SX-650 help

capo72 · Jan 3, 2007

I aquired a sx-650 a few months ago and I really like it. It has one problem and i've decided to dive in and see if I can fix it. I like vintage stuff (also have a tx and sa-7800), and I can solder and read schematics. I'm just not a good trouble shooter yet, but i'm trying to learn so any help is appreciated.
When I turn on the 650, I get a sizzling/crackling sound that I think is coming from the power supply area. Along with this noise the lights flicker (which also makes me think power supply) This lasts for about 7-10 seconds, which is followed by a click (relay?) then the lights come on and everything is fine. Everything seems to work great except for this hard time turning on. Any help with this problem is greatly appreciated. Thanx for your time,

Jeremy

TiberiuS · Jan 3, 2007

Sounds to me like it could be a loose transformer winding, had the same thing on a Sharp music center (remember those???) for years now, never done any harm; exactly the same symptoms as you describe...sizzling sound from the transformer, flickering lamps etc, then fine.

Looking for burned components is always a good start and check the underside of the board for bad solder joints.

Good luck

Regards, TiberiuS.

markallen · Jan 3, 2007

I'd bet this is related to the power switch.

I bought a mint-condition SX-650 off eBay one time, seller said it wouldn't fully power up so I got it CHEAP. Acted like you are describing, except apparently was a step worse than where yours is currently as it wouldn't eventually clear up. I ended up taking it apart and it was the power switch. IIRC, there was a little bolt through the switch body that was missing the nut, allowing less than ideal contact (forgive me, it's been awhile, dredging up recollections here). Once I cleaned the switch and replaced the nut (THAT was a treat, tight fit, had to find a nut with the right threads and modify it to fit, or SOMETHING like that!), it worked/works perfectly. A beautiful receiver.

IMO, the lower end of this series (through the SX-750) does not have the greatest power switch design, incorporated into the speaker selector. You had to graduate to the SX-850 to get an actual separate power switch.

Strawman · Jan 3, 2007

More than likely the power switch, they were problematic from the 450 on up. The 850 does have it's own toggle switch. I would try a search using 650 power switch, pretty well documented. It may or may not be able to be cleaned/burnished to operating condition. If so, I would advise keeping the switch set properly and using a power strip, or preferably, a Pioneer timer to handle the on/off switching load to avoid future arcing of the contacts, which is what's causing the noise. It may be the transformer as Tiberius found, worth checking. I think Mark Anderson had a 650 he was parting out if you can't repair yours. I can also upload the service manual if anyone would like a copy. I keep forgetting the member that uploaded onto his site, I think he's in france?

markthefixer · Jan 3, 2007

Power switch arcing, the sx-450, sx-550, sx-650 and sx-750 all have the same switch and the same problem.

This thread discusses the problem WITH PICTURES.. Read the ENTIRE THREAD , and follow all the links through too, by the time you finish you will be well armed with HARD EARNED information.

It's not fun, but it can be done.

The switches have two variations, (possibly three) one variation has a RIVETED switch body that must be opened to access the contacts. We've only seen one of those. To close it up you will need #2 or #3 size screws from a hobby shop. 4-40's are a bit too big. The rest generally have plastic cases held together by the switch hardware, with the possibility of the case being ultrasonically welded shut (but we haven't had reports of one of THOSE yet).

Strawman · Jan 3, 2007

That's what you need, Mark is much more organized than me. He's walked plenty of people thru worse. :thmbsp: Good luck.

capo72 · Jan 3, 2007

Thanx guys, you are truely a wealth of knowledge. Thanx for sharing. Hopefully i'll tackle this project over the next couple of days.

Jeremy

rickon66 · Jan 3, 2007

I had the one that had the riveted switch and it looks completely different than the one in the link. It is a bugger getting into the front of the thing, but the results have been worth it. Good luck!!

capo72 · Jan 3, 2007

Well mine does not look like the one in the pics. I have attached a pic of mine. No wafer board on this one. Looks like all the wires are soldered to the switch. May be more of a challenge huh?

Jeremy

rickon66 · Jan 3, 2007

I took some pictures when I had mine apart, I'll see if I can find them and post them, they may be of help.

rickon66 · Jan 3, 2007

I did not remove the soldered wires and worked it in place, IIRC there is some slack in the wires. One other challenge is that it is ganged with the speaker switches and you don't want them to come apart as you work on the power switch. The rivets are soft metal and a pair of small nippers or side cutters will take off most all of the head. I used a small fine file to get rid of the rest of the head. I got #2-56 brass screws and nuts at a model railroadship to re-assemble, and even they were a little big. You can see in the picture that the copper contact post looks like charcoal. Good luck!!

