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No voltage on pins 8-19 on SX-1050 awr 103 board????!!!!

Get replacement transistors, spare transistors and the resistors (3.3k's).

We're not sure about the positive side regulator (even though the tests were ok, the operating results weren't) so get some extras (q1,q2,q3 they're cheap).

We haven't addessed Q13-Q20 on the amp board, no less the output transistors. I'll look into them later tonight.
 
Will Order Replacements Tonight. Extras Of Course!! Will Hold Off On Amp Transistors Untill We Get There Unless You Want Me To Order Them As Well.
 
Steve 1050 said:
Will Order Replacements Tonight. Extras Of Course!! Will Hold Off On Amp Transistors Untill We Get There Unless You Want Me To Order Them As Well.
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Here's my interim work on the subject:
power amp
q1-6 2sa750 to-92 ecb 50v 0.05a 0.25w 100mhz (512-KSA910YBU @ $0.11 ecb 150v .05a 0.8w 100mhz)
q7-10 2sc1439 to-92 ecb 150v .05a .5w 130mhz (512-ksc2310YBU @ $0.11 ecb 150v .05a 0.8w 100mhz)
q11,q12,q21,q22 2sa858 to-92 ecb 150v 0.05a 0.5w 100mhz hfe 150 min (512-KSA910YBU @ $0.11 ecb 150v .05a 0.8w 100mhz)
........
q13,q14 2sa858 to-92 ecb 150v 0.05a 0.5w 100mhz hfe 150 min (512-KSA910YBU @ $0.11 ecb 150v .05a 0.8w 100mhz)
q15,q16 2sc1439 to-92 ecb 150v 0.05a 0.5w 130mhz (512-ksc2310YBU @ $0.11 ecb 150v .05a 0.8w 100mhz)
q17,q18 2sb536 to-220 bce 120v 1.5a 20w 40mhz max hfe 250
512-ksa940otu_Q @ $0.54 ea (bce, same layout) 150v 1.5a 25w 4mhz
q19,q20 2sd381 to-220 bce 120v 1.5a 20w 40mhz max hfe 250
512-ksc2073tu_q @ $0.53 ea (bce, same layout) 150v 1.5a 25w 4mhz
q23,q24,q27,q28 2sb539 to-3 ebc 160v 15a 100w 8mhz max hfe 200
q25,q26,q29,q30 2sd287 to-3 ebc 160v 15a 100w 8mhz max hfe 200

wading through the details, q13,q14 = ksa910 (remember q6,q7??) q15,q16= ksc2310 (remember q2,q3??) q17,q18= ksa940 q19,q20= ksc2073.

I trust the ksa910 and ksa2310 numbers are familiar (and cheap) while the ksa940 and ksc2073's at 54 cents each aren't too bad...
 
Steve 1050 said:
HAVE BEEN BUSY STILL TRYING TO GET PARTS. should be getting them shortly.
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I wasn't worried.....time constraints.... budget constraints.... family..... home.... etc...

Just as a point of information, there are some things to do in the amplifier section before applying power, testing transistors etc...

I'm looking at shutting down (or fixing, depending) the final three sections of the amps if the transistors test bad... (pre-driver q13-16, driver q17-20, power outputs q23-30)
 
Steve 1050 said:
parts will arrive fri. will be taking mesurements and posting soon
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Be VERY CAREFUL!!!!!!! around the power amp board to heatsink connections, the wires to the power transistors are robust BUT the other components on the heatsinks are the VERY FRAGILE bias diodes, ONE per channel.

On the diagrams they are called varistors STV3H, D7 and D8 on the schematic.

The bias diode's wires go from the power amp board to the heatsink, and the diodes are darn near unobtainable ($$) if you break a wire.

DON'T flex them near the body of the diode where they could break off flush.

Best Idea is to carefully unscrew the mounts to the heatsink, and get the diodes into a safe position on the board.

We must be very careful about powering up the amp after anything is done in the bias area, this is where smoking ruins are generated if the circuit opens up / breaks in this current path.
 
There is nothing like the feeling of component level testing and diagnosing the problem replacing the part and what ever your fixing springs back to life.

My only regret is being stuck in a job where you test input test output replace board and walk away. I lost all my component level testing ability this way because you simply forget. The likes of Mark, Glen, Fred and a few others are bringing this all back to me.

Thanks guys.
 
Musicalme said:
There is nothing like the feeling of component level testing and diagnosing the problem replacing the part and what ever your fixing springs back to life.

My only regret is being stuck in a job where you test input test output replace board and walk away. I lost all my component level testing ability this way because you simply forget. The likes of Mark, Glen, Fred and a few others are bringing this all back to me.

Thanks guys.
Click to expand...

Component level diagnosis WILL be a lost art.

