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Pioneer SX-650 Protection Relay Issue

S

sx650pio

New Member
Hello everyone, I hope you can help me.

A few days ago my beloved SX-650 suddenly stopped working during a listening session. I turned it off and on again and noticed that the clicking noise from the protection relay was missing, so I went to this forum and looked for answers. I got my voltmeter and measured everything and from what i can see the values seem okay in my opinion. Some slight variations but not much. During the measuring the protection relay suddenly clicked but after a few seconds it went off again. This happened a few times.

So I imagine that it has something to do with a loose component. What is the best way to find the little troublemaker? I even looked closely on all the contacts but could find anything.

I would like to prevent resoldering everything because I'm sure that I will cause more harm than good in the end.

If it helps here are my measurements:

AWR-117:
1: 40.53 ac
2: 40.53 ac
3: 0
4: 28.09 ac
5: 37.28
6: -37.25
7: 27.95 ac
8: 0.374 ac
9: 8.5 ac
10: 8.35 ac
11: 0.38 ac
12: 0
13: -53.7
14: 51.9

GWR-101:
A: 0.036
B: 0.012
C: -0.012
E: 0.05
F: 0.026
G: 0.004
H: -35.75
P: 34.16
30: 31.24
31: 8.37 ac
32: 1.121ac
33: 0
34: 0
35: 13.95

GWH-101:
1: 36.7
2: 0.036
3: -36.7
4: -0.11
5: 36.8
6: 0.05
7: -36.5
8: 0.04
9: 0
10: 0
11: -19.3
12: -35.75
13: 0
14: 34
15: 0
16: 0
17: 0.02
18: 34
19: 0.013
20: 34.03
21: 0.003
22: 0.001
23: -53.5
24: 0
25: 0
26: 51.4
27: 22.44
28: -35.8
29: 34.02

SP-40W Left:
1: 36.9
2: 1.212
3: 0.05
4: 0.026
5: -36.95
6: -1.2
7: 0.004
8: 0

SP-40W right:
1: 36.9
2: 1.177
3: 0.036
4: 0.012
5: -36.9
6: -1.175
7: -0.01
8: 0
 
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Since it clicked on when you were probing, it very well could be as you stated - a bad solder joint.

Is it just me, or do others also think the power amp board on the 650 is a pain to get to. At least you don't have to worry about setting the bias or offset.

Good luck!
 
open up d7 for a while see if it stops.
subtractive troubleshooting.

if it were d8 or d9 dc voltage you would have heard a pop.

if d7 stops it, look at Q5 & Q6 over current detectors. (ksc1845)

if you have the original SANYO sky blue troublemaker caps at C21, C22 that's probably it.
 
I also have a 650 with the relay constantly clicking on/off. I thought I had fixed it. The differential transistors (q1,q2)on the power amp board are almost always an issue. So I swapped them out as well as q3,q4 and c13,c14. After doing so, it worked well. I sold the unit and after about 2 weeks of use, the buyer called and said it was doing the same thing. So I'm thinking maybe one of those new transistors (yes, from China) is bad.
I should add, I have had 3 other 650's and one of the other ones also had a bad 2S798 differential transistor.
 
I have not resolved mine yet. Haven't gotten around to looking at it. I also had a 650 where on the GWR-101 board, Q8 went, and R51 (33ohm) connected to the collector went as well. In that case, the relay never clicked on, and the meters didn't have any power. One in the same. In another, I noticed fluctuating voltage on q4 collector which was driven by the infamous 2s798. Once that was replaced, it fixed the issue. Now, as I said back in my post on March 8. I did the same in this latest 650, and it worked for a while. Which leads me to believe the 798 I replaced it with is still an issue. But I haven't looked at that in some time.
 
Quattroguy. Replace the 798 with a pair of KSA992's. lightly coat the flat sides with heatsink grease and heatshrink them together with the flat sides touching after installing them in holes and before soldering all 3 legs each. Go ahead and solder the furthest leg and bend/twist as needed to make them flush against each other without crossing or touching the legs together. If needed heatshrink tubing or spaghetti tubing on the legs. With the ksa992's in the mounting holes correctly they will or should be facing each other. The heatsink grease an heatshrink is to thermally stabilize them together. You will need to match them, so order a dozen or so.
 
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