Pots are PV36P103C01B00 and PV36P101C01B00, which, seem to be same specs except 125 deg C instead of 150. My bad. Filter caps are 383LX223M080B092VS with posts, but, it would be easy to desolder. I did check the outputs, which, goat67 thought were ok. I also confirmed no shorts from the outputs to the heatsink. I can replace the transistors that were misinstalled, but, that will, obviously take some time and I will have to see if they are in stock too.
SX950 restoration issue
- Thread starter jboerger3
- Start date
goat67
Addicted Member
Those trimmers are correct you did install them ie the 100 ohm and 10K are in the correct locations?
Like I said lets pull the outputs. keep track of were they came from.
Can you tell me what transistors are installed on the power supply board? Were any of these installed backwards?
Like I said lets pull the outputs. keep track of were they came from.
Can you tell me what transistors are installed on the power supply board? Were any of these installed backwards?
merlynski
Curmudgeon Electronicist
Unless they were installed backwards you do not need to remove the caps. If they are/were powered up while installed backwards you will need to replace them, as they will have been damaged.
Transistors that are powered up while incorrectly installed cannot be trusted, they are like the walking dead. Also those wrongly installed close dc coupled transistors in circuits like power supply regulators and power amp output circuits often take out or damage other components, that will likely fail sooner or later. Those transistors are cheap compared to your time and the value of what you are working on, dump them.
With this power amp architecture most of the necessary troubleshooting can be done with the power transistors removed.
I suggest pulling the output transistors, then get the power supplies working correctly.
After the supplies are right, then move into fixing the power amp and protection circuit. Problems in the power amp can cause the protection circuit to stay in protection. They both have to be working correctly before you connect speakers again.
You have lots of work to do to get this repaired and singing again, but it CAN be done. Go step by step, and recheck your work before powering up. We have all installed transistors and caps incorrectly.
Transistors that are powered up while incorrectly installed cannot be trusted, they are like the walking dead. Also those wrongly installed close dc coupled transistors in circuits like power supply regulators and power amp output circuits often take out or damage other components, that will likely fail sooner or later. Those transistors are cheap compared to your time and the value of what you are working on, dump them.
With this power amp architecture most of the necessary troubleshooting can be done with the power transistors removed.
I suggest pulling the output transistors, then get the power supplies working correctly.
After the supplies are right, then move into fixing the power amp and protection circuit. Problems in the power amp can cause the protection circuit to stay in protection. They both have to be working correctly before you connect speakers again.
You have lots of work to do to get this repaired and singing again, but it CAN be done. Go step by step, and recheck your work before powering up. We have all installed transistors and caps incorrectly.
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Power board has:
Q1 KSC1845
Q2 A940
Q3 KSC2383
Q4 KSA1013
Q5 KSC2383
Q6 KSA1013
Q7 KSC2383
Q8 & Q9 C2073
Q10 KSC2383
All of the power board transistors were installed correctly. All replacements went in the same was as oem except for Q10. I will confirm the pots location and pull the outputs after dinner. Glad I used the pink pads instead of the grease and mica.
Q1 KSC1845
Q2 A940
Q3 KSC2383
Q4 KSA1013
Q5 KSC2383
Q6 KSA1013
Q7 KSC2383
Q8 & Q9 C2073
Q10 KSC2383
All of the power board transistors were installed correctly. All replacements went in the same was as oem except for Q10. I will confirm the pots location and pull the outputs after dinner. Glad I used the pink pads instead of the grease and mica.
I'll start finding replacements for the mucked up transistors. Caps should all be fine unless one of the transistors caused a problem. No discrepancies in board markings from how the oem parts were installed. And the new ones were put in one at a time. I'll wait to pull the outputs until the replacement transistors are installed. Caps are relatively cheap too. Given that I mucked up all the non-heat sinked transistors on the power amp board and four of the six on the phono board, any suggestions on caps that may be compromised? Trying to spread the load of that $7.99 shipping charge.
Power board has:
Q1 KSC1845
Q2 A940
Q3 KSC2383
Q4 KSA1013
Q5 KSC2383
Q6 KSA1013
Q7 KSC2383
Q8 & Q9 C2073
Q10 KSC2383
All of the power board transistors were installed correctly. All replacements went in the same was as oem except for Q10. I will confirm the pots location and pull the outputs after dinner. Glad I used the pink pads instead of the grease and mica.
I don't have any spares, although, I could reinstall the oem's, to test, until I get the new ones.
