Attempted SX-1250 repair with pics

My first post in the Pioneer section. A few months ago I came across an sx-1250 in great condition and was lucky enough to get it. Man, what a magnificent beast! The only glitch is that one channel fades out and in occasionally. markthefixer gave me a helpful nudge to post what I'm doing in order to get some help.

I took pictures hoping to help others (and so I can get things back together :yes. One pic shows which front panel screws are for the switches and pots boards. Others show the boards themselves.

The follow up reply has a pic of the button boards and a top down view showing the honkin' big caps. Another pic shows the slots at the bottom of a switch where DeOxit can be sprayed as described in another post. Before finding that post I had carefully pried off the cover of one switch only to find it wasn't worth the effort because it didn't give any better access to the contacts.

There are also two pics showing how to remove the cover of a button. But for the inexperienced (like me) I think spraying DeOxit into the slits along the edges of the cover is a better idea. I kind of munged up the muting and multipath buttons when I put their covers back on. They are a bit off mechanically now. One doesn’t stay in sometimes and the other pushes hard. I may have jammed their springs or something. Any ideas for a fix?

OK, so far I've done the DeOxit thing on the switches, buttons, and balance pot. I haven't done the sealed volume pot. I also haven't done the input selection buttons because that board wasn't going to come out easily. Instead, leaving that board in place I sprayed those buttons as far down the shaft as I could get, as described in another post. I will drill and spray the volume pot if that is warranted.

But I did some basic troubleshooting and got some interesting results that make me think it's probably not the volume pot. With the power on I found these repeatable ways to bring the faded channel back (until it fades out again):
1) Flip the Loudness switch on
2) Rap the top of the left rear honkin' big cap with my knuckle
3) Increase the volume (jiggling the shaft of the volume control did nothing)
4) Turn on a fluorescent light plugged in to the same outlet as the 1250!!

So, do I have to bite the bullet and replace the big caps - I don't see any signs of leaking. Or are there other things worth trying first? And where the heck would I get replacements for the big caps anyway?

More pics.

Doubt your main caps are bad, sounds more like dirty contacts on the protection relay. Needs to be disassembled and the contacts cleaned.

The relay is on the protection board, and can be replaced IF you can
1. desolder without board damage, the old one
2. widen the holes to fit the new relay
3. solder in the new relay.

To widen the holes you need an 0.030 or 0.040 size drill bit AND appropriate drill

mouser.com:
653-MY4-DC24 ~$5


I have done this on 1250's - you need a STEADY hand, or you can trim off half the lug through the hole in the center - a bit kludged, and be sure the extra height doesn't hurt you.

Of course you can try cleaning the relay first.

p.s on the switches, the push switches are squirted from the front through the spring, anything else that is effective, is master or wizard level work with a LOT of risk.

re: switches not behaving, mechanical reassembly was not correct, probably into the panel as opposed to the buttons themselves, didn't you check the switch action after putting on the covers, IF you did then it was the reinstallation into the panel. - pictures won't help.

Buttons: I bet the springs popped out, and you didn't get them seated properly in their plastic 'housing' before you put the cover back on. A section of the spring is probably hanging outside the housing.

Mark...why do the holes need to be enlarged for the relay? The MY4 relays are the same as what comes out...Mouser has 17 in stock.

653-MY4-02DC24
http://www.mouser.com/ProductDetail/Omron/MY4-02-DC24/?qs=eORE%2bZ%2b0Crv7hRNHqogGYw==

I ended up getting the 653-MY4-DC24 without the 02 in the number.

Sorry Master, I was unaware....

The only place I didn't look at was the pdf online catalog page (where they put that darn asterisk that means pcb terminals), the .pdf spec file and product web pages for the two are indistinguishable.

I'm going to get some 653-MY4-02DC24 's to check them out. And a few others as well - sort of multiple choice to see what works best. I HATE revving up the PCB drill.

The non-02 653-MY4-DC24 has a pierced tab terminal, and a square case without ears. I was successful in a sa-9500 in fitting the new core into the old case that has the bottom ears, after a minute with some die files, removing a little ridge on the core and the ends of the arc suppressor, then dumping the orange indicator lever, thus no standoffs needed.

A long time ago I used to work at Magnecraft (relays) when they still had some manufacturing left in Chicago, making final test and qc fixtures and equipment... I know a bit about relays...

I really appreciate all the input. When I tried tapping the relay when the channel had faded just now, the channel came back.

In order to avoid another bonehead move like my one with the push switch covers, let me ask before doing: Is it best to remove the protection board in order to clean the relay contacts, or just do it with the board in place? Can I do the cleaning by just removing the clear plastic cover and spraying DeOx? Does the cover come off by depressing the little black tab inside the recess on both sides at the base?

If I end up removing the protection board, does it simply unplug and come straight up and out after removing the two screws at its base?

Feels good to be moving forward.

dd123 said:

If I end up removing the protection board, does it simply unplug and come straight up and out after removing the two screws at its base?

Click to expand...

