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

[golfnut]

My apologies, I totally missed that. Early morning looking at capacitance and bypassed ESR completely.

That cap needs to be swapped out. I wish he had an axial version instead of the radial. It could be used to test and replaced later for an axial. That should greatly improve the power supply.

Not a problem. So I think I would have to put the positive leg in the d6 or d7 positive area. Does that make sense?

 

[fucanay]

Not a problem. So I think I would have to put the positive leg in the d6 or d7 positive area. Does that make sense?

The board is marked with a +. So positive to that side. Don’t get that wrong. That would be quite a sound.

 

[golfnut]

The board is marked with a +. So positive to that side. Don’t get that wrong. That would be quite a sound.
View attachment 3698344

Agree. Sorry but I wasn’t clear in my question. The leads on the new cap cannot reach the axial points. It seems like, but I can’t find it now, that someone had the same problem and put the positive lead of the new cap in a different hole. D6 and D7 are on the same positive trace as the old cap so I was asking if it was appropriate to use one of those for the positive lead of the new cap. It was good to hear this cap may be one of the problems.

 

[pa_200]

This solution/poistion should work

 

[fucanay]

Agree. Sorry but I wasn’t clear in my question. The leads on the new cap cannot reach the axial points. It seems like, but I can’t find it now, that someone had the same problem and put the positive lead of the new cap in a different hole. D6 and D7 are on the same positive trace as the old cap so I was asking if it was appropriate to use one of those for the positive lead of the new cap. It was good to hear this cap may be one of the problems.

There aren't any unoccupied holes on this board and none of the occupied holes have room for two leads.

This solution/poistion should work

View attachment 3698458

This is probably the best solution in a pinch. Do note that there is heat shrink on one of the leads. I'd probably cover both just to be safe. Pioneer ever covered the jumper that's on the board.

If it's me, I'm ordering an axial cap for that spot, which is what I did.

 

[golfnut]

There aren't any unoccupied holes on this board and none of the occupied holes have room for two leads.



This is probably the best solution in a pinch. Do note that there is heat shrink on one of the leads. I'd probably cover both just to be safe. Pioneer ever covered the jumper that's on the board.

If it's me, I'm ordering an axial cap for that spot, which is what I did.

View attachment 3698470

I found a repair shop about 30 mins away and he had one to sell. He said bring mine and we’ll test it. He had a much fancier tester. The good news and bad is that my original tested at 1 ohm and just under 1000uf. So apparently my ESR tester isn’t that accurate for capacitor ohms. I will reinstall the old one. I’m not sure where we stand but maybe I should update the ps pin readouts.

 

[pa_200]

If you go with a fully charged cap to the little tester, it can damage the device. I experienced that with my first one. And since we have a high static charge here, it's pure luck if it even displays anything at all.

 

[gslikker]

Repeating myself, I suggested Q1 to be defective in posting 166, so do not forget measuring the voltages with respect to zero on both transistors and adjacent resistors.

 

[golfnut]

Repeating myself, I suggested Q1 to be defective in posting 166, so do not forget measuring the voltages with respect to zero on both transistors and adjacent resistors.

I’ll pull Q1 on 057 and do the 6 point diode test. I’m not sure what you mean on the resistors unless having the unit on, black to chassis and red to the each of the legs on the close resistors. If that’s the case, I’ll report back on those readings. I’ll also get the reading on Q2 if that is correct also. Thanks

 

[fucanay]

I’ll pull Q1 on 057 and do the 6 point diode test. I’m not sure what you mean on the resistors unless having the unit on, black to chassis and red to the each of the legs on the close resistors. If that’s the case, I’ll report back on those readings. I’ll also get the reading on Q2 if that is correct also. Thanks

Do you have new transistors for the power supply? If so, it's probably best that you just change them regardless of what the 6 point test says. Especially Q1 that has been living it's life without a heat sink for 50+ years.

 

[golfnut]

Do you have new transistors for the power supply? If so, it's probably best that you just change them regardless of what the 6 point test says. Especially Q1 that has been living it's life without a heat sink for 50+ years.

I have already changed those previously on the ps board. But, the Q1 could now be bad. I’ll check it out tomorrow. Thanks

 

[fucanay]

I have already changed those previously on the ps board. But, the Q1 could now be bad. I’ll check it out tomorrow. Thanks

Those were not mentioned in this post.

G

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

Feb 2, 2026

I don't think you need to begin a new thread and I don't know that you need to be led. You certainly shouldn't quit. This unit is in your hands and you are in control of the project. But building a comprehensive "reset" post would be useful. Having it all in one place rather than having to go from page to page would be good. Reading as many other posts with regards to these types of projects is helpful as well. As is patience and perseverance.

Give us:

• The original fault and the current state of the behavior

The original fault in the unit, and still the same, was that...

• golfnut

 

[golfnut]

Those were not mentioned in this post.