Q1 KSC1845
Q2 A940
Q3 KSC2383
Q4 KSA1013
Q5 KSC2383
Q6 KSA1013
Q7 KSC2383
Q8 & Q9 C2073
Q10 KSC2383
All of the power board transistors were installed correctly. All replacements went in the same was as oem except for Q10. I will confirm the pots location and pull the outputs after dinner. Glad I used the pink pads instead of the grease and mica.
I don't have any spares, although, I could reinstall the oem's, to test, until I get the new ones.
merlynski
Curmudgeon Electronicist
Be careful if you try to reuse the pink pads on the transistors, the soft material get crushed and thinned when installed and may not survive reuse.
Don't reinstall the OEMs, it it risks damage to pads and traces unnecessarily.
Most of the time the installed caps are not subjected to over-voltage or reverse voltage from failed transistors.
By Power Board do you mean the AWR-101 Power Supply Assy?
If so
Q1 should be a 512-ksc2073TU, the KSC1845 is way too wimpy for that job. Was that a typo?
Q3 would be better as a KSC1845, it higher gain and faster speed make it a better choice, but they are in short supply. If the KSC2383 works OK you can leave it.
Don't reinstall the OEMs, it it risks damage to pads and traces unnecessarily.
Most of the time the installed caps are not subjected to over-voltage or reverse voltage from failed transistors.
By Power Board do you mean the AWR-101 Power Supply Assy?
If so
Q1 should be a 512-ksc2073TU, the KSC1845 is way too wimpy for that job. Was that a typo?
Q3 would be better as a KSC1845, it higher gain and faster speed make it a better choice, but they are in short supply. If the KSC2383 works OK you can leave it.
goat67
Addicted Member
No need to replace caps they should be fine.
The board I am asking about is THE POWER SUPPLY BOARD the one with the fuses on it. AWR-101
merlynski
Curmudgeon Electronicist
You are welcome!
If you powered up with a KSC1845 in place of Q1 it has probably been over-stressed, it is only rated for 50mA, the KSC2073 is rated for 1.5A, 30 times as much current. Put a new transistor in place of Q1. If you do not have another KSC1845 leave the KSC2383 in place for Q3. Unless absolutely necessary do not move or reposition transistors, discard the used (damaged?) one and install new ones. Small signal transistors are IMHO the most electrically fragile component when exposed to conditions outside their specs. If you reuse a transistor you are asking for a failure after you put it back in service. For a 5¢ to 50¢ component is it really saving anything if you have to unhook your whole system to replace a component, and fix the possible damage it created when it failed. The power supply and power amp sections are the most stressed parts of the amp, and deserve good parts. Also, unsoldering and soldering is hard on the pads and traces, and should be minimized.
OK, I'll get off the soapbox now . . .
If you powered up with a KSC1845 in place of Q1 it has probably been over-stressed, it is only rated for 50mA, the KSC2073 is rated for 1.5A, 30 times as much current. Put a new transistor in place of Q1. If you do not have another KSC1845 leave the KSC2383 in place for Q3. Unless absolutely necessary do not move or reposition transistors, discard the used (damaged?) one and install new ones. Small signal transistors are IMHO the most electrically fragile component when exposed to conditions outside their specs. If you reuse a transistor you are asking for a failure after you put it back in service. For a 5¢ to 50¢ component is it really saving anything if you have to unhook your whole system to replace a component, and fix the possible damage it created when it failed. The power supply and power amp sections are the most stressed parts of the amp, and deserve good parts. Also, unsoldering and soldering is hard on the pads and traces, and should be minimized.
OK, I'll get off the soapbox now . . .
I received the last of my transistors today. I have replaced any that may, at some point, have been installed incorrectly. And I verified the position of every transistor, that I had touched, against the board markings. I now have a small storehouse of transistors for this unit. The bulb dimmed very low and the protection relay (which I also replaced with a two contact unit) clicked! I took the following measurements on the power supply board:
Pin 1 SB 0 vdc 0
Pin 2 SB 5.4 vdc 16.02
Pin 3 SB 5.4 vdc 16.02
Pin 4 SB 13.9 vdc 12.66
Pin 5 SB 13.9 vdc 12.69
Pin 6 SB 51.5 vdc 48.45
Pin 7 SB 51.5 vdc 48.46
Pin 8 SB 36.5 vdc 34.74
Pin 9 SB 36.5 vdc 34.75
Pin 10 SB 36.5 vdc 34.76
Pin 11 SB 28.0 vdc 26.81
Pin 12 SB 0 vdc 0
Pin 13 SB -13.5 vdc -13.3
Pin 14 SB -51.5 vdc -50.84
Pin 15 SB -19 vdc -18.85
Pin 22 7.5 vac 6.99
Pin 23 7.5 vac 6.89
Pin 29 7.5 vac 7.0
I did not remove the outputs as I didn't want to compromise the pink pads. I figure if I had cooked the outputs, I will replace them, and the pink pads - if needed, after doing more testing and knowing it is safe to replace them. I had previously confirmed that the outputs were not shorted to the heatsink.
