Another Pioneer sx-1000tw redo.

anderslober

Yikes...not again!
Hello Forum.....I am restoring yet another of these nice units. This unit has a couple of problems. Stereo light will not come on(bulb is new) and at turn OFF there is a kinda' power-down crackling in both channels. Power ON is fine.

Could the crackling be a PS problem. I have just changed the caps...not the tr's. I don't have any of the recommended ztx695 or ztx795 tr's. Can other subs be used? Mje15032?


The stereo light does not come on(bulb is new). I have 21.4v on pin11 from PS....both sides of the r36 resistor have 21.4v(should be 23v/18v)......and the IND pin on MPX board has the same 21.4v. Is the resistor bad?

On c717 MPX board I have 5.5v(+ leg)....and when I tune away from stereo, I still get 5.5v.......so, I guess I there is something amiss. Sound out put is fine. Also r733 measures a constant 3.1v..(pin6 T702).......it should be 2.7v mono/0.5v stereo.

Another thing.....when I turn the unit OFF, I get some awful crackling in the earphones(only earphones at the moment...don't want to blow speakers)...what could cause this 'turn-OFF-crackling"?

Also...the MPX board is choke-full of 2sc458 's.(all except one 2sc870).........On the scat' it says all the tr's should be 2sc870 's............should I change those dreaded 2sc458 's?

Reg. The above info....I posted it in an older sx1000tw thread.......probably shouldn't have done that....sorry.:)
 
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DeOxit the hell out of ALL of the CONTROLS 1st!!!!!

Hello Forum.....I am restoring yet another of these nice units. This unit has a couple of problems. Stereo light will not come on(bulb is new) and at turn OFF there is a

Possible, but I'm leaning more to the output coupling caps. Parallel a DC Voltmeter across the spkr terminals(with spkrs attached) and watch for DC voltage spike when you hear the crackles. .


The stereo light does not come on(bulb is new). I have 21.4v on pin11 from PS....both sides of the r36 resistor have 21.4v(should be 23v/18v)......and the IND pin on MPX board has the same 21.4v. Is the resistor bad?

Lift one end of resistor and test it. replace if out of spec.

On c717 MPX board I have 5.5v(+ leg)....and when I tune away from stereo, I still get 5.5v.......so, I guess I there is something amiss. Sound out put is fine. Also r733 measures a constant 3.1v..(pin6 T702).......it should be 2.7v mono/0.5v stereo.

Another thing.....when I turn the unit OFF, I get some awful crackling in the earphones(only earphones at the moment...don't want to blow speakers)...what could cause this 'turn-OFF-crackling"?

Put a cheap pair of speakers on it and with the volume down listen for crackling and watch the DC Voltmeter

Also...the MPX board is choke-full of 2sc458 's.(all except one 2sc870).........On the scat' it says all the tr's should be 2sc870 's............should I change those dreaded 2sc458 's?

The replacement for the 2sc870/2sc871/2sc458 are all the KSC1845 Replace on all boards they are on.


Reg. The above info....I posted it in an older sx1000tw thread.......probably shouldn't have done that....sorry.:)

I don't know about the Zetex replacements.

I'd Replace the Main Filter caps(C12,C13) with at least 2200uf /100V and the output coupling caps with 2200uf / 63v.

The MPX board is probably gaffed by the 458's. It'll need an alignment anyway, so the worst it'll do is flip you the bird. At best it'll work.

Break out your signal tracer and see if you can track down the offending culprit(s). It doesn't have preout/main-in jumpers so you can't separate the preamp from the amp.
 
Thanks Larry.....will do! I replaced all caps. The coupling caps are 1000uf/100v and the filters are now 3300uf/100v 's.
On the power supply......would mje15032 's suffice?(to cure power off crackling). They definitely over-spec the originals. I probably should change the diodes too......1N5404's....x6.
I tested the r36......it was fine.....it is 680 ohm.......measured 682 ohm....

Voltage on c717?..........it stays at 5.5v...........
 
Here are my PS voltages:

Pin4---0.0v.........ok.
Pin5---80.3v..........bit high.
Pin6---28.9v..........bit low.
Pin7---35.2v..........bit low.
Pin8---12.6v.......ok.
Pin11--21.6v.......bit low.
Pin12--0.0v........ok.

2sc627-----ksc3503.......ok.....will change. How about the other 2 tr's on PS? Same?
 
