Hi Everyone,
Picked up an old & very dirty Pioneer SA-7500ii showing signs of past mishaps. The original output transistors 2SB618A & 2SD588A are present on one channel, but on the other channel they have been replaced with SC2579 & SA1104, with a hole drilled in the heatsink to mount them. From the filth & dust build-up it must have been done a long time ago. Also one of the emitter resistors is is not original & the board is quite severely charred beneath this resistor, so probably from the time of the original failure.
Has anyone ever heard of these transistors being used as a sub for 2SB618A & 2SD588A and should they be OK ? On paper the specs look ok & to be fair the amp seems to work ok. Should I just leave them in or replace all 4 transistors with new ones ?
I know on various forums other replacements transistors are proposed, but to be honest most are not easily available at a reasonal cost. I can quite easily get 2SC3858 & 2SA1494 though. Any advice welcome.
Picked up an old & very dirty Pioneer SA-7500ii showing signs of past mishaps. The original output transistors 2SB618A & 2SD588A are present on one channel, but on the other channel they have been replaced with SC2579 & SA1104, with a hole drilled in the heatsink to mount them. From the filth & dust build-up it must have been done a long time ago. Also one of the emitter resistors is is not original & the board is quite severely charred beneath this resistor, so probably from the time of the original failure.
Has anyone ever heard of these transistors being used as a sub for 2SB618A & 2SD588A and should they be OK ? On paper the specs look ok & to be fair the amp seems to work ok. Should I just leave them in or replace all 4 transistors with new ones ?
I know on various forums other replacements transistors are proposed, but to be honest most are not easily available at a reasonal cost. I can quite easily get 2SC3858 & 2SA1494 though. Any advice welcome.
Wow.
Now I have to look in mine(gulp!).
Cleaned switches,pots, etc several years ago. Nothing jumped out at me then, but I have since had
an sx828 horror story.
Now I have to look in mine(gulp!).
Cleaned switches,pots, etc several years ago. Nothing jumped out at me then, but I have since had
an sx828 horror story.
The only thing special about those original transistors is the weird package. Pretty much any modern audio type in a TO-3P will work if you‘re willing to drill the heat sink. Use what you can get easily.
Thanks wg-ski for the advice, yes that's pretty much what I could read.
Actually I hooked the amp up to some speakers and it sounds OK, so although the original repair done some years ago works looks odd, it was effective.
I am thinking just to change out some of the ill looking caps & the one emitter resistor
Actually I hooked the amp up to some speakers and it sounds OK, so although the original repair done some years ago works looks odd, it was effective.
I am thinking just to change out some of the ill looking caps & the one emitter resistor
Yeah, I’d probably swap out that one odd emitter resistor, for the same type as the other three. That old one was probably stressed at some point if the others actually failed. Same as the caps, if you’re in there anyway you get rid of any ancient small electrolytic, just so you never have to go back and fix it again.