It appears that the voltage #'s are getting closer to spec. Are they low because of the dim bulb? I measured 107v a/c at the a/c power-in buss (where the power cord attaches inside the chassis). Should I be concerned with higher voltage at pins 2 & 3? I looks like they connect to the phono 2 switch. That switch, along with all the others on the front of the unit were disengaged when I tested the pins.
I don't want to jump the gun. Am I ready to take it off the dim bulb and set the offset and bios on the power amp board?
Pin 1 SB 0 vdc 0
Pin 2 SB 5.4 vdc 16.02
Pin 3 SB 5.4 vdc 16.02
Pin 4 SB 13.9 vdc 12.66
Pin 5 SB 13.9 vdc 12.69
Pin 6 SB 51.5 vdc 48.45
Pin 7 SB 51.5 vdc 48.46
Pin 8 SB 36.5 vdc 34.74
Pin 9 SB 36.5 vdc 34.75
Pin 10 SB 36.5 vdc 34.76
Pin 11 SB 28.0 vdc 26.81
Pin 12 SB 0 vdc 0
Pin 13 SB -13.5 vdc -13.3
Pin 14 SB -51.5 vdc -50.84
Pin 15 SB -19 vdc -18.85
Pin 22 7.5 vac 6.99
Pin 23 7.5 vac 6.89
Pin 29 7.5 vac 7.0
I did not remove the outputs as I didn't want to compromise the pink pads. I figure if I had cooked the outputs, I will replace them, and the pink pads - if needed, after doing more testing and knowing it is safe to replace them. I had previously confirmed that the outputs were not shorted to the heatsink.
It appears that the voltage #'s are getting closer to spec. Are they low because of the dim bulb? I measured 107v a/c at the a/c power-in buss (where the power cord attaches inside the chassis). Should I be concerned with higher voltage at pins 2 & 3? I looks like they connect to the phono 2 switch. That switch, along with all the others on the front of the unit were disengaged when I tested the pins.
I don't want to jump the gun. Am I ready to take it off the dim bulb and set the offset and bios on the power amp board?
merlynski
Curmudgeon Electronicist
Yes, they are low because the dim bulb is doing its job, strangling the input power.
Yes the 16v where it should be 5.4v in concerning, it means Q9 is probably shorted, or there is another failure in that ripple killer/regulator circuit. Test or replace Q9, Q10. It is a lighting circuit, so it may blow a bunch of light bulbs. The 'big' risk is popping the HA1196 chip (pin 9) for the FM stereo indicator lamp. Need to get that fixed first, then go off the dim bulb.
I can look at this some more tomorrow if you have not resolved it.
EDIT: correct Q3 to Q9
Yes the 16v where it should be 5.4v in concerning, it means Q9 is probably shorted, or there is another failure in that ripple killer/regulator circuit. Test or replace Q9, Q10. It is a lighting circuit, so it may blow a bunch of light bulbs. The 'big' risk is popping the HA1196 chip (pin 9) for the FM stereo indicator lamp. Need to get that fixed first, then go off the dim bulb.
I can look at this some more tomorrow if you have not resolved it.
EDIT: correct Q3 to Q9
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merlynski
Curmudgeon Electronicist
@jboerger3
I must apologize, I indicated Q3 in the previous post, it should have been Q9. My schematic was fuzzy and I misread the number. I have fixed the post and my schematic.
I must apologize, I indicated Q3 in the previous post, it should have been Q9. My schematic was fuzzy and I misread the number. I have fixed the post and my schematic.
Your new post (10:27) appeared as I was posting the above. I think Q9 should be a C2073? I have installed:
Q1, Q8,Q9 are C2073
Q2 is an A940
Q3 is a KSC1845
Q4, Q6 as KSA1013
Q5, Q7, Q10 as KSC2383
Should I change Q3 back to KSC2383?
My schematic is fuzzy too.