Greetings,
Hopefully this is the right place for this, and apologies in advance for the noob-ish question... I'm repairing a tube guitar amp (schematic attached) which uses a regulated 12VDC supply to power the preamp tube heaters, some relays, a fan, and some logic/switching stuff that is out of my depth of understanding (although I'm willing to learn).
Anyway, the regulator for this 12V supply is supposedly a 2N3055 in what appears to be a TO-220 case, bolted to the side of the chassis. The collector connects to unregulated ~20VDC, the base is connected to a 13V zener to ground, and the regulated 12V (I guess more like 12.4) is taken from the emitter. This part of the circuit is near the bottom left of the schematic.
So the 2N3055 in this amp is dead, shorted base to emitter.
What I'm having trouble with is finding a replacement in the same form factor. Seems like 2N3055 is only available in a TO-3 case. I found an alternative, TIP3055, which is in a TO-247 case, but I'm not sure if that would be an appropriate substitute...
I'm also wondering why they used such a high-power part (~100 watts, 15A) in what seems like a low-power application (600mA for the heaters, plus a little 12V fan and a couple relays and logic stuff). And if it was indeed overrated for this application, why did they choose it and why might it have failed?
I'm going to go ahead and order a few TIP3055's, but if anyone could give me some reassurance that that's an okay substitute, or suggest a better alternative, it would be very much appreciated.
Thanks in advance!
Hopefully this is the right place for this, and apologies in advance for the noob-ish question... I'm repairing a tube guitar amp (schematic attached) which uses a regulated 12VDC supply to power the preamp tube heaters, some relays, a fan, and some logic/switching stuff that is out of my depth of understanding (although I'm willing to learn).
Anyway, the regulator for this 12V supply is supposedly a 2N3055 in what appears to be a TO-220 case, bolted to the side of the chassis. The collector connects to unregulated ~20VDC, the base is connected to a 13V zener to ground, and the regulated 12V (I guess more like 12.4) is taken from the emitter. This part of the circuit is near the bottom left of the schematic.
So the 2N3055 in this amp is dead, shorted base to emitter.
What I'm having trouble with is finding a replacement in the same form factor. Seems like 2N3055 is only available in a TO-3 case. I found an alternative, TIP3055, which is in a TO-247 case, but I'm not sure if that would be an appropriate substitute...
I'm also wondering why they used such a high-power part (~100 watts, 15A) in what seems like a low-power application (600mA for the heaters, plus a little 12V fan and a couple relays and logic stuff). And if it was indeed overrated for this application, why did they choose it and why might it have failed?
I'm going to go ahead and order a few TIP3055's, but if anyone could give me some reassurance that that's an okay substitute, or suggest a better alternative, it would be very much appreciated.
Thanks in advance!
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