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Another 939 rebuild thread

Fantastic work Larry! In the best spirit of AK you took the time to share your work with folks so they (at least the more skilled or adventurous of us) can learn along. Glad to hear it all turned out so well!
 
MANY THANKS To SCHMIKKA for the 939. I don't really know what i did or how I deserved this "gift". Thanks ED!

And to UncleBort :thmbsp:(Tom):thmbsp: for the SX-1010 parts. Thanks TOM!

Both of these guys epitomize what AK is about. Sharing Audio with others.

I've got it hooked up to my Technics SL-1200 MK 1 listening to DSOTM. No hum, no hiss. DEAD QUIET even on the entrance ramp on the record. Exit ramp the same. I realized I have a couple lights out, so off to DGWOJO I go. I gotta pay for something on this receiver. LOL! Between Mouser and Yesterdays Audio, I've got about $135. into it. Not bad. It actually sounds better than my 1010 did.
 
It's been about 27-28 hours now(8:00pm Eastern) on the 48 hour run in. It's starting to tighten up in the bass and the mids and highs are typical PIONEER. Sound stage is larger than before the recap and seapration is outstanding. In phono on dead wax it's dead QUIET! Interstation hiss in FM (muting out) is minimal if any. AM interstation is quiet. No whistle as you go off frequency. Center voltage is holding @ .01v and .02V with Bias of 50mv rock steady both channels. It's a little warm but no more than my 1010 was, and actually about what my 737 runs at. Switches and rotary controls are operating without noise. I get more noise from the ball bearing click on the stepped controls than I do from the speakers.

Mechanically, without it going on a scope, I'd call it a 8. Really should scope it, but finding someone with one that knows how/wht to do with one.............One of these days...(I said the same thing 3 year ago too). The Bank (wife) just shut down the access to funds so the cabinet will take longer. Why doesn't that surprise me.
At least I can kick back and listen to one of the BEST OF PIONEER!

Larry
 
Sounds like a keeper Larry. I take it you're sticking with incandescant lighting since you mentioned Dgwojo. Ever consider LEDs? I only ask because against that black face, they really bring out the blues.
 
Not fond of LED's, or CFL's. About the only led I use is in my MAGLIGHT. Certain things I stay away from......LED's, DVD's, Anything audio that's Digital, any phone that has more than 10 keys and takes a Master's to turn the thing on....or a 3 year old.

Incandescents for me are easier, cheaper usually, and I can replace them in my sleep without my trifocals.


Larry
 
I hear you. I was reluctant to try them for some of the same reasons. Cost is a big one too. I took the plunge with the fuse-style in my 838, figuring I could easily swap them back if I didn't like them. So far, I like them. Brings new life to a dial with old paper (vellum). I wouldn't use them for everything or even most things, but the Pioneer and Marantz black face, blue letter dials look nice with them (personal opinion of course) as long as they're not too bright. I absolutly run from CFLs.
 
Wow that is Epic, Congrats on the successful restoration, I thoroughly enjoyed and learned a hell of a lot from this thread.:tresbon:
 
MAXZ28 said:
I don't know why but I'm kind of digging that power switch....like an ignition off a vintage automobile. :thmbsp: It probably was a shop stereo - they probably installed it so only the foreman was the only one who could turn the stereo on or off.
Click to expand...





Looks like a key that I use on my boat:yes:
Larry thanks for taking the time to share this rebuild. The photos are especially nice, I notice you used "scrubbing bubbles" to clean the inside is that the same SB I would use in the shower? Can you elaborate just a bit on what you used after the SB? I would have never thought of baking a receiver although I do dry the bolt assemblies of old rifles in my microwave after scrubbing them clean of dried grease.
I have a 939 that is distorted in both channels and sounds like the sound is coming out through several layers of blankets. It also has a vinyl top. Believe it or not I have a SA9800 that has a vinyl covered "wood" top.........cheap finish for such a fine am

ETA I misspoke. I have a 939 not a 950. Your guide will help me if I ever decide to get into it.:scratch2::scratch2:
 
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Same Scrubbing bubbles. Spray it on, and brush it around. Heavy on the chassis, light on the boards. I rinsedit with a can of CRC QD Electronics cleaner. Let it air out an hour on a fan, then bake @ 170* or lowest setting in oven for 3 hours or so. Make sure the transformer access holes are UP! Lets out the residual moisture/steam. (Learned this one from tube gear) Let sit with a fan on it for 2 days. Then start it up with a VARIAC AND A DBT ON IT. If no problems, switch to wall voltage.

Larry
 
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Thanks Larry I have a filthy 1250 that's covered with tobacco smoke residue inside and out. I've cleaned the knobs and face plate......I have to replace the glass (any experience with this??) and reassemble the wood cabinet, now I'll clean the inside. I don't have a variac
 
If you have the major pieces of the glass around the tuner knob, take that and the faceplate to a glass shop and have them make a new piece. Lexan would maybe be less expensive and more durable.

If you don't have a variac, then just use a DBT for the 1st power up. It'll let you know if there is a problem right off. No less than a 100W bulb. Probably a 150W would be better for a 1250 but never seen one in the flesh.

Not a fan of the x50 and x80 series aesthetically. The X90's I do like. It's the contrast in the dial.

Larry
 
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Thanks Larry. I saved several pieces of glass and I've cleaned out the channel. I can find a shop that will cut the glass but I'll have to look for a plastics shop for lexan. I'm a fan of the front appearance of the 1010 and it's cosmetic twins. I bought the 1080 off e-bay and it was a complete disaster....damaged in shipment and nothing at all like the seller described. My CC company refunded all costs and filed a chargeback against paypal/e-bay. I refused to ship it back so it's just sitting here waiting for someone to work on it. If anyone here wants one in this condition they can have it but they'll have to pick it up. PM me anyone.:thmbsp:
 
I have a 150w bulb and 200w bulb for really big receivers like the SX-1980. They are big, as you can imagine.
 
Great thread, awesome rebuild... I have a question as it's not entirely clear to me, and I haven't completely RTFM'd. Are the matched KSA992 selected for gain or for voltage? Just got an SX-939 with all its crackling goodness so I want to get into fixing the PS and main issues first...thank you to everyone who has posted all of this great information.
 
mainly gain. if your DMM has a hFe function on it, that's good enough for what is needed.
 
General consensus is to repair the crackling 1st (ie: replacethe 2sc1451 and 2sa725/726 on the amp 1st), test and continue on each board working back. Once it's fixed, THEN do the upgrades.
 
Thank you, that is my plan!

Oddly, opening it for the first time, I find that the 1451 and 809s have already been replaced with NEC 381 and 536. The PS still has 313 and 507 and I can see some 725 here and there. Was there a factory version which came with 381 and 536?
 
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