toymanmsp
Active Member
Pin 7 on the power supply board AWR-011 is reading OL - OL is incorrect. It's reading 19dvc.
Pioneer SX-727 - Relay Issues
- Thread starter toymanmsp
- Start date
Pin 7 on the power supply board AWR-011 is reading OL - OL is incorrect. It's reading 19dvc.
toymanmsp
Active Member
She's reading +46vdc
merlynski
Curmudgeon Electronicist
Remeasure the voltage on pin 7:
Power supply problem in that area, broken wire to pin 8, bad solder on the pin . . .
EDIT: add quote
Last edited:
toymanmsp
Active Member
toymanmsp
Active Member
still measuring 19vdc on pin 7. I'll take a look at the pins and solders on that part of the pcb.
toymanmsp
Active Member
Ok, I'll replace Q1, Q2, Q3, and D6. Should I measure R1 when I can pull the resistor when I'm replacing the other components or should this be done in the circuit? I'll get the transistors and diode replaced. I'm pretty sure that I have replacements and should be able to do this tonight.
merlynski
Curmudgeon Electronicist
It is always better to lift one end to measure a resistor, but really low value ones can sometimes be satisfactorily measured in circuit. IF you measure it while Q1 is out you are more likely to get a closer to correct reading. Note that nothing in a circuit will make a resistor read higher than its true resistance.
toymanmsp
Active Member
Well, still no relay click at startup. The resistor read 10.3 ohms with Q1 and Q2 pulled. After this, I replaced Q1, Q2, Q3, and D6. I believe that I have the pinouts correct, looked at them enough times. I used the dbt first to make sure that there were no larger issues. The bulb lit and quickly died down. I moved to the AC line and in both cases, the relay is not clicking at startup.
Here are some measurements that I took.
Pin 12: 26.79acv
Pin 13: 26.79acv
Pin 14: 34vdc
Pin 15: -34vdc
C1: 34 vdc
C2: -34vdc
Q1 Collector 47
Q1 Base 6
Q2 Base 2
D6 cathode 2
I hope that the measurements help. Let me know what's next. Thanks a million for your help.
toymanmsp
Active Member
Good morning! I figured that the values weren't good.
+C7 = 9vdc
I replaced Q1 with a KSC2073, Q2 with KSC2383 (this was recommended), but I changed Q2 to a KSC1845 per your message this morning. I incorrectly installed the wrong diode last night (it was late when I was working on the unit). I have since replaced this with what should be the proper 13v zener diode.
Some measurements:
Pin 12 and Pin 13: +26vac
Pin 14 +33vdc
Pin 15 -33vdc
C1 +33vdc
C2 -34vdc
Q1 Collector 46vdc
Q1 Base 6vdc
Q2 Base 2vdc
D6 Cathode 2vdc
Additionally, I think that one of the protection fuses blew, an arc or a flash of light coming from the middle fuse. I can see the filament on the top and the bottom, but am having a hard time seeing the middle filament. It's possible that it is there, but it does appear that one end is in the middle of the fuse and the other is bent downwards. Again, I'm not sure. I'd need to remove the silicone tubing from the fuse to be sure. I believe it was Pin 7 or Pin 8 when the fuse blew. I did measure both Pin 7 and Pin 8 this morning; Pin 7 6vdc / Pin 8 46vdc.
Thanks.
merlynski
Curmudgeon Electronicist
There are places a KSC2383 is better than a KSC1845 but this is not one of them. The KSC1845 has higher gain for better response in that application in a voltage regulator.
Lift one end and measure the resistors R2, R3, R4 on that board.
Fuses should be checked with your ohmmeter, unsolder one end (or the wire to it) because the transformer winding can fool you into thinking it is not open, when it really is. Mouser sells fuses with tails on them, or you can add a fuse holder.
Have you replaced C7 and C6?
Lift one end and measure the resistors R2, R3, R4 on that board.