Scrap the 3503 listing.....I'm 1/2 asleep right now and this 12 year old laptop is acting up.


preplace all 3 with the ztx694b mouser has them for 95 cents ea.

Onsemi shows 2n5550G as direct replacement for ztx694B. I'd be real hesitant putting the mj15032 in there....

Check D706. Also R713,715,R716. If those check out it's got deeper problems than you and I can troubleshoot.
 
Ok....I got hold of some 2n5550 's. They seem puny compared to the originals, which have big heatsinks. Will there be a heat problem? Larry, why would you hesitate to use the mje15032's? They were recommended in another sx1000tw thread by MTF.

I will also change all the diodes.......6x 1n5404......and a 13v zener. This should make the PS super-fresh!

If the unit still makes the power-down-crackle.......then I will start changing all the tr's on the amp board.
2sc538........ksc945........other?
2sc627........ksc3503........2n5550.....ksc2310....?
2sc485........ksc2690......?
2sa537........ksa1220......?
2sc458........ksc1845.

All the above subs were gleaned from other threads................I just need confirmation......thanks
 
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No experience with them and the operating freq ddn't look right to me. If MTF says yes to them in a 1000TW, go for it.

As for the 2n5550's, OnSemi lists them as direct replacements. Spec's are close, and possible that heatsinks aren't needed on them.

Again. If MTF said use the MJ15032's who am I to argue.

What's your wall voltage? the 5404 is only rated to 400V. If your wall voltage is 220, I'd use a 5406. (rated for 600 PRV) if it's 120 a 5404 would be fine. I was reading in the tube forum or even here, that in case of Rect diodes, 2.5 x wall voltage should be minimum size to allow it to handle spikes, etc. Good insurance? Possibly.
 
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Thanks larry...please check post #9 again...i edited it a bit..........

I will use 1n5406 for the diodes......voltage here in Sing is 220v/240v........
 
Seeing that you have another 1000TW inhouse (the one you did over last winter), compare that unit with this unit for the transistor subs. Might be the best way to go if the 1st unit is working well. Just duplicate the parts into the new unit.

On the 2sc627 use the 3503 or the 5550 with a clip on heatsink. I could verify all but the 2sa537.
 
These are my final intentions(unless a guru disagrees!). I compared A LOT of datasheets.

Power Supply:
2sc486 ....... ksc2690.
2sc627 ....... ksc3503.
2sc620 ....... ksc2690.


Main amp:
2sc538 ....... ksc945.
2sc627 ....... ksc3503.
2sc458 ....... ksc1845.
2sc485 ....... ksc2690.
2sa537 ....... ksa1220.

I will install.....................................and see what happens.
 
I recently re-build one of these and had a bit of frustration, so FWIW...

Check the big sand cast resistors on the output caps and the main filter caps closely. You want those to be close to expected values.
 
I will soon be back working on this nice unit again. I intend to change all the 2sc458 tr's on the MPX board, in the hope this will cure my stereo light problem.

The spacing of the rca connectors is very tight. What kind of 'slender' connectors can you fellas recommend. The rca's I use at the moment are completely normal/cheap rca cables, but they are quite hard to fit into the units' rca connectors....
 
I use the normal cheap Ratshack types, but have to trim one or two sides down almost to the metal to get them to fit. either that or find some OLD stuff.
 
60's style have really small diameter jack covers, and very few if any ribs or nubs to grab on. Hard to find unless you get them with the gear. You could also remove the covers from the ones you have now and give the outer shell a couple coats of liquid electrical tape after a wrap or two of Electrical tape to seal the tape.

I've got the same problem with my 1000A (close together) but with those plugs with the flare on the ends that don't allow the jack to sit all the way in. I've taken the jacks and removed the covers, put a wrap of tape on them, inserted into the plugs and tack soldered to the plugs until I can get a new board with current RCA's made. There ain't a lot of room on the back of the 1000A either, to make mods. So far it's working as long as I don't move anything.
 
Ok....I am back with the 1000tw ..........I decided to hook-up some speakers and see if the turn-off-crackling was there......well......it wasn't! "scratch head'........Only crackling through the earphones.......huh?......what can this be? New resistors?

Otherwise the unit plays fine! Still not able to get any light out of the stereo light....any ideas? I have a feeling a tr or diode on the MPX board, isn't doing what it is supposed to do. Would it be a good idea to change the 2sc458's anyway?

I get a strong FM signal...........vocals and news is nicely placed in the middle....so, i think stereo is working........


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