sx 1050 pops on start up

[markthefixer]

Several things:

one, post the parts list you are working from
two, read and post the voltages on pins 16 & 15
three, turn it off and wait. the voltage on pin 15 should be about half of pin 16's 60 volts.

if q3 went in bad or something, q1, q2, q3 & D1(especially) are now all suspect.

it's hard to say what went wrong, nobody was watching or filming what was done.. it's all water under the bridge now anyways......

[steamwhistle]

Here she goes:
here's an update of an old post, with all the parts to do an entire rebuild, prices are probably a bit off, it's old:

sx-1050 power supply
q1 2sd313 to-220 bce npn 60v 3a 30w 5mhz
replacement part # 512-ksc2073tu_q @ $0.53 ea (bce, same layout) 150v 1.5a 25w 4mhz
q2, q3 2sc869 to-92 bce npn 50v 30mA .2w 150mhz
replacement part # 512-KSC2310YBU @ $0.11 ea (ecb, opposite layout) 150v .05a 0.8w 100mhz
q4 2sc1318 to-92 ecb npn 50v .5a .6w 200mhz
replacement part # 512-KSC2690AYSTU to-126 (ecb to ecb, same layout, different case) 120/a160 1.2a 20w 155mhz 35-320hfe $0.40
q5 2sb507 to-220 bce pnp 60v 3a 30w 5mhz
replacement part # 512-KSA940TU_Q @ $0.54 ea (bce, same layout) 150v 1.5a 25w 4mhz
q6,q7 2sa628 to-92 ??? pnp 25v .1a .15w 100mhz
replacement part # 512-ksa733clta @ $0.05 ea (ebc layout) 50v .150a .250w 180mhz
q8 2sa720 to-92 ecb pnp 60v .5a .625w 200mhz
replacement part # 512-KSA1220AYS to-126 (ecb to ecb, same layout, different case) 120/a160 1.2a 20w 155mhz 35-320hfe $0.39
q9,q12 2sd325 to-220 bce npn 35v 3a 10w 8mhz
replacement part # 512-ksc2073tu_q @ $0.53 ea (bce, same layout) 150v 1.5a 25w 4mhz
q10,q11,q13 2sc945 to-92 ecb npn 50v .1A .25w 150mhz
replacement part # 512-ksc945clta @ $0.06 ea (ecb to ebc, different layout) 50v .150a .250w 180mhz

d1 wz-140 mouser.com part # 512-1n5244b @ $0.04 ea
d2 wz-130 mouser.com part # 512-1n5243b @ $0.04 ea
d3,d4 wz-140 mouser.com part # 512-1n5234b @ $0.04 ea

c1,c9 220uF 80v mouser.com part # 647-UHE2A221MHD 220uf/100v $1.48ea
c3,c12 47uF 16v mouser.com part # 647-UPW1E470MDD 47uf/25v $0.31ea
c6,c14 47uF 35v mouser.com part # 647-UPW1H470MED 47uf/50v $0.34ea
c7 10uF 35v mouser.com part # 647-UPW1H100MDD 10uf/50v $0.25ea
c8 1uF 50v mouser.com part # 647-upw1h010mdd 1uf/50v $0.23ea
c15 100uF 35v mouser.com part # 647-UPW1H101MPD 100uf/50v $0.50ea
c16 220uF 25v mouser.com part # 647-UPW1V221MPD 220uf/35v $0.56ea
c17 47uF 10v mouser.com part # 647-UPW1E470MDD 47uf/25v $0.31ea
c20 100uF 25v mouser.com part # 647-UPW1V101MPD 100uf/35v $0.15ea
c22 47uF 10v mouser.com part # 647-UPW1E470MDD 47uf/25v $0.31ea
c23 2.2uF 50v mouser.com part # 647-UPW1H2R2MDD 2.2uf/50v $0.23ea
c24 220uF 16v mouser.com part # 647-UPW1V221MPD 220uf/35v $0.56ea

Sharp eyes will notice that Q4 and Q8 have been substituted with transistors with different, larger cases. They can handle more power, and will not be straining even under reasonable overload conditions. They also have small enough leads that they will fit through the current holes. A final bonus is that there are no metal tabs exposed to short out accidentally, any heat sinks will not be electrically live, but will most likely NOT be needed on Q4 or Q8.

Also the voltage ranges of the electrolytic capacitors has been increased, most specified caps now have a 50 volt rating. The difference is just a few pennies at most and are better suited to survival under fault conditions as well.

mouser.com EZ buy BOM import tool data:
647-UHE2A221MHD
647-UPW1E470MDD
647-UPW1H470MED
647-UPW1H100MDD
647-upw1h010mdd
647-UPW1H101MPD
647-UPW1V221MPD
647-UPW1E470MDD
647-UPW1V101MPD
647-UPW1E470MDD
647-UPW1H2R2MDD
647-UPW1V221MPD
512-ksc2073tu_q
512-ksc2310YBU
512-ksc2310YBU
512-KSC2690AYSTU
512-KSA940TU_Q
512-ksa733clta
512-ksa733clta
512-KSA1220AYS
512-ksc2073tu_q
512-ksc2073tu_q
512-ksc945clta
512-ksc945clta
512-ksc945clta
512-1n5244b
512-1n5243b
512-1n5234b
512-1n5234b
__________________
voltage on 16 was 64.6
voltage on 15 was -2.16
turned off, when 16 dropped to 0, 15 read -13mv

I checked for shorts along the foil side of 15's track and found nothing. No bridging at solder points.

The trouble started when q3 went in. I used heat sinks on q3's legs while soldering. I did not shield a little 1000pf ceramic cap which shares a solder joint with q3.