Fuses should be checked with your ohmmeter, unsolder one end (or the wire to it) because the transformer winding can fool you into thinking it is not open, when it really is. Mouser sells fuses with tails on them, or you can add a fuse holder.
Have you replaced C7 and C6?
toymanmsp
Active Member
So is it fair to say that with the higher gain KSC1845 it is best for use with power supply related boards? Where would the KSC2383 be more appropriate? I ask I've used the KSC2383 for other Q's on the protection board. I will measure the resistors R2-4 on the board, hopefully later this evening.
Regarding the fuses, should I be concerned with the rubber tubing around the fuse when unsoldering? I'm guessing that there is a specific reason that they are there. If the fuse is blown, wouldn't that create additional problems or is it systemic from the issue you're helping to fix?
Good to know that mouser sells the fuses with tails. I'd probably prefer to add a fuse holder, but I'm not sure where to start with that. One thing at a time. No, I haven't replaced either C6 or C7. If I'm understanding the schematic these are two of the three hanging caps on the bottom side of the receiver, C6 is 220/10 and C7 330/16? Also, should these remain the same value, or can the voltage increase slightly?
I'm also planning to replace C1, C2, and C3 before this is all over, as I already have them in hand.
Also, what is your opinion on whether I should also plan to recap the AWK-010 AF board and the AWH-011 Power amp board? I had planned to stop with PSU, Phono, and the Protection boards, but I've read that the little blue Sanyo's should be replaced?
Also, I haven't forgotten the golden rule to fix one thing before you move onto another.
Thanks for your continued direction.
Regarding the fuses, should I be concerned with the rubber tubing around the fuse when unsoldering? I'm guessing that there is a specific reason that they are there. If the fuse is blown, wouldn't that create additional problems or is it systemic from the issue you're helping to fix?
Good to know that mouser sells the fuses with tails. I'd probably prefer to add a fuse holder, but I'm not sure where to start with that. One thing at a time. No, I haven't replaced either C6 or C7. If I'm understanding the schematic these are two of the three hanging caps on the bottom side of the receiver, C6 is 220/10 and C7 330/16? Also, should these remain the same value, or can the voltage increase slightly?
I'm also planning to replace C1, C2, and C3 before this is all over, as I already have them in hand.
Also, what is your opinion on whether I should also plan to recap the AWK-010 AF board and the AWH-011 Power amp board? I had planned to stop with PSU, Phono, and the Protection boards, but I've read that the little blue Sanyo's should be replaced?
Also, I haven't forgotten the golden rule to fix one thing before you move onto another.
Thanks for your continued direction.
merlynski
Curmudgeon Electronicist
I would not use that suggestion as a blanket statement. I follow the suggestions of the more long term experienced tech guys (MTF, echowars, mattsd, and others) but it is always a good idea to compare the application and datasheets, rather than just blindly following posted BOMs.
The KSC1845 is better where gain is more important than max collector current, compared to the KSC2383. (Fairchild/On datasheets)
KSC1845 has typical hFE1 of 580, hFE2 of 600, but a max collector current of 50mA.
KSC2383 has hFE of 60 minimum, and 320 maximum, and a max collector current of 1A.
On the AWR-011 power supply Q2 is the voltage regulation transistor, getting its input from voltage divider R5 & R6, inverting it (negative feedback) and applying it to the base of Q1, correcting voltage errors. Q1 provides the current gain to drive the load. Q2 does not need a high current capability, but the higher gain produces better voltage regulation.
The KSC2383 has a larger die, and can handle more current (power dissipation). It is a better choice for locations like Q6 on the Protection circuit (AWM-011), where its job is to dump the charge on C5 through R22 when the Protection circuit is triggered by a failure. Here current handling is more important than raw speed. The base of Q7 rises up to about +8.5vdc when the relay is pulled in, charging the cap to that voltage. When a fault is detected and Q5 is turned on the potential max current flow is 8.5v/22Ω = 386mA. This is way above what a KSC1845 is designed to handle, but well within the capability of a KSC2383.
