Restoring Pioneer sx-1250

karel.b

Active Member
I started to restore my Pioneer SX-1250 last year, but my wife became very ill and I did not have time to work on it. Now that she is not too bad, I'd like to finish it.
I have all the necessary info (parts list) from MTF and MATTSD. The only thing that I have missing is any info on the tuner ass'y (AWE-068) semiconductors replacement, specifically the Q7-Q11 transistors (2sc1312 - Q7 and 2sc945 - Q8, 9, 10, 11).
Normally these transistors do'nt need replacement, but who ever worked on this unit before I bought it, bent the hell out of them. When I tried to straighten them, couple of them broke. I was going to replace them with ksc1845fta's or ksd1616agbu's, but being an amateur I thought I better ask for help.
Also the cores in T1 - ATE-029 (FM IF transformer) and T2 - ATE-013 (FM DET transformer) were totally broken. I have some cores from different pioneer board, but there are two sizes, 5mm long and 7mm long;(not aluminum!!), (one in T1 and two in T2.
I would be grateful for any help.
Thanks in advance
 
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q7 = 512-ksc1845...
q8 - q9 512-
q10 = 512-ksc2383...


Transformer answers will take longer, they are in a bottom box in a stack that has to be torn down to get to (I need to make something like a baker's rack for storage, and easier access) while I have a 9am Tuesday deadline to tear this place apart and rebuild for u-verse installation.. will lose internet sometime on Monday...

They are ate-013 for FM detector transformer
sx-750



-----------------------
and ate-029 for the IF transformer.


I will be editing in other model numbers that use the same transformers.
 
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Hi karel,

Hope your wife is feeling better.
How did the switch repairs go?
The sx-1250 & sx-1050 use mostly all of the same parts in the AM/FM tuner assy.

I was thrown off when "mtf" reported that the sx-750 used the same disc transformer, as in the 1050/1250 but as strange as it is, they used one (ratio detector instead of the quad-det in the HA1137) in this design and not in the sx-850/950.

Okay I am checking a AWE-067A, (sx-1050) "mtf" does not have to dig through his stuff!!

ATE-029 is a 5mm core and has white paint on the bottom
ATE-013 cores are both 5mm and orange paint on top
Of course they are of a ferrite material, aluminum core is usually only used for the LO as it is the highest frequency or lowest L.
Now it is totally out of alignment, so I will have to play with it to get it back in line.

Rick
 
Hi Rick,
She is feeling better now, but it is not over yet. Last two months was pretty much hell, but that's life.
The switch works fine, as far as I can tell, but I have to do more testing.
The 5mm cores I have are blue and orange. Is there a difference in the material they are made of? Or is it just the color. They are all made of ferrite as far as I can tell, but that does not mean anything. Hope it is the size that matters.
Now I've got to do the dishes!!!!
Thanks
 
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Do not be fooled with these ferrites, they may look the same but the materials can be different. Even the ones you have that are orange I can not say that they are for the transformers that you need, unless they are tested, either in circuit with signals or out of circuit with instruments.
You can try the orange ones in ATE-013 how ever.
I do suggest to look for a spare 750/1050/1250 tuner for parts. I think there is a 1050 on ebay from a guy I bought mine from in Toronto. I meet the guy as i did a pickup to save on $
I could offer to fix it, I would only need the IF pcb as I can inject the 10.7MHz IF from my generator, but that does not test your RF FE and it may need alignment.
Sorry to say you are in a up hill battle without being able to use instruments to test/repair the tuner.
 
I just sent a core to a gent in Sweden and it worked great. I have a few tuner boards, if you have remnants of the old and can provide measurements I can see what I have.
 
I second the motion to replace the whole transformer in each position.

A core donor would be useless after that, so why NOT send / swap the whole thing.

Then at least the setting would be close.

Do you have someone nearby that can do a tuner alignment?
 
Do as you wish, my offer stands.

I was thinking that once the appropriate cores come out, the donor is useless, and the cores have to come out of something with the appropriate frequency range and permeability. No less thread size and length.

The best alternative is to get the entire ate-013 and ate-029 transformer out, and, BK, I'd hate to see other transformers you have (which I consider to be a VALUABLE resource) "zorched" as their cores were removed and checked, and risk being interchanged. Those would be difficult failures to track...
 
If it makes any diff. I have an SX1250 parts unit, the FM board and all worked before I started parting it out, but the main var tuning assembly probably needs to go with it as a complete replacement .. if I take some parts from it , it's worth less.
Replacing cores, xistors etc needs realignment of the FM section ..
My .02
John M
 
Hi everyone,
I totally appreciate your input and help. Nothing is as simple as it seems to be.
But before I can even try to test the cores that I have, I need to replace the 5 transistors in the board. Without them the board is useless. So far I only have replacement for Q7 and Q10 from MTF.
Thanks
 
John M has made a generous offer, I suggest to jump on that and get the necessary spare parts (IF unit) or simply just replace the whole IF unit. Using a new/diff IF unit will hopefully work fine, as is, and not have been taken out of alignment.
BTW the 1250 has separate RF FE and IF units, I see them sold separately all the time.
There is also one for sale now
http://www.ebay.com/itm/Pioneer-SX-...954?pt=LH_DefaultDomain_0&hash=item3f45539fd2
 
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I would include all you need .. I have no use right now for this ..
anybody (MTF) reading this thread I also have the 2 amp sections (stock) that work.. heat sinks are a little damaged but the amps worked...

Good luck with your project .. these SX1250's are worth it ..

John M
 
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Here is one for you Mark, the anti-birdie filters are adjustable, (F5/6 on sx1050,F6/7 on sx1250) but the SM does not say how to adjust them, any idea?
It says on p21 it is a 200KHz trap, so one must modulate a FM carrier at that rate or inject a 200KHz sinus signal it into the detector output at pin 12 of awe-068, then scope at c26(1250)/c42(1050), adjust for minimum 200KHz output.
 
Well, this was before HD broadcasting on FM (which uses 129khz - 198khz at up to -10db (-20 old max, -14 current usual max, -10 special max) referenced to the carrier) so they must have been aiming at the adjacent channel interference.

Nowadays a LPF cutting off at the upper sidebands of the Stereo signal might be a good idea.

IF we're gonna split hairs. :D

Might be instructive to run the detected output into a spectrum analyzer...

In answer to your question: 200khz sine into the lifted minus leg of C23. :dunno:

BUT 114khz and 190 khz are 3rd and 5th harmonics of the 38khz .. And don't forget the 67khz SCA...
 
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Hi all,
Again, thanks for your avice and help, but my question about the transistors is still unanswered. If someone would give me a hint what transistors to use (Mouser cat. #), I would be very gratefull. Other than the transistors, the board is in good shape.
Thanks again
 
Yes, as I mentioned before that is where I've got most of the information, plus the one from MTF. BUT, there is no info on AWE-068!!!(tuner ass'y).
Thanks
 
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Yes, as I mentioned before that is where I've got most of the information, plus the one from MTF. BUT, there is no info onAWE-068!!!(tuner ass'y).
Thanks

Most say not to fool with the tuner if it is working. Replacing parts on it will lead to a realignment and that takes special tools and skill.

If it works leave it be.
 
It's the tuner muting relay system that took damage. The transistors are physically toast.

so

q7 = 512-ksc1845...
q8 - q9 512-ksc1845...
q10 = 512-ksc2383...
q11 = 512-ksc1845...

If you bought a quantity to get a price break, you should be in good shape.
 
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