sx 1050 pops on start up

[markthefixer]

Stick with the original plan.

The +60 and +30 are working fine. If the -60 and -30 were working right they would be mirror images... notice the symmetry between the two sets of circuits.

Q5 could be good, or damaged almost to the point of failure. Q7 looks completely shorted, and Q6 could be, or not - your readings aren't precise enough (13v leaves some doubt, 13.00v doesn't and 0.1v can be significant) to tell for sure.

Q11, by the way, was e20.5, b17.2 and c6.26 ?

it would make more sense if it were :
Q11, by the way, was C 20.5, b17.2 and E 6.26 ?
even though Q11 IS ZAPPED.

Are you sure you have the lead orientation correct - originals versus replacements may be different, ALWAYS go by the board symbol markings.
THEN reference the parts orientation from the (original - IN the service manual) data sheet.

reread post 11 in this thread, I just marked the symbols.
http://www.audiokarma.org/forums/showthread.php?t=43186

that's IT for now, I have to get BACK to the bench.

[steamwhistle]

Yes, I know how to mount transistors correctly. I've put new caps and transistors etc. in amp boards with no trouble. This power supply thing is a mystery. I'll have to lay off it about a month or so. Too bad, because the old 1050 was a great voice in my workshop for years.

I did notice one thing, though. While I was cleaning up my workbench I found a spare unused 512-ksc945clta to-92 still stuck on the cardboard strip. I pulled it off just to practice with a meter. The meter, set on diode, wouldn't read it, no matter what lead I used. It would read four other transistors lying about on the counter, but not the 945. I'm wondering if I got a bad batch of 945s. There are three of them in the power supply. I put this one by itself into the board just to see what readings I would get off it and what I got was a new short. Fuse three and four blew. I've ordered a new batch of transistors and diodes, and I'm starting to wonder about the resistors. See you in a month.

[markthefixer]

Hope you took my bench comment the way it was intended: I didn't want you expecting another reply that evening and waiting for it. Sort of saying "last hand for me" in a poker game..... probably could have said it better and differently.

512-KSA733LBU to-92 eBc 50v .15a .25w 180mhz 40-700hfe $0.05 ea bu = bulk

512-KSA733CLTA to-92 eCb 50v .15a .25w 180mhz 40-700hfe $0.05 ea ta = ammo strip

notice the 733lbu has eBc, while 733clta has an eCb layout... that has tripped up the best of us, myself included.

As for the rest, my confidence in my assessment of how much hand holding was needed on this thread was shaken, and I was hit with a case of the guilts....

[steamwhistle]

Oh. So the 512-ksa733clta on your list, and noted there, as "ebc layout" is really ecb. Well, that explains the lack of music in my workshop. I'm glad that's solved.

The Fairchild data sheet on this transistor is misleading to a non-expert. At the top of the page it says KSA733 in big letters and then there's a picture of the little darling marked EBC. However, in smaller print on the left side of the page it says "Suffix "-C" means Center Collector" i.e. ECB

I figured it was something simple.

[markthefixer]

Originally Posted by steamwhistle

Oh. So the 512-ksa733clta on your list, and noted there, as "ebc layout" is really ecb. Well, that explains the lack of music in my workshop. I'm glad that's solved.

The Fairchild data sheet on this transistor is misleading to a non-expert. At the top of the page it says KSA733 in big letters and then there's a picture of the little darling marked EBC. However, in smaller print on the left side of the page it says "Suffix "-C" means Center Collector" i.e. ECB

I figured it was something simple.

oh %$#*, my fault... that %$%# old data..... I fixed it, but not in all it's incarnations...

In retrospect - my personal procedures involve function testing each transistor before installation - and in the process the lead identification is confirmed. Before I power up it's always triple checked as it's quicker and easier to check than to troubleshoot.

Guess I haven't hammered on testing before installation lately.... and should have...