Pioneer SX-1250

[xXColdShotXx]

Pioneer SX-1250 popping and cracking on L side, very lil sound on R side

Hello,

I have a pioneer sx-1250 and i put it in the shop and waited 4 or 5 months for the tech to fix it, but everytime i called him he said he was so backed up he still hadn't gotten to it. I got tired of waiting so i went and picked it up and he told me the tone board needed redone, and that i could use it for a pre-amp or power amp, just not together, so i tried what he said and it didn't work, and when used as pre-amp there is no sound from either side to my external power amp, when used normally 1 side plays at normal sound and pops and scratchy, the other side barely plays any sound at all, and when i turn the tone switch off there is no sound at all from either channel. I am going to hook it up in a few minutes to see what all it does and doesn't do and i'll add it here if anyone wants to give any info it'd be greatly appreciated, thanks in advance

 

[Urizen]

Moved to the Pioneer forum for more exposure.

Welcome to AK!

 

[xXColdShotXx]

Thank You, Urizen

 

[Bob91343]

It appears that some serious investigation with generator and oscilloscope is in order.

You might measure the voltages on the various circuits and compare to the figures in the service manual, on the schematic diagram.

 

[markthefixer]

I can talk you through a rebuild of the tone board - excluding shipping you should get away with less than 10 bucks worth of capacitors and transistors.

It requires opening up the top and bottom and pulling the decorative faceplate to get to the board, then replacing the components.

After that we can re-evaluate OR we/you can do the flat amp board (similar) and (either way) deoxit the switches thoroughly while it's open.

 

[slow_jazz]

Sounds like a big case of Deoxit is in order.

Mine acts up if I un-push the 30hz button...

 

[xXColdShotXx]

thanks mark i am gonna get a dmm (if i can find a decent 1 around here) what's a decent 1 to get around $30 to $50? I'll be so glad to get this stereo working again to rattle the neighbors windows. hook this receiver up with my yamaha mx-800u and i'll be ready to rock.

 

[xXColdShotXx]

Mark, could you make a parts list for me to get for the tone board? thanks in advance

 

[xXColdShotXx]

Took the ol' 1250 apart today and cleaned all the dust and stuff out of it, while i was at it i looked at the tone board and didn't see any burnt marks, but i noticed an assessive amount of lube type stuff on the metal cover and circuit board, should i clean all of that back off? and i noticed the 2 back big caps had cracks in them, but no leakage, yet. if you wouldn't mind, could you make a list of stuff i need for the tone board rebuild, markthefixer? thanks in advance

 

[EchoWars]

Sounds like either the tone amp and the flat amp both have issues, or the unit has a bad case of dirty switches. In either case, I'd not start my analysis of the problem from the opinion of another tech.

 

[xXColdShotXx]

Thanks for your input, echo, i am going to get a deoxit kit soon and do the switches and pots, i am new to repairing electronics even though i have always liked hooking up a/v equipment, hope to learn all i can from you guys and i really appreciate any help that is offered.

 

[markthefixer]

The tone board is the AWG-041 control amp.

There are a BUNCH of recent threads containing the 1250 parts lists, should you look....

this already posted zip file has the capacitor numbers to order from mouser.com, download it, unzip it and open it up, it is in the excel format.

http://www.audiokarma.org/forums/attachment.php?attachmentid=234844&d=1286786433

Then there are 4 transistors on the board, four 2sc1312, replace them with :
512-KSC1845EBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

you have to clean the pots thoroughly with deoxit and then faderlube, and the switch with deoxit and progold.

You need to do this to ALL the pots and switches FIRST, before ordering parts, we have to figure out what's wrong WITHOUT chasing GHOSTS caused by dirty switches.

Then we'll talk about further work.

post pictures of these "cracked caps"...

edit - was writing this post, took TOO long finding where I posted that damn zip file... two posts appear while I'm digging...

 

[xXColdShotXx]

Thanks, Markthefixer, after this project if all goes well would you be interested in helping me with a spec 2 power amp?, I'll get the pics on tomorrow, Would Radio Shack cleaner/lube work in place of deoxit and faderlube?

 

[xXColdShotXx]

i just hooked the 1250 up and tested it and i was wrong, when i turn the tone on the sound cuts almost all the way off, but it still pops and cracks out of the left side, the right side doesn't pop or crack, when tone is off it has more sound out of the left and is breaking up constantly and no where near normal volume. barely any sound coming out of the right channel, still pops and cracks out of the left only with tone off.

 

[aussiedan]

Thanks, Markthefixer, after this project if all goes well would you be interested in helping me with a spec 2 power amp?, I'll get the pics on tomorrow, Would Radio Shack cleaner/lube work in place of deoxit and faderlube?

Don't make the same mistake I did by suggesting other cleaners.
Get some De-Oxit. You wont regret it.

It can be a bother to get (I have to wait 1-2 weeks for mine) but its worth it.

You can use the Radio shack stuff on your car engine.

 

[xXColdShotXx]

the rs cleaner/lube is flammable too, i'll get the de-oxit kit since everyone is suggesting it.

 

[markthefixer]

Cleaner leaves you with CLEAN CORROSION... which can be good because the deoxit can get AT the corrosion - but D-5 is 95 percent cleaner and 5 percent deoxit.

deoxit lossens the chemical bonds between sulphate corrosion and the clean metal, which then contact friction can scrub it away.

 

[xXColdShotXx]

I've got a problem here, was looking up the parts i needed on mouser and noticed in the parts list that there's a difference between 2 caps with the same numbers except the volatage, 1 has 10v and the other is 16v with same part number # 647-UPW1C101MED

 

[xXColdShotXx]

Here's a pic of 1 cap with the crack in it, other looks about the same as this, but with smaller crack and neither of them have any signs on leakage


Here's another pic of a component, looks to be a burnt mark on it

 

[markthefixer]

No mistake there... 16v cap works fine in a 10v position. differences in size or cost can be minimal (for us, manufacturer's bean counters would be indignant), thus making stocking/quantities the driving factor.

Those are the vents, and the material over them may be thinner and more easily dried out.

IF you want to pursue tests on the caps themselves to check them, ask...

but even that wouldn't necessary pinpoint a cap the "only puked a little" and was cleaned up afterward.

re-second pix - rub mark?? i wouldn't be worried.