FWIW, this is an expanded description of guidance from markthefixer's explanation to me of why a KSC2383 is a better choice for Q6 than a KSC1845.
IMHO, the tubing around the fuses is insulation you can see through, cheaper than a fuse holder (for the manufacturer) for fuses never intended to be easily or frequently replaced. I would get something like this to put in its place:
The C6 and C7 I was referring to are the 100µF/50v caps on the AWR-011 voltage regulator.
When I was planning the refurb of my SX-1050 I was originally going to replace only the 'shoot on sight' transistors and caps. Once I got into the project (read more posts) and saw how much work it was to get to the pcbs, and the relatives low cost and potential great benefits I decided to replace all the transistors with modern ones (upgrades where beneficial) , and all the electrolytic caps. I put film caps in for all the signal path electrolytics. These were 10µF and under. Power supply decoupling caps on individual boards were replace with new electrolytics. Many of these ended up with higher voltages. Except for the big main power supply caps (50% increase) I went with original capacitance values. FWIW, the opinions I have seen about the blue Sanyo 'capsistors' they are in the 'search and destroy'
category, not just 'shoot on sight.'.The power supply and protection boards will have little effect on the sound quality (potential
opinion), whereas rebuilding the AF and power amp section have great potential for improving (or restoring) sound quality.WHEW, another long-winded merlynski post
.
toymanmsp
Active Member
I would not use that suggestion as a blanket statement. I follow the suggestions of the more long term experienced tech guys (MTF, echowars, mattsd, and others) but it is always a good idea to compare the application and datasheets, rather than just blindly following posted BOMs.
The KSC1845 is better where gain is more important than max collector current, compared to the KSC2383. (Fairchild/On datasheets)
KSC1845 has typical hFE1 of 580, hFE2 of 600, but a max collector current of 50mA.
KSC2383 has hFE of 60 minimum, and 320 maximum, and a max collector current of 1A.
On the AWR-011 power supply Q2 is the voltage regulation transistor, getting its input from voltage divider R5 & R6, inverting it (negative feedback) and applying it to the base of Q1, correcting voltage errors. Q1 provides the current gain to drive the load. Q2 does not need a high current capability, but the higher gain produces better voltage regulation.
The KSC2383 has a larger die, and can handle more current (power dissipation). It is a better choice for locations like Q6 on the Protection circuit (AWM-011), where its job is to dump the charge on C5 through R22 when the Protection circuit is triggered by a failure. Here current handling is more important than raw speed. The base of Q7 rises up to about +8.5vdc when the relay is pulled in, charging the cap to that voltage. When a fault is detected and Q5 is turned on the potential max current flow is 8.5v/22Ω = 386mA. This is way above what a KSC1845 is designed to handle, but well within the capability of a KSC2383.
FWIW, this is an expanded description of guidance from markthefixer's explanation to me of why a KSC2383 is a better choice for Q6 than a KSC1845.
IMHO, the tubing around the fuses is insulation you can see through, cheaper than a fuse holder (for the manufacturer) for fuses never intended to be easily or frequently replaced. I would get something like this to put in its place:
View attachment 2025605
The C6 and C7 I was referring to are the 100µF/50v caps on the AWR-011 voltage regulator.
When I was planning the refurb of my SX-1050 I was originally going to replace only the 'shoot on sight' transistors and caps. Once I got into the project (read more posts) and saw how much work it was to get to the pcbs, and the relatives low cost and potential great benefits I decided to replace all the transistors with modern ones (upgrades where beneficial) , and all the electrolytic caps. I put film caps in for all the signal path electrolytics. These were 10µF and under. Power supply decoupling caps on individual boards were replace with new electrolytics. Many of these ended up with higher voltages. Except for the big main power supply caps (50% increase) I went with original capacitance values. FWIW, the opinions I have seen about the blue Sanyo 'capsistors' they are in the 'search and destroy' View attachment 2025625category, not just 'shoot on sight.'.
