have a lead on an SX-750, but...

[Nick_the_'Nole]

I may be able to score a free SX-750 in the near future, but with a catch. The thing won't power on fully, it just makes a faint crackling noise and the panel lights flicker on and off. It doesn't seem to be just a dirty power swtich, since it does the same thing in all positions and with working it back and forth a bit. Now, if the thing's free, I can't turn it down regardless, but just so I have some direction, does anybody have some ideas on what sort of headache I may be inheriting? I'm really hoping it's not a fried power tranny...

 

[Fuzzy Lumpkins]

I have a SX-750, SX-450 and a Project One Mark IV with
those same symptoms and all were fixed by thoroughly
cleaning the power switch. Just my experience though.

Good Luck

 

[Strawman]

Cold solder joints? :scratch2:

 

[B3Nut]

Crackling + flickering panel lamps = bad power switch. The power switch is switched to "on" at the first click and further rotation of the speaker switch doesn't move the power switch any further. I'd bet the contacts are pretty well eaten up, find a donor unit for a switch if you nab this puppy.

Todd in Beerbratistan

 

[Nick_the_'Nole]

Alright, that's a relief, at least it should be a relatively easy fix. Hopefully even some Deoxit will work that out. I was just worried it might be some expensive overhaul coming. Makes sense it would be a dirty swich, I guess, it has been sitting on a shelf behind a couch in an unairconditioned house for years...

 

[agger]

The power switch may not only be dirty, but worn out. Then it can't be fixed by cleaning, you need a replacement from a parts unit. I think there are no more new replacements availabe. or you bridge it and use a switchable power distribution or a nice pioneer timer to do the job.

 

[stereofisher]

Grab it!!

Sounds like a bad power switch. Go for it. Free is Good! Eric

 

[Nick_the_'Nole]

Yep, free IS good.

I actually doubt it's worn out, I remember it working within the last year and it hasn't seen much, if any service since then, so it more than likely is just dirt and corrosion...

So now it's just a matter of convincing 'em it doesn't work so they'll let me have it without any fuss.

 

[markthefixer]

Common problem on those pioneers. Pustelniakr has done this repair before and deoxit wont cut through burned contacts in the alps switch that is used.

They are REAL contacts that can be disassembled (pita to get to tho) and burnished for like new performance for years to come.

I had a picture up, then took it down, of an sx-550 switch disassembled to show the contacts...

this is a link to the after action report on Rabbi Rich's work on that sx-450.

here is the picture again. I pulled it to save space here.

 

[Nick_the_'Nole]

Oh, that looks like an easy fix. Helluva lot better than the switch on my old SX-1500T, which is one of those standard rotary deals you can't easily disassemble. I finally picked up that receiver tonight, and I don't feel like going to bed, so I'ma work on fixing that, see if I can't get it going by sunup. Hopefully I'll be able to give the first couple floors of the dorm a nice wake-up call...

 

[markthefixer]

hey.... I can hear the swearing all the way over here!!!!!!!

I said it was a pita.

Seriously..... How did it go???

I took apart a sx-550, so if you have any questions, (or shudder....break any parts...) give me a holler .... but rich may beat me with a reply!!!

 

[Strawman]

If it were easy, a monkey could do it! How's it coming? Break out the camera.

 

[GibsonLesPaul]

If it were easy, a monkey could do it! How's it coming? Break out the camera.

Alright, you got me. Guess I'll go back to selling shoes........ :sigh:

 

[Nick_the_'Nole]

Got it working perfectly. 'Twas indeed a royal PITA, but luckily the contacts were still good under the buildup of crap on them. Took about an hour and a half to do, total, and I think getting it back together and back in the receiver was the tough part, not a whole lotta room inside those things...

I would already have snapped a bunch of pics, but alas my digital camera seems to have taken a crap. In retrospect it prolly woulda been a good topic for a picture tutorial. The receiver itself exactly the same as basically every other SX-750 tho, except that it had a literal 1/4" thick layer of dust inside and out. Still don't have it completely cleaned up, and some of the other controls are still scratchy, but I'ma wait and get some Deoxit for those. It's in great shape other than the dirt, though, couple little nicks on the wood panels but otherwise pristine.

I'm stoked, this is a true "score" even though I hate that word now. Thanks for the advice everyone. :thmbsp:

 

[markthefixer]

:thmbsp:

Congratulations... that IS an accomplishment.

 

[Strawman]

Glad to hear you got her going.

 

[Brockster]

Glad this thread is here. Now I know why my SX-750 ($10 garage sale) is spazzing when I turn it on...

 

[vwap]

I hate to revive an old thread, but I figure it's probably better than starting a new one on the same subject...

... So how do I get the power switch out?

I've taken the faceplate off, desoldered the pins on the wafer, but there still must be something I'm missing in order to get the pot out completely. From the looks of it, I'm thinking I have to take the the dial frame out, as well, from the SX-650 service manual? Is this correct? If so, is there any way to do this without screwing up the tuning assembly and needle?

Thanks for any tips.

 

[markthefixer]

The switch body itself can be disassembled - in situ -

BUT isn't there about an inch of clearance behind the switch?

Take pictures, and start a new thread... it's worth it....

here is a link to the old threads

note that BOTH ends of the rods holding the switch together are threaded.

Remove the nuts on the wafer end of the rods, then the spacers. Loosen the panel mount.
This will allow tilting it up to get the wafer pins out of the pc board and then slide the wafer off
Then slide off the power switch. Some power switches are held together by rivets,
So FIRST you will need some small screws to put it back together.
Hobby store.. 4-40 is too big, #3 or #2 screws... take it with for matching size and length.

first:

next:

Close up:

 

[vwap]

Done! I ended up taking off the dial frame by carefully working the tuner rope out and above the frame. That and unscrewing the back of the posts so the wafer could be tilted.

Couldn't've done it without your help!

Thanks!