Well I won't deny that could be a solution too, however it's much easier to take C513/514 out than fitting a couple extra in the needed spot.
Did som messing around with transistors Q503/504 was going to swap them with each other first, but lost track so went right ahed and tried some ZTX450´s instead.
This seem to work very well, at least amp is completely silent and seems stable, even plays music.
Now question is, should I call it a fix and move on, or try to get it to work with the original transistors? Thing is I still find it odd original transistors can be the real cause of this, like out of the blue. Especially since they work fine in some situations.
Suggestions are still greatly appreciated 🙂
Did som messing around with transistors Q503/504 was going to swap them with each other first, but lost track so went right ahed and tried some ZTX450´s instead.
This seem to work very well, at least amp is completely silent and seems stable, even plays music.
Now question is, should I call it a fix and move on, or try to get it to work with the original transistors? Thing is I still find it odd original transistors can be the real cause of this, like out of the blue. Especially since they work fine in some situations.
Suggestions are still greatly appreciated 🙂
I'd declare victory and enjoy! You can always revisit if the need arises.
Old semiconductors can deteriorate. Maybe this is one of those occaisons.
Old semiconductors can deteriorate. Maybe this is one of those occaisons.
Good point, guess I could at least do some listening tests at this point before I decide. Maybe I should put it to work till over Christmas to see how it holds up.
I don't think its transistors I believe it is just Q503 that has changed parameters . It would be interesting to diode check the 2 BC149Bs as you say you have lost track of which is Q503 . Q503 had an seemingly low BE voltage but I put this down to it oscillating .
I agree keep the ZTX450s .
I let the ZTX450s stay, they do the job just fine I think. Maybe I take a closer look at the old 149b over Christmas and see if I can find anything suspicious about them, but I don't think they'll be going back anyway.
I Want to thank all who contributed, all suggestions were greatly appreciated, but a little extra thanks to epicyclic, BSST and Osvaldo for also following up till the end, so thanks again and merry Christmas!
I Want to thank all who contributed, all suggestions were greatly appreciated, but a little extra thanks to epicyclic, BSST and Osvaldo for also following up till the end, so thanks again and merry Christmas!
Me too.