sx 1050 pops on start up

1050 pops

I changed the diodes on the fuse board you told me to. Still humming. I took a power supply reading, which was faulty as follows:
1. 23
2. 80
3. -80
4. 0
5. 19.6
6. 19.6
7. -13
8. -13.8
9. -6.1
10. -5
11. -5
12. 0
13. 24.8
14. 24.9
15. 31
16. 61
17. 61
18. 10.6
19. 10.7

Hmmmmmm I'd appreciate any hints here about why she's humming.
 
What happened is that all the regulators except the +60, +30 etc are zorched.

What did you do to the -60v, -30, +13 and +5v regulators.

The -13v on pin 7 is ok at least.

Voltages: read and post, three each: ebc, ground referenced, for Q5, Q6, Q7, Q9, Q10 & Q11.

OR

remove and 6 way diode test those same transistors,

OR

replace them AND D4, ALL AT ONCE.
 
1050 pops

q5= b-13, c-80, e-12.6
q6= e-13, b-13, c-80
q7= e-13, b-13, c-13
q9= b20, c21, e20
q10= e20.5, b20.5, c21.3

for your continued dancing entertainment I re-noted the rest of the transistors

q1= b61.4, c77.4, e60.8
q2= e61.5, c77.5, b62.1
q3= e14.1, c62.1, b14.6
q4= e30.9, c55.7, b31.5
q8= e-6, c-6.4, b-6.5
q12= b10.5, c12, e11.2
q13= e11.2, b11.2, c11.9

All of these are new transistors, though newness is a relative term in this case.
I recall hearing a crackle during one of the recent 5000 maniuplations of this board during testing, so it's possible that pins one or two hit the chassis.
 
You missed Q11.

Replace Q5 through Q11 inclusive, D2 and D4. ALL AT ONCE. Get extra as history indicates the need, plus you'll save on postage. Search previous posts for the parts lists as your penance.

Some may raise questions about a few transistors & readings and need for replacement, but the symptoms of a problem could be masked by the other transistors - and the hard way could result in even MORE destroyed parts. NONE of the parts are over a buck and most are around ten cents, so there's no real incentive to muck about.
 
1050 pops

Thanks. How did the readings look on Q1, Q2, Q3, Q4, Q8, Q12, and Q13?
Q11, by the way, was e20.5, b17.2 and c6.26 ? Any of these look like they need replacing, or does than answer depend on reinstalling q5-11?
 
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 ?
Click to expand...

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.
 
1050 pops

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.
 
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....
 
1050 pops

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. :scratch2:
 
steamwhistle said:
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. :scratch2:
Click to expand...

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...
 
1050 pops on startup

Well, I got back in town and put the 1050 on the bench. I pulled the transistors that were installed incorrectly because of the afforementioned list error, changed the others between q5 and q13, flipped the switch and :banana: got the dancing banana. No pop on the switch, two strong, clear channels, and all functions are fine. Time to move on to my next ailing Pioneer. Thanks for all the help. Main lessons learned, carefully check data sheets on each transistor for correct lead assignment, double check with diode function on meter. Verify the many helpful but informal parts lists posted on the internet.

It's peanut butter jelly time!
 
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