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SX-1050 Blowing Fuses

mark, i spoke way too soon yesterday, i had this thing playing all night for 12 hours, when i got up i turned it off, put the bottom cover back on, and then flipped the switch back on and no secondary relay click...i took readings from the protection board(AWM-090) and the power supply board(AWR-103)

awm-090 protection board

1. 0v
2. 13.25v
3. 0v
4. .075v
5. .025v
6. .020v
7. -.032v
8. .050v
9. 0v
10. 0v
11. -.005v
12. 63.75V


awr-103 power supply

1. 24.8v
2. 81.0v
3. -83v
4. 0v
5. 13.5v
6. 13.5v
7. -13.30v
8. -60.80v
9. 30.95v
10. -25.20v
11. -25.20v
12. 0v
13. 26.05v
14. 26.05v
15. 32.27v
16. 68.85v
17. 65.80v
18. 54.50v
19. 54.50v
 
what do you think is going on, could it possibly have to do with putting the bottom cover on?
 
tsd71 said:
mark, i spoke way too soon yesterday, i had this thing playing all night for 12 hours, when i got up i turned it off, put the bottom cover back on, and then flipped the switch back on and no secondary relay click...i took readings from the protection board(AWM-090) and the power supply board(AWR-103)

awm-090 protection board

1. 0v
2. 13.25v sure this isn't negative 13.25 - which would be ok??
3. 0v this should be checked on AC volts, for 7.5v ac, DC won't read anything - are the main scale lamps working?
4. .075v
5. .025v
6. .020v
7. -.032v
8. .050v 50mv offset on the amp - try to adjust it later but no problem here.
9. 0v
10. 0v
11. -.005v 5mv offset on the amp, darn fine...
12. 63.75V


awr-103 power supply

1. 24.8v
2. 81.0v
3. -83v
4. 0v
5. 13.5v
6. 13.5v
7. -13.30v
8. -60.80v
9. 30.95v sure it isn't negative? You've gotten the other (8,10,11) polarities correct....
10. -25.20v
11. -25.20v
12. 0v
13. 26.05v
14. 26.05v
15. 32.27v
16. 68.85v a bit high, but acceptable..
17. 65.80v a bit high, but acceptable..
18. 54.50v I think ya slipped a decimal point there tex... :D or a miracle occurred.
19. 54.50v I think ya slipped a decimal point there tex... :D or a miracle occurred.
Click to expand...

So far, nothing glaring pops out, in fact no smoking guns, but some readings need to be rechecked, as indicated - hope you take the comments as intended, as in humor - NOT sarcasm... :D cuz this is a great post.

The main scale lamps run off the 7.5v ac transformer winding (blue wires), and the protection circuit senses that for turn on and turn off - while ALL the OTHER lamps run off of a DC power supply and wouldn't be affected by a blown FU5 (1.5 amps , blue wire, pins 1 & 15 on the awr-104 power supply board with all the fuses.
 
i take the comments as intended, i know where you are coming from...now to my mistakes

awr-103

9. -30.5v
16. 63v
17. 63v
18. 5.35v
19. 5.35v
 
tsd71 said:
i take the comments as intended, i know where you are coming from...now to my mistakes

awr-103

9. -30.5v
16. 63v
17. 63v
18. 5.35v
19. 5.35v
Click to expand...

awr-103 voltages look good

tsd71 said:
would this have anything to do with the lamps, two are bad
Click to expand...

If the other two scale lamps are working, no problem there. BUT what about:

markthefixer said:
awm-090 protection board

2. 13.25v sure this isn't negative 13.25 - which would be ok??
3. 0v this should be checked on AC volts, for 7.5v ac, DC won't read anything - are the main scale lamps working?
Click to expand...
 
We rebuilt the power supply, but did nothing with the protection board, correct?

Looks like the best bet is to replace C5 & C6, Q6 & Q7. Do you want to go looking for the mouser parts numbers (ztx1056 x 2) (2.2uf/50v, 47uF/50v & 2x 330uf/6v) or should I?

The 0.22 at 25v caps if electrolytic can be replaced with film caps.

You could read the voltage on both sides of R25 (2.4k) and Q7's e, b & c to dig deeper first if you wish.
 
do you think the protection board might be the culprit, aren't the rteadings pretty up to spec?
 
markthefixer said:
We rebuilt the power supply, but did nothing with the protection board, correct?

Looks like the best bet is to replace C5 & C6, Q6 & Q7. Do you want to go looking for the mouser parts numbers (ztx1056 x 2) (2.2uf/50v, 47uF/50v & 2x 330uf/6v) or should I?

The 0.22 at 25v caps if electrolytic can be replaced with film caps.

You could read the voltage on both sides of R25 (2.4k) and Q7's e, b & c to dig deeper first if you wish.
Click to expand...



no reading on r25
 
mark, i think i found something, while taking readings on q7, i was resting my finger on the relay when i pulled up the relay clicked in, tried it again with the same result, maybe loose and a resolder?
 
tsd71 said:
do you think the protection board might be the culprit, aren't the rteadings pretty up to spec?
Click to expand...

What's going IN is ok, but what is it doing with it. These transistors and caps ARE the first line of deterioration and repair.

Try soldering in the relay and Q7, but it may be the transistor itself as it has aged and been loaded.th
 
markthefixer said:
What's going IN is ok, but what is it doing with it. These transistors and caps ARE the first line of deterioration and repair.

Try soldering in the relay and Q7, but it may be the transistor itself as it has aged and been loaded.th
Click to expand...


Finally, resoldered Q7, and the relay, now music, or Quadrophenia by The Who, for all the kiddies here.....

Mark you are a huge asset to this site, I thank you again...

Maybe now on to the SX-1250 in the garage
 
markthefixer said:
Re:at the awm-090 protection circuit, possibly, D5 & R25 forms a 33v 500mW zener voltage regulator and if bad WOULD upset the protection circuit. look for 33v at the point between D5 and R25, referenced to ground.
That area will run hot, Q7 runs saturated, but a 120v 100ma 1w npn hi-gain transistor will do.
This is the best: (mouser.com part number)

..... relay driver ............
522-ZTX1056A NPN TO-92E ebc 150v 3a 1w (Vce(sat)=0.3v @ 3a) 120mhz 30-1200 hfe

IF the 33v zener diode is misbehaving, there is a slightly different fix. Other very accomplished people on this board don't replace the 33v diodes directly, but rather use a 16v and a 17v zener in series. It's a bit of a push at 33v, especially at that power, so 2 diodes are more stable.
Click to expand...

My Zener diode measures 35.4 volts and occasionally peaks at 36 volts. Does this mean that the diode is misbehaving?
 
backmd said:
My Zener diode measures 35.4 volts and occasionally peaks at 36 volts. Does this mean that the diode is misbehaving?
Click to expand...

In all likely hood yes, that is the first thing I would suspect and correct. There is even a service bulletin on that one.

But I wouldn't expect that to be the end of it in every case - so - swap in the two (16v & 17v 1/2 watt zeners) and then see if it settles down, if not, start a new thread - I'll surely see it here and you deserve your very own thread :D
 
markthefixer said:
In all likely hood yes, that is the first thing I would suspect and correct. There is even a service bulletin on that one.

But I wouldn't expect that to be the end of it in every case - so - swap in the two (16v & 17v 1/2 watt zeners) and then see if it settles down, if not, start a new thread - I'll surely see it here and you deserve your very own thread :D
Click to expand...

I can put in a 5 watt zener diode at 33 volts, would that be OK?
 
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