The power supply and protection boards will have little effect on the sound quality (potential View attachment 2025627opinion), whereas rebuilding the AF and power amp section have great potential for improving (or restoring) sound quality.
WHEW, another long-winded merlynski post
Good morning merlynski, many thanks for the detailed explanation regarding the KSC2382 & KSC1845 transistors. Quite helpful, as it is helping me to better understand what I need to learn!!! Thanks for your suggestion on a replacement for the fuses. Is what you suggested available on mouser? I'll also check the site to see what I can find. I haven't had a chance to pull the resistors yet. I'll also cut into the insulation around one end of the fuse to help desolder one end to get the meter leads onto the ends of the fuse. Regarding, C6 and C7 on AWR-011, yes, all electrolytics have been replaced on the board. I've also replaced diodes D1-D4, along with the transistors and small zener that you are aware of. I love the phrase 'search and destroy' about the Sanyo's. I will plan to also redo both the AF and the Power Amp sections as well. I went thru the boards, yesterday and I already have the capacitors on hand for both boards (Wima's for the lower value and Nichicon & Panasonic for the remainders) and believe that I have all the transistors as well, but will need to confirm that I have the right values to replace. It's my understanding that it's best to replace the known transistors that get noisy vs. replacing all of them? Also, are there other diodes, etc. that you would recommend changing as well? As you indicated, once you get into the project, you might as well go all in. I also have an SX-939 (along with several other receivers, Pioneer, Sansui, and Marantz) which I'm planning to refurbish as well. I recognize that these are all significant projects once you get into them. They should help to occupy me this winter.
Thanks again for the detailed post! I wouldn't say it's a long-winded post, I would say it's very informative and to the point. I'll report back soon.
merlynski
Curmudgeon Electronicist
I think 'Best' is a judgement call. Replacing known high failure components is the first priority, but some transistors that are not on the list can suffer from just being old technology, gain failing from use (2SC1384 as a relay driver) or 'black leg disease' - corrosion creeping up the legs into the transistor package or 'tin whiskers' growing inside the case, eventually causing a short, etc. Electrolytics drying out (in general). The more posts I read (not just on AK) the better I liked doing a good refurbishment. I don't replace signal/switching diodes or resistors unless they have failed. Inductors are probably the most reliable components (unless you break an adjustment core). Pots are the most problematic non-semiconductor component, and hardest to repair, but easy to replace. Switches (proprietary) are the hardest to replace but can be cleaned with Deoxit and exercise, or careful disassembly and cleaning.
So, after all that musing, I did replace all the transistors (except tuner and PS FETs) in my SX-1050.
The fuse holder picture came from Amazon, that style is readily available from many sources, just be sure to get one rated for the voltage or higher than it will be used at.
I've only restored two receivers (an SX-434 and an SX-636) so I'm no expert, but on both I decided to replace all the transistors (except for the tuner board), just for reliability and peace of mind.
Both receivers ended up sounding stunningly good in my opinion, and I'm glad I replaced all of the transistors. I don't think they lost any characteristic 70s warm sound at all. I picture them sounding the way they did when new 50 yrs ago, maybe even better? I guess it's controversial though. I think transistors get flaky and noisy and cause weird hard-to-find problems, so to me the risk of changing from original is outweighed by having a super reliable receiver for a long time to come. Especially since I tend to give mine away and I dont' want someone else to have weird issues.
Both receivers ended up sounding stunningly good in my opinion, and I'm glad I replaced all of the transistors. I don't think they lost any characteristic 70s warm sound at all. I picture them sounding the way they did when new 50 yrs ago, maybe even better? I guess it's controversial though. I think transistors get flaky and noisy and cause weird hard-to-find problems, so to me the risk of changing from original is outweighed by having a super reliable receiver for a long time to come. Especially since I tend to give mine away and I dont' want someone else to have weird issues.