Contributing factors:
1) The high level of integration of functions in chips, the short half life of that chip's actual use in industry (before something better comes along), the investment in equipment needed to even replace a chip type resistor, capacitor, transistor or less complex integrated circuit that has failed
2) The investment (and more importantly THE WILL) needed to produce documentation adequate to the task of troubleshooting.
3) The actual cost of the equipment itself, versus replacement, and the parts cost IF replacement parts can even be found.

Have you looked at modern hard drives? The latest one I tore down was an old (1999) 20 GB which turned out to be a single head drive. The level of integration and the elegance of the implementation was both artful, simple and eminently NON-repairable... One board, highly integrated with few VLSI chips and almost NO other components. The lead pitch on the VLSI chips was so close that I expect that ONLY automatic placement equipment could get it close enough to work. Two "connectors" to the drive proper, the motor and the "data" which included the head positioner, which went through to the sealed area. On the head positioner arm was a flex type circuit that had an integrated circuit on it, which connected to the head(s).

FIX THAT?? Fuhgedaboudit......
 
I agree the repair of things electronic is a dying art. however as long as people still have a desire for "old" stereo equipment and the like it will survive. as long as there are still people who like to "build their own or try to improve an existing product I think it will survive.
 
Steve 1050 said:
I agree the repair of things electronic is a dying art. however as long as people still have a desire for "old" stereo equipment and the like it will survive. as long as there are still people who like to "build their own or try to improve an existing product I think it will survive.
Click to expand...

There is a science fiction story about a guy who became VERY important, because he could ADD NUMBERS without a machine, on PAPER... Nobody understood the old "legacy" code that did it.
 
Yippie! parts arrived today now for the next step. I'm going to dinner with my wife and then get back into repair mode.
 
I totally agree with you Mark. I work on converter and inverter drives for steel mill operations and yeah I'd hate to have to try to diagnose and replace parts on those boards. Pretty much the only components that need testing and changing are the big white hockey puck looking thingys ;)
Some boards are repairable but I get payed to keep them running not to spend wasted? time repairing boards. Those get sent back to the manufacturer and they are happy to pay him 20 times my salary to replace a bad diode or something. Such is life.
My reference was to what we are doing here and now and not the present/future of the electronics industry. I actually did all this stuff during my apprenticeship in a post trade course. We even touched on valves!
However its amazing what you forget when you don't do it regularly.

It truly is an art thats for sure. Regrets nahhh but I'm getting a kick out of following these threads and picking up little tid bits and thinking yeah I remember that now. :)
 
Mark , after removing wires to pins 8,16,17 and replacing all transistors on regulator board voltages are as follows:
Pin 1= 22.3
pin2=78.8
pin3=-54.6
pin4=0.0v
pin5=17.95
pin6=17.95
pin7=-12.3
pin8=-42.6
pin9=-18.7
pin10=-15.6
pin11=-15.6
pin12=0
pin13=24.96
pin14=25
pin15=31
pin16=61.5
pin17=61.5
pin18=14.6
pin19=14.6

we appear to be getting closer.
 
Well, we have to look at the OTHER power supply board, the one with the fuses on it. FU1 or FU2 could be blown or more likely D3 or D4 is blown, as the -54.7v on pin 3 is low.

Once we have the voltage on pin 3 down to -78 or so, then we will worry about the voltages on pins 7, 8 9, 10 & 11 if they aren't where they should be (they aren't right now but there are (D3, D4) extenuating circumstances.

D3 and D4 are 200 volt 1 amp diodes (plain jane 1n4003's or greater (4004,5,6,7,8)will do fine). Radio Shack part # 276-1102 @ 0.99 for 2.. a bit pricey, but better than waiting or postage.

Do the dmm diode test for both D3 and D4. One HAS to be bad...

Then BACK on the first, REGULATOR card, First carefully check the lead arrangements of Q9, Q10, Q11, Q12 & Q13 something is wrong...
Q9 2sd325 to-220 bce ksc2073 same layout
Q10 2sc945 ecb ksc945 eBC WARNING DIFFERENT LAYOUT, NOT REVERSED!!
Q11 2sc945 ecb ksc945 eBC WARNING DIFFERENT LAYOUT, NOT REVERSED!!
Q12 2sd325 to-220 bce ksc2073 same layout
Q13 2sc945 ecb ksc945 eBC WARNING DIFFERENT LAYOUT, NOT REVERSED!!

Then if there was no error found, read the voltage across the leads of D4, the pin 5&6 voltage should be 13v NOT almost 18 and pins 18,19 should be 5.4, NOT 14v FOURTEEN VOLTS WILL BURN OUT the speaker lamp and function lamp BULBS VERY QUICKLY!!!

So open up pins 5 & 6 & 18 & 19 before turning it back on.

If you found and corrected an error on the 2sc945's then leave the pins connected and test the voltages briefly. 18v instead of 13 isn't too disasterous, but 15 instead of 5 is BAAAD.
 
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