Pioneer SX-737 No Sound, No Relay Click, Lights On

pa_200 said:
Something is completely screwed up with your work.

I hope you have a spare SC945, so you can test again the pin out.
You have to find standard procedure how you identify transistors on your desk, how to find the correct pin out, install it on the board and recheck the pin out before you start soldering.

For me the only certain way is my standard step by step approach.

If there a different transistor types required, I always work with on type at a time. First get the right numbers, test at last one with the little transistor tester, print facing towards me AND write down the displayed pin out.
Recheck ones more that I have a NPN or PNP, if hFE and Uf is required as well. Only after that is confirmed, I adjust the legs to the board layout, and take my time to match the displayed pin out with the print on the board.

Last thing before I solder all three legs. Start with only one leg, then turn to the part side and try to position the transistor in a most favorable position, that you can easily read the numbers for a later test.

The picture below shows how I prepare the transistors, AND you can see, that the SC945 I have on my desk are ECB pin out with the flat side facing me.
I haven't seen a SC945 with a CEB pin out so far.
Click to expand...
I am embarrassed…again. I wrote it down on my package incorrectly after I did what you did and had it in my tester. I will change the out. Ugh
 
pa_200 said:
Something is completely screwed up with your work.

I hope you have a spare SC945, so you can test again the pin out.
You have to find standard procedure how you identify transistors on your desk, how to find the correct pin out, install it on the board and recheck the pin out before you start soldering.

For me the only certain way is my standard step by step approach.

If there a different transistor types required, I always work with one type at a time. First get the right numbers, test at last one with the little transistor tester, print facing towards me AND write down the displayed pin out.
Recheck ones more that I have a NPN or PNP, if hFE and Uf is required as well. Only after that is confirmed, I adjust the legs to the board layout, and take my time to match the displayed pin out with the print on the board.

Last thing before I solder all three legs. Start with only one leg, then turn to the part side and try to position the transistor in a most favorable position, that you can easily read the numbers for a later test.

The picture below shows how I prepare the transistors, AND you can see, that the SC945 I have on my desk are ECB pin out with the flat side facing me.
I haven't seen a SC945 with a CEB pin out so far.
Click to expand...
You my friend, are a very very patient detail oriented genius!! After switching those 3 ksc945’s to the proper pin placement, I now have a relay click! What would you suggest next!
 
I was on the verge of running out of ideas.

Next step should be, test again the protection voltage on all pins with the relays pulled in. And if you like, all other like the one from that post as well, just to confirm, that the transistors have the expected voltage.
G

Post in thread 'Pioneer SX-737 No Sound, No Relay Click, Lights On'

pa_200 said:
Sorry, but I like to see more voltages. Please use the list for a better overview.
And tell us, what parts you have changed already on the protection board.
Click to expand...
Numbers appear to be all over the place on some or most. See attached. Note that no parts have been removed or replaced on this board.

After that, recheck as well the pin out on AWF 011 with the same procedure. They look somewhat unusual, too.
If the protection board voltages are in spec, you can go to the DC and offset adjustment on the Power Amp, and report the numbers.

After that you should be able to plays some music, but use only a headset first, don’t risk expensive speakers unless your unit is fully restored and all work secured.
See you tomorrow
 
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pa_200 said:
I was on the verge of running out of ideas.

Next step should be, test again the protection voltage on all pins with the relays pulled in. And if you like, all other like the one from that post as well, just to confirm, that the transistors have the expected voltage.
G

Post in thread 'Pioneer SX-737 No Sound, No Relay Click, Lights On'

pa_200 said:
Sorry, but I like to see more voltages. Please use the list for a better overview.
And tell us, what parts you have changed already on the protection board.
Click to expand...
Numbers appear to be all over the place on some or most. See attached. Note that no parts have been removed or replaced on this board.

After that, recheck as well the pin out on AWF 011 with the same procedure. They look somewhat unusual, too.
If the protection board voltages are in spec, you can go to the DC and offset adjustment on the Power Amp, and report the numbers.

After that you should be able to plays some music, but use only a headset first, don’t risk expensive speakers unless your unit is fully restored and all work secured.
See you tomorrow
Click to expand...
I'll get the cap measurements tomorrow but here are the 025 voltages. Overall, much much better. Still not exact to your measurements.

