I am working on a Yamaha M-60 amp and need to replace a 2SC2634, the closest I can find is BC546 (which I have and I know the pinout is different). I got the schematic from HiFiEngine and it is very fragmented. TR140 is the bad one. Anyone have a better idea?
Both voltage & current demands / issues are relevant here, so better post the full circuit in advance of an advice on this matter.
Right that these are only 0.05A vs 0.1A for the original, in this case stick with the BC546 since they have about same VCE
as the originals, although there s a 10k resistance with the emitters and this point to a current that cant be more than say
a total of 12mA for the transistor pair assuming a 120V voltage, wich is doubtfull given that the 2SC2634 stand only 60V,
so the total current cant be more than 6mA, or 3mA per transistor if it s balanced.
as the originals, although there s a 10k resistance with the emitters and this point to a current that cant be more than say
a total of 12mA for the transistor pair assuming a 120V voltage, wich is doubtfull given that the 2SC2634 stand only 60V,
so the total current cant be more than 6mA, or 3mA per transistor if it s balanced.
Right, you shouldn't exceed the collector current rating in that circuit. It is overcurrent detection, if you lose the emitter resistors (which I assume happened), whatever is there will probably fail.
Yeah I already replaced 5 transistors in the right channel output section in addition to drivers, caps and resistors. The further I dig the more I find, 15 components so far. I am working on this for a friend, he got it from someone that said his cat did something to it. I think the speaker connection for the right channel was shorted somehow.
I found someone on ebay with good feedback ratings that has some 2SC2634. I hate getting semiconductors there but might in this case.
I would use 2SC2240 or 2SC1845.
I used to do warranty for Yamaha. Those tend to blow "stem to stern". Replace the diff pair with a closely matches pair to keep DC offset down. Increase the current capacity of the emitter resistors, when they open, you get far more damage. Non-inductive types. We lost our shirts at warranty rates on those types of amps.
I used to do warranty for Yamaha. Those tend to blow "stem to stern". Replace the diff pair with a closely matches pair to keep DC offset down. Increase the current capacity of the emitter resistors, when they open, you get far more damage. Non-inductive types. We lost our shirts at warranty rates on those types of amps.
Yeah, the transistor type is not critical in that position. Fusible emitter resistors are a double edge sword. They might prevent the PCB from going up in the biggest ball of fire since the last sun in these parts exploded, but open emitter resistors will often cause a lot of additional damage. This current limiting circuit is a little wonky anyway and subject to failure. The more traditional VI limiter can be made “mostly” bulletproof, provided that the VAS current is limited (if not, expect a mile long string of Black Cats). Properly designed, The failure would be limited to one miserable 1/2 or 1/4 watt resistor when faced with an open emitter resistor (transistor would survive).
Yamaha made many errors back then, probably CSA idiotic demands are the reason we had to deal with those emitter resistors. That and light traces on the PCB. These were not nearly as good as the product we were used to seeing from Yamaha. Their M.I. products from the same era were made very well. Hard to believe it was the same company.