Oh Dear...Ohh Boy....SX-1980..ME!!!

Was ist das :

1.teflon ins.
2.comp's
3.ops

To sum it up : you are right . FM is Fu*ked up , Lost one PA channel , decided to take out the other one , and PS are okay and The monster is working fine as Pre-Amp hooked to my lovely SPEC 4 and Klipsch KG4 .
 
Ins. = Teflon Insulated wire, but PVC will work okay
Comp's = components
OPS = Output stage = big TO-264 transistors (bjt)
Okay we add at tuner to the fix-it list too.
 
rcs, I interpret that the fault happened first, and upon disassembly the STV-4h diode wire fractured at the component body.

Omri - he is saying that you need to have LOTS of (extra) parts on hand - which does make sense comparing the parts costs versus the shipping costs.

6 way tests on transistors:
Bipolar Junction Transistor Testing Basics, formalized and rigorously defined in post #11


When we power up that amp channel again, we can just install one of three output transistors per triplet and not run the channel too hard until we are sure it is behaving.
edit: OOOOPPPPSSSS RCS16 said it first!!! credit given where credit due!!

I will not say more because I can't separate the email communications from the forum communications in my head.
especially with my head being so fuzzy right now.

Don't want to spill any personal confidential details that may have been in emails but not mentioned in forum.
But conversely, anything in my emails is "cat's out of the bag" and no secret...
 
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Mark your interpretation is Right. That what happened .
I will post the results of 6 way transistor check tomorrow.
Can I do the test when the transistors are all in place on the heatsink and wires together? Please say yes !! Lol
But before , I just want to say that I suspect that it was VR1 , Why?
When I was trying to adjust it , to reach 0V at the desired pins (can't remember I'm in bed no SM here-maybe 23,24?) , it would suddenly alter and go to +78V. Like it had a bad contact to I don't know defective way of going up&down with ohms.
 
6 Way transistor check :

Right channel :

PNP:
black lead to base, red lead to collector, result = 0.4658
black lead to base, red lead to emitter, result = 0.4918
red lead to base, black lead to collector, result = OL = No conduction
red lead to base, black lead to emitter, result = OL = No conduction
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction

NPN:
black lead to base, red lead to collector, result = OL = No conduction
black lead to base, red lead to emitter, result = OL = No conduction
red lead to base, black lead to collector, result = 0.4989
red lead to base, black lead to emitter, result = 0.5122
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction

Notes :
All checks are done when transistors are on heatsink.
Transistors are connected to each other


Left channel :
ALL PNP shorting .

NPN -
1 shorting .

the other 2 NPN's :

black lead to base, red lead to collector, result = OL = No conduction
black lead to base, red lead to emitter, result = OL = No conduction
red lead to base, black lead to collector, result = 0.4988
red lead to base, black lead to emitter, result = 0.5124
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction
 
I don't give up on this one :)
I had the time to rebuild the right channel amplifier board .
I connected the amplifier board to the 3+1 / 4+1 connectors from receiver.
OUTPUT transistors NOT CONNECTED to their sockets.

Service Manual Adjustments says :
Pin 17 (red probe) and Ground (Black probe) should give ZERO volts +/-30mV.
When trying to achieve that using VR1 - readings are not stable , the minimum I managed to get is 2.2V , and every once in a while it just jumps to 73.3V and kicks in and out protection .
I replaced VR1 and no luck.
 
1. you repaired the busted STV lead? epoxied it after soldering for strain relief?

I think one of the solder joints that were NOT touched by your rebuild is still acting up.

That would tend to be either the caps (unlikely to cause this problem) or the wire jumpers.

IF it were the glopped up board It remains highly likely that a trace somewhere on the board was damaged by the "glop removal" - I HAD intended a near - microscopic inspection of all the traces and an ohmmeter verification of each during my rebuilding process.

Right channel amplifier board?

I don't understand.

I thought the left channel was the original 109 board that came with the unit,
and the right channel was the glopped up 109 board that we were shoehorning into the 110 board's position.

So it is the UNGLOPPED board that failed.

R7(39k), R5(39k), Q1(120v), R9(39k), R103(120k), VR1(150k) are all suspect.

If R5/R7 divider is malfunctioning, the q1 collector is getting +80v instead of +40v and that may be pushing the transistor past it's breakdown voltage. Check Q1 collector's voltage - it SHOULD be +40v or half of the voltage at pin 2 which is the +80v regulated supply. It should NOT matter what VR1 is set at.

Adjust the 109 board to as close to 0.0v as you can, and read (power off) the resistance of VR1, R103 (if jumper b is cut) and R9.

Then watch the output voltage while the board is COMPLETELY stable, we want to see if it is vibration induced.
 
Right channel amplifier board is the glopped board and this is the board we are discussing (the original board is empty and aside)

1. Yes I repaired STV.
2. Reflowed ALL joints including the ones I didn't touch.
R7 = 39K
R5 = 39K
R9 = 39K
R103 = 2K (You maybe mistyped)
Vr1 = 150K is reachable.

Q1 collector = 28.8V - depends on VR1 location - Max is 32V and Min is 18V.

Additional tests I made :
R109 = 120K
R103 = 2K
R97 = 2K

All resistors were pulled one leg and checked.
Now , when making the same check as my previous post ,I get from PIN17 = -83.3V
 
so we have a blown up original 109 board and this is happening to the (formerly glopped up) transplant board?

with which outputs? left channel or right channel?
 
Yes mark that's the case
The original board was mounted on left channel as should . (Although boards are interchangeable )
The outputs of right channel are Ok. Left channel outputs few damaged .
To remind you I replaced all parts (except few you left on the glopped board and I kept as reference on the other board)
on both boards to keep similarity .
 
right channel (transplant 109) board with right channel output transistors, but outputs NOT connected RIGHT NOW?
 
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