Edit 20260304:
C5 minus was -4.5
C6 plus was 8.9
 

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golfnut said:
I'll get the cap measurements tomorrow but here are the 025 voltages. Overall, much much better. Still not exact to your measurements.
Click to expand...
Many a person has incorrectly installed replacement transistors. That is generally the culprit in no relay engagement. Do it once and you'll know what to check going forward.

Step one, get a stable power supply. Set voltages.
Step 2, only after that, work every board doing DBT after finishing each board before moving on.
 
Congratulations, finally all pin voltages on the protection board look good and are close enough to the original values.

Same with the transistor voltages, EXCEPT for the Q6 base to emitter voltage.
You can see, all other transistors have a difference between 0.6 and 0,7 Volts between B and E.
Q6 has a difference of 2.3 Volts between B (-1.6) and E (+0.7) but I’m not deep enough in that thematic to find or explain the reason for that big difference.
It could be the tolerance of your DMM, we can only hope, that one of the experts comes up with an idea.

And as long as it works, I would leave it that way. The only old parts left in that area are C5 and C6 and it won’t harm, if you replace them as well, together with the recommended fly-back diode between pins 9 (anode +) and 10 (cathode -).
 
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pa_200 said:
Congratulations, finally all pin voltages on the protection board look good and are close enough to the original values.

Same with the transistor voltages, EXCEPT for the Q6 base to emitter voltage.
You can see, all other transistors have a difference between 0.6 and 0,7 Volts between B and E.
Q6 has a difference of 2.3 Volts between B (-1.6) and E (+0.7) but I’m not deep enough in that thematic to find or explain the reason for that big difference.
It could be the tolerance of your DMM, we can only hope, that one of the experts comes up with an idea.

And as long as it works, I would leave it that way. The only old parts left in that area are C5 and C6 and it won’t harm, if you replace them as well, together with the recommended fly-back diode between pins 9 (anode +) and 10 (cathode -).
Click to expand...
Yeah. So I’ll research that diode connection. I saw that on your board.

I guess I should do the DC and bias procedures next. I know the service manual is incorrect and I have the corrected procedure. I’ll review and see which is done first when I get home. I’m so happy you stuck with me on this project. You deserve a medal.

I took a count of the number of parts I changed out and it came to 43. Most were transistors of course. I guess it was a combination of several things that caused the protection relay to not release.

I suppose sometime it may be a good idea for me to change some of the caps. But for now I’ll enjoy it.
 
More information about the fly-back diode and the SX-737
larryderouin

Post in thread 'Pioneer SX-737 biasing'

I saw Dewdude at the Mid Atlantic meet y'day. We talked about the main problem being the protection board and just sent him the latest BOM for the AWM-025 board, plus the skinny on the Flyback diode. He's gonna rebuild it with the parts on the BOM and add the flyback diode.

Larry
 
pa_200 said:
Congratulations, finally all pin voltages on the protection board look good and are close enough to the original values.

Same with the transistor voltages, EXCEPT for the Q6 base to emitter voltage.
You can see, all other transistors have a difference between 0.6 and 0,7 Volts between B and E.
Q6 has a difference of 2.3 Volts between B (-1.6) and E (+0.7) but I’m not deep enough in that thematic to find or explain the reason for that big difference.
It could be the tolerance of your DMM, we can only hope, that one of the experts comes up with an idea.

And as long as it works, I would leave it that way. The only old parts left in that area are C5 and C6 and it won’t harm, if you replace them as well, together with the recommended fly-back diode between pins 9 (anode +) and 10 (cathode -).
Click to expand...
Indeed the emitter of Q6 can never be .7 Volts, because it is connected to ground according the schematic. Probably measurement error.

Anyway, the (small) reverse voltage of Q5 makes it "not conducting" leading to Q6 also a small reverse b to e making it "not conducting", so this is normal, it enables the C6 cap to charge up and Q7 will switch on the relay, until a fault occurs (one of the three diodes drawing down voltage, OR Q6 base voltage rises due power loss quickly disengaging the relay (if your switch off the amp you want the realy disengage quickly).

So far, it looks this card works fine :thumbsup:
 
The diode was installed on pin 9 and pin 10.

I did the VR3-4 down to 0 volts.

I then did the VR1-2 up to 20mv (they were around 16).

Hooked up some speakers and heard stereo fm. Sounds good.