TiberiuS · Jan 4, 2007

Apologies chaps, wasn't aware of the common problem. Thinking back I had a similar problem on an SX-424 or a 450 a couple of years back with the switch...just wouldn't power on.

A loose winding could cause a similar fault though, had it twice...on my center and on a portable I restored for a friend...ended up converting that one to take a little AC adaptor

Regards, TiberiuS

.

Strawman · Jan 4, 2007

Any help is appreciated around here. I've fixed more than one Adler calculator by tapping on the transformer with a hammer.

markthefixer · Jan 4, 2007

TiberiuS, no apologies needed, all input is welcome.... nothing beats experience...

rickon66: thanks for the pictures, I will link them in...

capo72: There is a wafer WITH WIRES in front of it, interesting, I can see it in the pictures. It should be easier to do without having to remove a wafer soldered to a printed circuit board. Plus the picture shows that the hardware mounting this part of the switch to the assembly is threaded. We have a BONA-FIDE subvariant of the riveted switch. Because:

Those rivets that go THROUGH the body of the switch are long, I would be interested in finding out how thick that switch is and how long the rivets need to be to reach through it (3/8", 7/16", 1/2" ???). rickon66's switch case had flat spots to allow really short rivets to be used.

Do you have a micrometer? Vernier dial gauge? Really good ruler (1/32"?) etc. That would help with the diameter of the replacements for the rivets.

I might be able to help with hardware, depending on how long those rivets are. (eyeglass hardware... got a bunch)

rickon66 · Jan 4, 2007

Mark.
Looking at capos72's picture I am pretty sure that mine was physically the same as his. The perfect size screw and nut to re-assemble would be a #1-64 machine screw. I used a #2-56 and had to ream out the plastic a little to make them fit. As far as length goes, go ahead and buy them a little longer as the are very easy to shorten as needed. The threaded pieces on the sides are what holds all the speaker selector switches and the power switch togeather.

capo72 · Jan 4, 2007

Mine is the same as Rick's. I got it apart tonight. I was able to rotate the post about 120 degrees, to get a fresh spot. I'll file the moving part to smooth it up. Maybe i'll get lucky and find some screws at work tomarrow. Mine does not look as bad inside as Rick's, so hopefully it will work OK. Thanx for the tremendous amount of help thus far. This is a great forum.

Jeremy

markthefixer · Jan 4, 2007

rickon66 said:
Mark.
Looking at capos72's picture I am pretty sure that mine was physically the same as his. The perfect size screw and nut to re-assemble would be a #1-64 machine screw. I used a #2-56 and had to ream out the plastic a little to make them fit. As far as length goes, go ahead and buy them a little longer as the are very easy to shorten as needed. The threaded pieces on the sides are what holds all the speaker selector switches and the power switch togeather.

My engineers eye spotted the difference, on your switch, the switch contact part of your switch had flattened sides indented into a round case, the flattened sides accomodated the short rivets. The mounting plate to the rest of the switch body was shaped like an oval with the threaded holes in the oval portion outside of the area covered by the round switch contact part.

His switch contact part of the switch appears to have a bakelite or plastic body that is completely round, with the rivets going through the thickness of the bakelite. :boring:

capo72 · Jan 5, 2007

The rivets are .070 diameter, and it is about 3/8" long, after I filed off the staked end. So I would guess 1/2" long should be plenty. I couldn't find anything smaller than 4-40 here at work, so I may swing by the hobby store on my way home for some screws. I need some small metric screws for my tone arm also, so that would kill a couple birds.

Jeremy

markthefixer · Jan 5, 2007

Ahhh, you updated your profile, we're practically neighbors, and I see I can leave the mechanical details of the rivet replacement in your capable hands.

The longest 0-80's I have wouldn't be long enough... for everyone else's reference 0-80's outer (unthreaded hole ) diameter is about 0.057 inch and the 0.070 stuff translates out to about #1 screws, or whatever metric....

just in case: www.fastener-express.com has 0-80 x 1/2" long, 1-72 x 3/4" long, 2-56 x 1" long and 3-48 x 1" long machine screws and nuts. I have used them successfully.

capo72 · Jan 9, 2007

Back in business!

Well I finally got it fixed, thanx to the wealth of knowledge on this board. You guys are great. I was able to rotate the stationary post of the contact to get a fresh spot, then I filed the pad on the moving arm. I got some #1-72 thread screws at a hobby store, and put her all back together. It's working great now! I did some cleaning while it was apart. The face and knobs cleaned up nice. The case needs some attention, so I plan to reveener it with some real walnut left over from a JBL project. Maybe i'll recap it someday, but for now i'll just enjoy it. Besides i've got plenty of projects lined up. Next is an SA-7800 with a weak channel. Thanx again guys. Some pics are attached.

Jeremy

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