[markthefixer]

well, this is interesting...

the pin 16 voltage of 64v is a bit high, but we don't know what it was originally since you never posted any "before" troubleshooting readings I am aware of.

the pin 15 voltage of -2v means Q4 is either destroyed, or it's base (or even the collector) is shorted to ground, and Q4 supplies most of the signal electronics, so no sound.

So first take and post readings from Q4's collector, base and emitter to see what it is being told to do by the circuit.

Then take and post readings of Q1's collector, base and emitter, as well as pin 2.

[steamwhistle]

Pin 2 = 78 volts. Few other pin readings make sense because the unit is in protection mode.

Q1

Pos to base, Neg to emitter =.584 v
Pos to base, Neg to collector = .581v
Neg to base, Pos to emitter = 1.054v
Neg to base, Pos to collector = .595v
Neg to emitter, Pos to collector = 1.002v

Q4 readings as above

.571
.567
climbs to 1.1 v, then opens
.898
.581

[markthefixer]

Originally Posted by steamwhistle

Pin 2 = 78 volts. Few other pin readings make sense because the unit is in protection mode.

Q1

Pos to base, Neg to emitter =.584 v
Pos to base, Neg to collector = .581v
Neg to base, Pos to emitter = 1.054v
Neg to base, Pos to collector = .595v
Neg to emitter, Pos to collector = 1.002v

Q4 readings as above

.571
.567
climbs to 1.1 v, then opens
.898
.581

sorry, my bad for not being explicit, the requested readings are voltage measurements made referenced to the chassis ground.
We have to sort out the power supply before moving on to the protection.

pin 2 says that the circuit is being fed properly.

This:

voltage on 16 was 64.6
voltage on 15 was -2.16
turned off, when 16 dropped to 0, 15 read -13mv

I checked for shorts along the foil side of 15's track and found nothing. No bridging at solder points.

The trouble started when q3 went in. I used heat sinks on q3's legs while soldering. I did not shield a little 1000pf ceramic cap which shares a solder joint with q3.

is the trouble point we are at

[steamwhistle]

No problem. The readings for Q4 are E= -34.7mv, C= 61mv, B= 4.3mv. The readings for Q1 are B= -34.9mv, C= .963v, E= -31.4mv

I don't know if there's any significance to this, but Q1 and Q12 originally had different transistors and the list gives them the same ones, ksc-2073tu_q

[markthefixer]

Originally Posted by steamwhistle

No problem. The readings for Q4 are E= -34.7mv, C= 61mv, B= 4.3mv. The readings for Q1 are B= -34.9mv, C= .963v, E= -31.4mv

I don't know if there's any significance to this, but Q1 and Q12 originally had different transistors and the list gives them the same ones, ksc-2073tu_q

WE are SO not understanding each other - you said

voltage on 16 was 64.6

and

Pin 2 = 78 volts

so I expected to see:
The readings for Q1 are B= 65.2v, C= 78v, E= 64.6v

and the q4 readings, especially the base.

PLUS Q1 is a POWER transistor, MOUNTED ON A HEATSINK, ON THE POWER SUPPLY AWR-103 BOARD.....

I am ONLY talking about the AWR-103 board until further notice!!! Please RE-READ my posts with that in mind!!!

[steamwhistle]

Yes, I am reading only the power supply transistors. Those are the readings I gave you, that is, q1, the power transistor on the heat sink on AWR 103 power supply board, readings taken transistor legs to chassis. Though there's 80 v on pin 2, pin 16 is now dead and protection circuit is open. Last night I shotgunned the board with everything on the list, including a new q4 and q3. Still no sound, protection open.

[markthefixer]

Originally Posted by steamwhistle

Yes, I am reading only the power supply transistors. Those are the readings I gave you, that is, q1, the power transistor on the heat sink on AWR 103 power supply board, readings taken transistor legs to chassis. Though there's 80 v on pin 2, pin 16 is now dead and protection circuit is open. Last night I shotgunned the board with everything on the list, including a new q4 and q3. Still no sound, protection open.

R1, 10 ohms 1 watt is open circuit - a bad overload will burn it up.

The overload must be found and fixed or R1 will pop again.

Substitute a 1000 ohm resistor and when the voltage comes up with pins 13, 14. 15, 16. 17 disconnected the short is cleared.

Look for solder bridges and way wrong assumptions about transistor lead arrangements.

[steamwhistle]

Not quite sure I understand the following statement.


Substitute a 1000 ohm resistor and when the voltage comes up with pins 13, 14. 15, 16. 17 disconnected the short is cleared.

I did check R1 and it is some messed up.

[markthefixer]

substituting in 1000 1000 ohms for the 1 ohm will keep any current load low through a short.

With the pins connected there will be too much power load and it will be hard to distinguish if there is a short.

Once the correct voltages are obtained, the 1 ohm resistor goes back in, and the wires get hooked back up to the pins.

I just plain don't trust what's going on, and want to limit the damage while things are being sorted out

[steamwhistle]

Okay, I installed the 1000 ohm resistor and disconnected 13 through 17. What's next?

[steamwhistle]

Checking the power supply board and noticed replacement q9 is on a heat sink with no insulator. Is this correct?

[Jidis]

Thanks for the thread Steamwhistle.

The SX-450 I'm working on does the exact same thing. You switch it on, it crackles a few times and the panel lights dim in sync with the noises, then it usually stabilizes and is fine. My cap order is set to arrive Friday. Hopefully, it'll just be them or a cold joint. Otherwise, it'll have to wait for order #2.

Hope you get yours going!

George

[steamwhistle]

Thanks. The 450 is a nice sounding unit. If recapping stops the problem, which it probably will, I'd stop there and not fool with transistors.