I’ll try the other inputs tomorrow.

So, maybe wait on changing out any more caps. I wonder if I should consider replacing the e-caps I used for the blue tantalums. Maybe another project.

I have to do a little work on the wood cabinet, but that can take it’s time also.
 
The best and most successful way if you start working with an old receiver is not to change only the actual bad part, depending on how deep you have to go and remove the boards.
If time and budget allow, you should first search the service manual for all known bad transistors and replace them with the recommended new parts.

Next there are all capacitors on the Power Supply, Protection Board and Power Amp.
Especially on the Power Amp, its recommended to replace always parts on both channels für an equal sound quality.
For more help and guidance, search for the newest BOM-List.
 
A few thoughts and explanations on the selection of capacitors from markthefixer.
For 2.0 µF and lower I prefer the non-polarized film caps.
markthefixer

Post in thread 'Pioneer SX-737 upgraded BOM list'

electrolytic capacitors are a compromise to fit that much capacitance in a reasonably sized package.
the compromise in this case is the chemistry and polarity business inside of it.

film caps have been getting better at stuffing more capacity into a space that can fit in our electronics.

film caps tend to last, frankly, forever.
electrolytic capacitors tend to dry out and fail.

that's it in a nutshell.

the UKL thing is a type of lower noise (electronic leakage) electrolytic capacitor. film caps are already low noise / electronic leakage.
  • Like
 
pa_200 said:
A few thoughts and explanations on the selection of capacitors from markthefixer.
For 2.0 µF and lower I prefer the non-polarized film caps.
markthefixer

Post in thread 'Pioneer SX-737 upgraded BOM list'

electrolytic capacitors are a compromise to fit that much capacitance in a reasonably sized package.
the compromise in this case is the chemistry and polarity business inside of it.

film caps have been getting better at stuffing more capacity into a space that can fit in our electronics.

film caps tend to last, frankly, forever.
electrolytic capacitors tend to dry out and fail.

that's it in a nutshell.

the UKL thing is a type of lower noise (electronic leakage) electrolytic capacitor. film caps are already low noise / electronic leakage.
  • Like
Click to expand...
Thanks. I’ll see if I can get those.
 
pa_200 said:
A few thoughts and explanations on the selection of capacitors from markthefixer.
For 2.0 µF and lower I prefer the non-polarized film caps.
markthefixer

Post in thread 'Pioneer SX-737 upgraded BOM list'

electrolytic capacitors are a compromise to fit that much capacitance in a reasonably sized package.
the compromise in this case is the chemistry and polarity business inside of it.

film caps have been getting better at stuffing more capacity into a space that can fit in our electronics.

film caps tend to last, frankly, forever.
electrolytic capacitors tend to dry out and fail.

that's it in a nutshell.

the UKL thing is a type of lower noise (electronic leakage) electrolytic capacitor. film caps are already low noise / electronic leakage.
  • Like
Click to expand...
So if I’m reading this correctly, my blue caps were 1.0uf, 2.2uf, and 4.7uf and therefore I would only need to use the film caps on the 1.0. And can use the e-caps for the other two.
 

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golfnut said:
So if I’m reading this correctly, my blue caps were 1.0uf, 2.2uf, and 4.7uf and therefore I would only need to use the film caps on the 1.0. And can use the e-caps for the other two.
Click to expand...
Hi still following along. Glad to see you are making good progress with @pa_200.

You don't need to use film caps at all, the choice is yours. Film caps do cost quite a bit more.

Film caps don't have a polarity and can drop right in place of polarized e-caps. Most people feel they are arguably better for audio use.

The choice is yours. One note, Low Leakage E-caps are getting hard to find and if you need to replace them film caps are a very good option.
 
mrk229 said:
Hi still following along. Glad to see you are making good progress with @pa_200.

You don't need to use film caps at all, the choice is yours. Film caps do cost quite a bit more.

Film caps don't have a polarity and can drop right in place of polarized e-caps. Most people feel they are arguably better for audio use.

The choice is yours. One note, Low Leakage E-caps are getting hard to find and if you need to replace them film caps are a very good option.
Click to expand...
Great and good to hear from you. Yes, @pa_200 stayed with me to the end. But, I had lots of help from you and others. I’ll keep what I have installed for now and it’s working but I’ll keep my eye out for the films.
 
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