G

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

Feb 2, 2026

I don't think you need to begin a new thread and I don't know that you need to be led. You certainly shouldn't quit. This unit is in your hands and you are in control of the project. But building a comprehensive "reset" post would be useful. Having it all in one place rather than having to go from page to page would be good. Reading as many other posts with regards to these types of projects is helpful as well. As is patience and perseverance.

Give us:

• The original fault and the current state of the behavior

The original fault in the unit, and still the same, was that...

• golfnut

Sorry they were, I just went down and double checked.

 

[gslikker]

I’ll pull Q1 on 057 and do the 6 point diode test. I’m not sure what you mean on the resistors unless having the unit on, black to chassis and red to the each of the legs on the close resistors. If that’s the case, I’ll report back on those readings. I’ll also get the reading on Q2 if that is correct also. Thanks

Of course, I just mean measuring voltages having the unit on. Having C B and E voltages of both transistors, you already have most of it, only remaining is the intersection of R4 and R5, the 1.5k ones, expecting voltage just halfway between collector and base voltage of Q1.

Easiest is just jot down in the schematic having the voltages as they should be on page 57 of the manual.

If you want to pull them out anyway to check, probably your Chinese testing device will give you the HFE and VBE figures as well.

 

[golfnut]

Of course, I just mean measuring voltages having the unit on. Having C B and E voltages of both transistors, you already have most of it, only remaining is the intersection of R4 and R5, the 1.5k ones, expecting voltage just halfway between collector and base voltage of Q1.

Easiest is just jot down in the schematic having the voltages as they should be on page 57 of the manual.

If you want to pull them out anyway to check, probably your Chinese testing device will give you the HFE and VBE figures as well.

The unit kept going in and out of protection mode during these measurements.

The base on Q1 and the collector on Q2 jump around that I could not really get a good reading.
Q1 C was 48vdc
Q1 E was 33.0 to 33.5
Q1 B was 19 to 30

Q2 E was 13.9
Q2 B was 13.3
Q2 C was 16 to 30

R4 & R5 was 41.2 vdc
R5 was 34.9
R4 was 48.1

See picture attached

 

[fucanay]

Did you reflow all your solder joints on the Power Supply. There are quite a few that look terrible on the pictures.

This feels like a bad ground reference. Did you do what pa_200 suggested above? I'd add that not only you joints are an issue, but also the originals. The picture below, which is one side of R3 and goes directly to the collector of Q1, shows what looks like a crack all the way around.

At this point on the power supply, you're going to have to methodically go from joint to joint with some flux and re-flow everything. If it doesn't re-flow well, remove solder and re-solder. We simply have to have stable, non-drifting voltages to be able to move on.

 

[golfnut]

This feels like a bad ground reference. Did you do what pa_200 suggested above? I'd add that not only you joints are an issue, but also the originals. The picture below, which is one side of R3 and goes directly to the collector of Q1, shows what looks like a crack all the way around.

At this point on the power supply, you're going to have to methodically go from joint to joint with some flux and re-flow everything. If it doesn't re-flow well, remove solder and re-solder. We simply have to have stable, non-drifting voltages to be able to move on.

View attachment 3699480

Ok will do. Thanks

 

[golfnut]

This feels like a bad ground reference. Did you do what pa_200 suggested above? I'd add that not only you joints are an issue, but also the originals. The picture below, which is one side of R3 and goes directly to the collector of Q1, shows what looks like a crack all the way around.

At this point on the power supply, you're going to have to methodically go from joint to joint with some flux and re-flow everything. If it doesn't re-flow well, remove solder and re-solder. We simply have to have stable, non-drifting voltages to be able to move on.

View attachment 3699480

Here is the latest on the ps board with reflow soldering. Unit was unplugged but I did experience a spark when I touched C3 and C4. You can probably see that on the board.

After the reflow, I turned the unit on dbt and bright light to dim. So, I then went full power.

There was no change in the unit. It took about 30 sec for the relay to click off then on again.

So when I have the unit on, I can hear a faint noise. Not a rhythm and not constant. But like soft grinding that stops and starts.

Pictures below are of the most recent solder reflow.

 

[fucanay]

Here is the latest on the ps board with reflow soldering. Unit was unplugged but I did experience a spark when I touched C3 and C4. You can probably see that on the board.

After the reflow, I turned the unit on dbt and bright light to dim. So, I then went full power.

There was no change in the unit. It took about 30 sec for the relay to click off then on again.

So when I have the unit on, I can hear a faint noise. Not a rhythm and not constant. But like soft grinding that stops and starts.

Pictures below are of the most recent solder reflow.

The relay click is not what we're even looking for right now, that will come later. We're looking for correct voltages on the power supply. If those aren't right, we can't even address anything else.

Why would there be a spark on C3/C4 that would create a mark like that? Anybody?

 

[pa_200]

The relay click is not what we're even looking for right now, that will come later. We're looking for correct voltages on the power supply. If those aren't right, we can't even address anything else.

Why would there be a spark on C3/C4 that would create a mark like that? Anybody?

If you look at the big schematic one page 27, C3 and C4 are connected via pin 9 and 10 to the big filter caps. And as long as they are not discharged, bangs, sparks all you don't want.