Pioneer SX-828 Troubleshooting help - Protection Relay not firing

[tclarkbar]

Hello! I'm hoping I could get some troubleshooting advice for an issue with my Pioneer SX-828. This receiver fell into my lap recently and was kind of working before I decided it needed a refresh. I'd like to say that this forum has been a wealth of information while I've been working on it the past few weeks. I'm pretty sure I'm the 2nd owner of this receiver, but I do think it's been opened up in the past for repair. I have some old receipts from the late 70s that confirm this, I just don't know the scope of the work.

Originally the receiver would turn on but none of the lights worked. I tested the AUX input, FM radio, and tape inputs, those all worked. One channel worked well on all the outputs and the other was really really quite. I believe the left channel sound fine (A, B, & C) and the right channel was the quite one. But I didn't write it down and am not 100% sure on that.

I've made it though most of refresh and now the protection relay isn't firing. I purchase parts from peace.love.and.music (ebay) for the refresh. The complete rebuild kit, the LED light kit, and the OnSemi MJ21195G & MJ21196G Transistors.

As it sits now, I've changed out the fuse lights and reworked the following boards: power supply unit AWR-010 , protection board W28-008, head amp unit W21-002, AF unit AWK-012, and the main amp unit AWH-010. I've also replaced the 3 big stand alone caps. All the lights kicked on once I cleaned all the pots and refreshed the AF unit AWK-012.

I've been testing it as I complete each board using a dim-bulb tester, but TBH I didn't pay enough attention to the relay to know what board refresh made it stop working.

Anyway, at this time I'm not sure if I actually have a low voltage problem or an issue with the protection board. I've not changed the relay yet, but I can ground pin 9 on the protection board and it clicks.

Here are my voltage readings as it sits now. (note: vr1-4 on the main amp are adjusted to their mid point for now).
Pins 9, 10, 19, 20, 21, & 23 on the amp board seem a little off from my research of what they should be.
Same with 9, 14 , 15, & 17 on the power supply board.

Protection Board W28-008

Pin
1	-34mV
2	-12.96V
3	-29mV
4	gnd
5	-67mV
6	7mV
7	-11mV
8	-45mV
9	34.94V
10	34.96V
11	34.97V
12	0.432VAC (note this is a W28-008)
TP1	31.68V
TP2	35V

Power Supply Board AWR-010

1	GND
2	12.71 V
3
4	4.34 V
5	31.3 V
6	33.8 V
7	35.06 V
8	35.87 VAC
9	43.5 V
10	35.90 VAC
11	GND
12	29.58 VAC
13	29.58 VAC
14	37.65 V
15	37.64 V
16	GND
17	-38.13 V
18	35.28 VAC
19	-27 mV
20	-27 mV
21	-28 mV
22	-28 mV

power amp AWH-010

1	1mV
2	1mV
3	GND
4	GND
5	GND
6	GND
7	-28 mV
8	-26mV
9	37.64 V
10	37.76 V
11	-11 Mv
12	12 mV
13	0.571 V
14	0.609 V
15	-0.587 V
16	-0.621 V
17	-42 mV
18	-60 mV
19	-37.84 V
20	-37.69 V
21	37.87 V
22	-13.06 V
23	-38.28 V
24	GND
25	1.136 V
26	1.173 V
27	-0.915 V
28	-0.873 V

Any help is greatly appreciated.

 

[eiraved]

Welcome to AK!!
It's a breath of fresh air to have a new member lay out their troubleshooting steps, down to the voltage measurements, thank you! Makes it so much easier to help.
I'm not an expert on this Pioneer but someone should be along shortly to assist.