Pioneer SX850 relay switching off problem

I just read through Nicks amazing adventure with a similar problem with his sx850 and I am hoping I do not have to do as much of a rebuild as he did but all the advice and encouragement that he got was excellent. All the back and forth is very informative to me, another SX850 owner with that damn relay problem. I hope I don't have to go through what Nick went through and my voltages are odd in a different way. I am the original owner and I Love this receiver. I am ordering some Walsh Ohm 2s and really want to run them with my sx850 but I have a sometimes intermittent relay problem but right now the relay won't actuate at all. I have downloaded the bad schematic for the 850 and the good maintenance manual for the 750, wish I could find that for the 850. I did have one guy work on this unit and he wrote on the receipt that "intermittent power caused by bad solder connection INSIDE the power transformer- normally this is a fatal problem, got lucky was able to gain access to internal transformer wiring and resolder connection." Well that's cool and I appreciate him describing what he did but it didn't work for very long, and went back to it's old relay behaviors. I put it away for a few years and pulled it out this week turned it on and it worked pretty amazingly well for a week and now it is back to it's old habits. Right now the relay won't click on at all. I did the tests on the ??power supply board that you mentioned and to me the voltages look very different than what Nick was running into. I got
1 0v
2 .805v
3 .805v
4 3.74v
5 3.75v
6 17.98v
7 17.97v
8 12.14v
9 12.13v
10 12.14v
11 8.95v
12 0v woo hoo!
13 13.1v
14 50.0v
15 18.55v
17 44.3v
18 44.4v

To tell you the truth I am not sure if the relay had actuated or not when I took those readings. It worked ok for the last week, it started acting up this morning and as I have opened it up and looked around and not done much to it really, it went from intermittent to won't actuate at all now. I would Love to hear the Walsh Ohm 2s that I have ordered through the sx850 any help or suggestions would be greatly appreciated. I have had this receiver since 1978 and after listening to it again, well last night, I really want to get this problem fixed. Nial in Santa Fe

I have checked for any loose solderings on the diodes that he replaced and I have not done the adjustments that he did and I don't have a bulb tester but that thing is so cool! I am thinking about looking at where he soldered the transformer but I am really wondering if it is the diodes or adjustments, or the relay itself, I used to think bad relay but the more I research the less I think that. It used to click, it don't click no mo, it's broke! I have blamed relays so many times when they were not the problem, i'm getting over that mistake. Anyway, if anyone can make more sense out of those voltages than me I would really appreciate it. Sorry for the long post but I think I am to page 2 or 3 of Nicks Awesome adventure! Thanks in advance. Nial

Now the orange lights for the speakers and input selection are not lighting up. It's getting worse.

Here's a good schematic:

Pioneer sx-850

Check fuses 2 and 3, both 1 amp specs.
Take AC volt readings from both sides of all the fuses.

Or half the Power supply is dead. :scratch2:
In that case you and Ultimatt will have something in common.
Rebuilding the PS.

Let me tell you, that was certainly an adventure ! but starting out at the seam of my pants, after all the excellent help here along the way, things
began to make sense to me and started to dial in ( mentally ) at the
overall scope. you too will experience this and one day soon you can look back at this while enjoying that wonderful 850 and say WOWO!!! these guys
here are amazing and so generous with all the help. *My 850 by the way
is performing amazingly and sounds ( strangely ) better than my 950 in
Sonics and power. good luck

Nick

Quick reply I pulled the fuses and checked for continuity and they were ok, but I will go check the voltages. Thanks for the schematic. I was a Xerox Tech for 13 years but I will still call myself a dummy when it comes to receivers.

Also when the relay intermittantly clicks, it works perfectly in both channels. Wouldn't a burned out half of the power supply not do that?

Study the schematic. The voltages you posted for pins 9 and 10 power the protection board. You posted only half the required voltage needed to operate the protect circuit.

Yantraimages said:

Quick reply I pulled the fuses and checked for continuity and they were ok, but I will go check the voltages. Thanks for the schematic. I was a Xerox Tech for 13 years but I will still call myself a dummy when it comes to receivers.

