kW will require more - a 500 watt toaster can be used. Or a bank of old PAR38 floodlights (from an old disco lighting system - Keeping the old bulbs for that purpose). Those types of amps have more power transistors in parallel, and the fault current per device about the same as a smaller amp on a 100 watt bulb. Biggest amps I’ve ever dim bulbed was a 1300 watt QSC and the old CS800, And both were happy with a 100 watt. My CA18’s would not be, but the only faults I’ve ever had to track down were non life threatening (bad relay timing caps and dying fans).
Toaster elements use nichrome heater wire, which has roughly constant resistance on heating, unlike tungsten bulbs where the resistance rises by a factor of 10 or so from cold if the amp's a short. In other words it won't be as good a tester as 5 x 100W bulbs.
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