sx 1050 pops on start up

1050 pops

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
 
steamwhistle said:
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
Click to expand...


WE are SO not understanding each other - you said
voltage on 16 was 64.6
Click to expand...
and
Pin 2 = 78 volts
Click to expand...

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!!!
 
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1050 pops

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.
 
steamwhistle said:
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.
Click to expand...

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.
 
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.
 
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
 
1050 pops

Checking the power supply board and noticed replacement q9 is on a heat sink with no insulator. Is this correct?
 
Thanks for the thread Steamwhistle. :thmbsp:

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
 
1050 pops

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.
 
Yeah, I'm doing three amps at a time on this recap/cleaning thing. Two Pioneers, which have always been thick and clean sounding, and a Kenwood KA-2002 which always sounded decent but had an annoying amount of hiss and background noise. After reading a bunch here it sounded like transistors were indeed a good suspect in that area, so I tracked down as many substitutes as I could on them. Hopefully, that Kenwood isn't just hissy by nature and that'll clean some of it up. I was too young to remember what it sounded like new. Looking forward to my parts order Friday.

Take Care (and sorry for dragging this off topic :sigh:)

George
 
Jidis said:
Thanks for the thread Steamwhistle. :thmbsp:

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
Click to expand...

THAT is a classic burned up power switch - capacitors won't help, neither will deoxit - the switch has to be disassembled and the burned material burnished away. It is the same as in the sx-550 and sx-650, of which there are threads with pictures to guide you - there IS a fair amount of mechanical disassembly to get to and open the switch.

Yes, You should start your own thread, rather than confusing things in THIS repair thread.
 
steamwhistle said:
Checking the power supply board and noticed replacement q9 is on a heat sink with no insulator. Is this correct?
Click to expand...

No, unless the heatsink is isolated from everything else, then it's possible. Otherwise I will need to check a 1050 to see if that was the way it is done.
The collector would be hot at the 24v raw DC potential.

Is there 60v and 30v?

Turn it on, and measure all the voltages I mentioned. Sooner or later the resistor gets it's value lowered, and after 60 & 30 are present, the wires to the pins can be reconnected.

Sometimes the heatsink / transistor mount can fool you, they have an insulated threaded nut on the opposite side.
 
1050 pops

Thanks

pin 15 = 30.8
pin 16 = 60.2

q4 e=30.9, c= 60.3, b= 31.3
q1 b= 60.9, c=65.6, e= 60.3

next?
 
heatsink.jpg

Here's an image (I hope) of the heatsink on the 1050 power supply. The screw is metal on metal, and sink, transistor back, and collector have continuity. I now remember that when I took the old transistor off I didn't notice a mica insulator.
 
1050 pops

I re-attached pins13-17 and turned her on, leaving the 1000 ohm resistor at R1. Both relays kicked in, there was music. There was also a low hum in the speakers, and after a minute I felt R1 and it was pretty warm, maybe 140 f as a guess, so I cut power off. Should I replace the 1000 ohm resistor with the correct one at this point, or is the heat and the hum indicative of trouble somewhere?
 
steamwhistle said:
I re-attached pins13-17 and turned her on, leaving the 1000 ohm resistor at R1. Both relays kicked in, there was music. There was also a low hum in the speakers, and after a minute I felt R1 and it was pretty warm, maybe 140 f as a guess, so I cut power off. Should I replace the 1000 ohm resistor with the correct one at this point, or is the heat and the hum indicative of trouble somewhere?
Click to expand...

Go back to the original value - it's the same as putting a kink in the garden hose to stop a leak - once you fix the leak - go back to full strength.
 
steamwhistle said:
View attachment 177780

Here's an image (I hope) of the heatsink on the 1050 power supply. The screw is metal on metal, and sink, transistor back, and collector have continuity. I now remember that when I took the old transistor off I didn't notice a mica insulator.
Click to expand...

PIONEER intended that type of heat sink to be energized. Two on the same heatsink energized would not be as likely. That style of heat sink is found in many places in many models.
 
1050 pops

Put in the 10 ohm resistor, same wattage as original. Everything seems to work, but there is a low hum in both speakers. None of the controls eliminate it.
 
steamwhistle said:
Put in the 10 ohm resistor, same wattage as original. Everything seems to work, but there is a low hum in both speakers. None of the controls eliminate it.
Click to expand...

Check Fu1 & Fu2 on the AWR-104 board. One can pop and still the thing will limp along. Burning up a 10 ohm 1 watt resistor is a pretty good excuse to pop a fuse.

After that the 4 diodes D2, D3, D4 & D6 are suspect. They are 200v 1 amp diodes. 1n4004's will work fine (1n4003 through 1n4007 actually will work fine)

512-1n4004 conventional rectifier 1a 400v $0.06 ea

but there should be something like that yet at Radio Shack.
 
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