Unplug the wire harness from the bottom of the board. You'll need to remove the receiver's bottom cover. Then remove the 2 mounting screws for the board from the top. Now you have the board out to work on out of the receiver. Might as well recap it it as well. The stabilizer board and driver boards are the same way also. Just becareful with the driver boards as they have a temp protect diode which are connected to the heatsinks and the diode leads are fragile. I would recommend that those should be recapped also if not done before. Hopefully you've found the recap list for the 1250 here on AK and have downloaded the SM. Lot's of info here on AK that has been previously posted that should answer most of your questions. If not feel free to ask. Congrats on your new 1250 aquisition.

dd123 said:

I really appreciate all the input. When I tried tapping the relay when the channel had faded just now, the channel came back.

In order to avoid another bonehead move like my one with the push switch covers, let me ask before doing: Is it best to remove the protection board in order to clean the relay contacts, or just do it with the board in place? Can I do the cleaning by just removing the clear plastic cover and spraying DeOx? Does the cover come off by depressing the little black tab inside the recess on both sides at the base?

If I end up removing the protection board, does it simply unplug and come straight up and out after removing the two screws at its base?

Feels good to be moving forward.

Click to expand...

Yes, remove the board, it has connectors. Clean and deoxit the connector pins while out.

deoxit will not suffice for the relay, burnish the contacts with ultra fine abrasives (800-1200 grit) - most of the gold flashing will be gone already - so you're just removing burned material. (thus the EchoWars part number for a new relay that doesn't require drilling).

That picture a few posts back shows the shim method of removal. IF you're adventurous, shims made from an aluminum pop can are stiffer - but SHARPER.

markthefixer said:

Clean and deoxit the connector pins while out.

Click to expand...

Damn I forgot to add that. A Scotch Brite pad cut to size to clean around the board's pins works great after deoxit. Don't forget to apply some deoxit to the wire harness pin connectors.

I used Echowar's suggestion while back on using Brasso on the pins. It really removes all those oxides without scratching much metal off. Be sure to clean brasso off the pins when done.

Good call you guys. It's too early to be sure, but I want to give an early report that cleaning the relay contacts (and the board connectors) may have fixed the problem. As suggested, Brasso on the board pins, DeOxit in the female ends, and very fine emory paper on the relay contacts worked great. Before the cleaning, tapping lightly on the relay would cause one channel or the other to fade or come back. Now tapping does nothing and there hasn't been any channel fading.

I always thought a relay was either fully open or fully closed, so with a channel fading but not cutting out fully, I wasn't thinking relay at all. Glad to learn from those who have gone before.

After enjoying the lack of fading for a day or so I'll go back and check the springs on the two push switches I munged up. I'm on a roll thanks to all the input!

I also want to check out any adjustments I can do with a DMM. And I'm trying to talk myself into recapping...

dd123 said:

Good call you guys. It's too early to be sure, but I want to give an early report that cleaning the relay contacts (and the board connectors) may have fixed the problem. As suggested, Brasso on the board pins, DeOxit in the female ends, and very fine emory paper on the relay contacts worked great. Before the cleaning, tapping lightly on the relay would cause one channel or the other to fade or come back. Now tapping does nothing and there hasn't been any channel fading.

I always thought a relay was either fully open or fully closed, so with a channel fading but not cutting out fully, I wasn't thinking relay at all. Glad to learn from those who have gone before.

After enjoying the lack of fading for a day or so I'll go back and check the springs on the two push switches I munged up. I'm on a roll thanks to all the input!

I also want to check out any adjustments I can do with a DMM. And I'm trying to talk myself into recapping...

Click to expand...

Check out Carveit's thread on Pioneer caps designation http://www.audiokarma.org/forums/showpost.php?p=3012505&postcount=11

Then compare to the Nichicon pdf file I've attached when you order your caps. Takes a lot of the guess work out. After a couple times you'll get the hang of it.

Fixed the push switches

Hey, I actually fixed the two push switches I munged up. I could see the problem after lots of close-up inspection with a magnifying glass and good light. (OK, so my eyes aren't what they used to be...)

There is a vertical spring underneath the white cap of the push switch. The bottom of that spring needs to be on top of the brown switch cover. The only way for that to happen is to lift the bottom of the spring and slip the cover underneath it. I lifted it from the back with a pin. In order to have enough room for the cover to get under the pin, I pried up the back metal tab on both sides of the switch so that the back edge of the white cap could raise up up a bit. I bent them back down when the cover was on and secured. See pics, even though they're not the greatest.

There may well be a better way of doing it, but this is what I came up with. I never use the two switches but the beast deserves to be 100% right. One switch turns off FM Muting, which I never want to do. The other is the Multipath switch, which I never figured out what the heck it's good for.

THE MOST IMPORTANT THING IN MY OPINION IS TO NEVER REMOVE THE BLEEPIN' COVERS IN THE FIRST PLACE!!!! :nono:

And thanks for the great cap info!

Multipath switch:

There is a signal that feeds the signal strength meter. The signal to the meter is averaged out by a capacitor so the needle is steady.

The multipath switch sends that raw signal to the amplifiers, so you can HEAR the multipath.