Click to expand...

Circuits are circuits, and voltage is voltage. Just report back with the results of the PS readings and someone here should be able to point more closely to the likely cause(s).

9 and 10 Thank You, I am still having problems with getting set up on understanding the schematics and being able to see them while I'm working easily. I have a nice setup but need to get them on my other computer with the big screen, 42inch monitor. Then I can see what I'm doing better. Therefore I am not sure which is F2 and F3 but I have the unit sitting up on it's back looking at the 5 fuses the board is labeled from top to bottom 24-28 top to bottom. so this is what I have from top to bottom
24 -4 to -5mv left -2 to -3mv right
25 -5 to -6mv both sides
26 -9mv both sides
27 -61mv left .196v right
28 -.63mv left -.71mv right

those readings fluctuate a lot in the mv range I don't think the fuses are generating much energy.But do you think it is worth replacing the fuse on the #24 which seems like the fuse has a little resistance? probably no big deal huh? I mean we are talking fluctuating millivolts.

You know I just noticed something, for years with Xerox I went through RAPs (repair procedures) traced voltages and found which board was bad, but after awhile I could narrow it down much easier with my nose. On the board with the fuses over on the right by the heat sinks there are some little black transistors which smell fishy. Hmmm.

The nose knows

The fuse voltages are AC and should read in the 10's of volts. Black probe to chassis and red to fuse holders. When checking the holder; probe the wire side first, making sure you have voltage. Then check the other end holder to make sure the voltage is reaching the board side through the fuse. Quick and easy.

The AC then is rectified to DC through the diode bridge; so you can check to make sure good DC power is available to the PS regulators.

Good practice.

Actually the back of that board looks pretty good. The front is discolored and very minorly blackened. If those heat sinks put out a lot of heat that could be it.

I was reading dc, sorry, let me do it again. i got the black and red right. Uno Momento, and mucho Gracias !!!

Much more straight forward in ac mode, the first one is the only one showing any resistance all the others were the same through the fuse.

24 left 7.5v right 6.8v
25 46.8v
26 46.8v
27 20v
28 20v

/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Previews/2015/01/04/20150104-180338/YA8qvJfmTeO3NgkOZi68nQ/IMG_0356.jpg
/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Previews/2015/01/04/20150104-180338/dMGpPxoJQHmfJVZc1xW04w/IMG_0357.jpg
/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Previews/2015/01/04/20150104-180338/btRZAA8wTgWWYoTtSswYCg/IMG_0358.jpg
/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Previews/2015/01/04/20150104-180338/5JpJOmmKQROLWYQ5Ix9XkQ/IMG_0359.jpg
/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Masters/2015/01/04/20150104-180338/IMG_0360.JPG
/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Masters/2015/01/04/20150104-180338/IMG_0361.JPG
/Users/nialconnolly/Pictures/iPhoto Library.photolibrary/Previews/2015/01/04/20150104-180338/neu7c8hRSrKW7hUgEslEQg/IMG_0362.jpg

Yantraimages said:

Much more straight forward in ac mode, the first one is the only one showing any resistance all the others were the same through the fuse.

24 left 7.5v right 6.8v
25 46.8v
26 46.8v
27 20v
28 20v

Click to expand...

There seems to be a bit of excessive voltage drop at the first fuse (FU6) which may be due to a weak fuse clip or solder connection, weak fuse, or possibly the installation of an incorrect type (MDL) fuse.

The incoming voltage seems to be correct at Pins 25/26 (a wee bit low, but acceptable), and the voltages at Pins 27/28 should be acceptable.

Check the DC voltages at Pins 2, 4, 6, 8, 11, 13, 14, and 15 on the PS board if you can.

EDIT: It may also be useful to check the DC voltages on the Protection board (AWM-062) at Pins 1, 2, 3, 5, 6, 7, 8, and 10. Also check the AC voltage on Pin 12.

Well I guess I screwed up posting pictures.

Thanks for the suggestion I will. Nial