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SX 950 power board issues, and issues down stream

merlynski said:
First cover all but the very point of your probe with heatshrink or tape so it won't do again what we have all done in the past :oops:.
Pull Q6, it could be loading the regulator, then 6-way test it. Leave it out for now. Did you order more? I buy small transistors by 100 lots, they cost less and are on hand when I blow them up.
I would say Q2 and Q4 toasted, and may have taken ZD12 (13v) with them. The emitter of Q4 should be higher, but the emitter has to come up for the current supply for it. Replace ZD12 if you have one.

"Protection relay does not release" Actually the Protection relay pulls in when the unit comes out of protection, either at power up or after a fault clears. It releases when going into protection or at power off.
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Thanks. I changed back to micro clips so I can not hit anything else.

I will see what I have in stock. I need more transistors. I changed q2 and q4 with new units. I need a new q6 and the zd if I do not have one.

Thanks.
 
merlynski said:
First cover all but the very point of your probe with heatshrink or tape so it won't do again what we have all done in the past :oops:.
Pull Q6, it could be loading the regulator, then 6-way test it. Leave it out for now. Did you order more? I buy small transistors by 100 lots, they cost less and are on hand when I blow them up.
I would say Q2 and Q4 toasted, and may have taken ZD12 (13v) with them. The emitter of Q4 should be higher, but the emitter has to come up for the current supply for it. Replace ZD12 if you have one.

"Protection relay does not release" Actually the Protection relay pulls in when the unit comes out of protection, either at power up or after a fault clears. It releases when going into protection or at power off.
Click to expand...
Quick question I am only showing zd1 and zd2 on the power supply board. Do you mean zd2?
 
Rathwine said:
Quick question I am only showing zd1 and zd2 on the power supply board. Do you mean zd2?
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On the full schematic the zener for the negative regulator Is labeled ZD12, on the small schematic in the SM you are probably seeing ZD2. I have seen that kind of discrepancy before.
 
merlynski said:
On the full schematic the zener for the negative regulator Is labeled ZD12, on the small schematic in the SM you are probably seeing ZD2. I have seen that kind of discrepancy before.
Click to expand...
ZD12 is passing current both ways so it is gone. I get .186 one way and .210 the other way using DC continuity test.

Q6 test as follows out of board
Collector to base .606
Emitter to base .603
Collector to base open
Collector to emitter open
Emitter to base open
Emitter to collector open
My testor shows hFE256
Vf 576mV

I need to order the diode, some more transistors in case. Anything else?
 
merlynski said:
Try this one instead, the are the same spec as the original and are $0.14 each (under $0.12 if you buy 10) instead of $1.55.
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I did not see a link or part number to try instead. mouser is not showing anything that cheap with 13V rating. Let me know. thanks, troy
 
merlynski said:
OOPS :oops:. I forgot to paste it in: 512-1N5243BTR
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I finished the protection board and the switch board. Stopping for now. I need to finish the power supply and see if the protection circuit works before I play with anything else. I would feel better knowing it is working at this point. Parts are due tomorrow.

Once I know we have good power I can start checking voltages elsewhere and then finish. I still have the rest of the time amp, flat amp, and power amp to do.
 
merlynski said:
On the full schematic the zener for the negative regulator Is labeled ZD12, on the small schematic in the SM you are probably seeing ZD2. I have seen that kind of discrepancy before.
Click to expand...
Crossed fingers. Replaced the power supply q6 and zd12, tested on DBT, voltages looked good. Went to full line voltage, DC offer on right is +.044v and 0 on left. Plugged in old computer speakers to test, seems ok. Ran for a bit more and moved up to 100.00 speakers (don't want to risk my JBL4410's yet), and it sounds good. Going to leave it on and running a while to make sure we have no temp issues. Voltages on power supply board as follows on full line.

2 6.7. Went to 7 when it warmed up
4. 13.43. Went to 13.9 when warm
6. 50.2. 52.4 when warm
8. 38 -- this started at 35 but climbed when the amp got warmer
11 27.7. Got up to 29 as it warmed up
13 -13.7. -14 when warm
14 -52.5. -52.8 when warm
15 --19.4. -19.6 when warm

The pop came back one we got up to temp, but I have not gotten to the power amp board yet.

The lights are rock solid. Temperature as follows using a touchless thermometer.

Q8--146F
Q9--142F
Q1--136F
Q2--138F

And once completely warmed up no pops for the last 45 min. At 60 min mark, got one bigger pop then 2 smaller ones.

Some of the voltages creeped up on me.

Should I just move on to the other boards? I still have tone amp, flat amp, and power amp to go.

Thanks again for all of the assistance. It sounds much better now.
 
I don't see any problem so far. I would keep going, the pops could be coming from almost any small signal transistor in the signal path.
 
merlynski said:
I don't see any problem so far. I would keep going, the pops could be coming from almost any small signal transistor in the signal path.
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Cool. I have a bunch more parts to change out. This thing really gets hot. And that was with a pretty small load. Good thing I am building a new stand for it to keep it in clear air.

Thanks a ton for the assistance.
 
merlynski said:
You are welcome!
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Ok so finally doing the power amp board. One channel had a1015gr2b transistors and the other had the 2sa726s ones I was expecting. Was surprised. I am guessing at some point there was a failure. To be honest not certain which ones had those I didn't take pics first .
 
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