Brought Home A SX-1980 Planning a Restoration.

Discussion in 'Pioneer Audio' started by Fhamre, Sep 29, 2017.

  1. Fhamre

    Fhamre Super Member

    Managed to get my FM working quite well after cleaning the tuning capacitor.Not sure about Quartz lock. It does light up on occasion. But more research needed.
    I have recapped the whole unit and replaced all the recommended transistors. Will replace the PS caps last.
    I did build two CS boards. They test as a diode on my Peak. Is there a way to confirm they are built properly before installing?
    Need to figure out exactly how to install them.
     
  2. Fhamre

    Fhamre Super Member

    Looking for hand holding guidance as to which components get pulled and exactly where the two cs mod boards get installed.
    I have this 1980 running quite well and would not like to screw it up at this late stage.
    Perhaps one could indicate on this photo.
    55.JPG
    Can one also test the boards before installation to confirm correct wiring?
     
  3. Fhamre

    Fhamre Super Member

    Well just need a little clarity. I found these two pics that MTF put in an older post to show where to install the two current source boards.
    I was able to test my two boards with a 9V battery and the diodes light up thus indicating the boards are properly wired. So now just some assurance that as per the pics I remove the FET, along with two diodes and two resistors/ location.
    The pics suggest I have a choice as to where to install the positive and negative leads. Am I correct in this?
    neg_reg_AK_post.jpg pos_reg_AK_post.jpg
     
  4. zebulon1

    zebulon1 Back repairing the PL's Subscriber

    Messages:
    3,995
    Location:
    Las Vegas Nevada
  5. Fhamre

    Fhamre Super Member

    Well the cs mod installation went well. Checked the DC offset and bias again. Now next up replacing the PS caps.
    Another quick question. One of the original relays had a small magnet glued on each side of the relay case near the contacts.When I replaced the relay at first I didn't put the magnets back in and all worked well. I had a change of heart and put them back in just to keep it as original. First time I have run across magnets attached to the exterior of a relay. Is it recommended to keep the magnets?
     
  6. kevzep

    kevzep Its all about the Music Subscriber

    Damn, can't believe I missed this!!

    I never put any magnets on the relays of the 1980 I did, the chap I did the 1980 for then sold it for horrendous amounts of money to someone I know, and its happily running as a daily driver...

    Are you going to relocate the regulators to the main heatsinks, I feel its very necessary, after monitoring the temp of those regulators, I felt a lot better getting them on the main heatsink where they run a lot cooler. I put the +/-80V and the +/-30V regs on there, I only moved the 80's to start with, but monitoring the temp of the 30's, they were running at 70˚C (158˚F) which I decided was way too hot to be on that PSU board.....
    My theory is those boards are all a bit cooked by now, so to save any more damage, moving the heat away is the way to go...

    I can probably help you with the quartz lock, I had a problem with the quartz lock on the one I did, turned out to be pretty simple.
    The procedures for dialing in the quartz lock is not very complicated....as long as that's what it is....they are a complicated tuner, and one I actually like...
     
  7. Fhamre

    Fhamre Super Member

    I didn't quite finish the ps cap replacement,today. But if all goes well I will explore moving the regulators. I believe it makes too much sense not to do.I will see what I have for fan connectors.
    Re the quartz lock feature. Isn't the knob required to be installed in order for the feature to work correctly? I believe I tweaked the quartz lock feature on another unit the model and make I can't remember. But always welcome advice.
     
  8. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    20,626
    Location:
    Bensenville,Illinois
    They wouldn't spend the money for the magnets if they wasn't necessary.

    That setup (magnets affixed to the protect relay at the contacts) is for MAGNETIC DC ARC QUENCHING.

    You have a better ability to interrupt AC current with an air gap because AC goes to zero volts every cycle.
    DC arcs have more staying power. Larger gaps are needed to interrupt the circuit when current is flowing.
    Their Achilles's heel is the magnetic field they develop - so the magnet stretches the magnetic field of the plasma cloud sustaining the arc.

    USE THE MAGNETS. period.
     
    Last edited: Oct 10, 2017
  9. Fhamre

    Fhamre Super Member

    What he said!
    Thx Mark.
     
  10. kevzep

    kevzep Its all about the Music Subscriber

    Of course, you are so right, the one I did obviously had them removed, I never saw them....So I just installed the new relays as they came.
    Thanks Mark for the explanation.
     
  11. kevzep

    kevzep Its all about the Music Subscriber

    Its a little bit of work moving them, but well worth the effort. You'll get more trouble free miles out of it with them relocated.

    the knob is best on because it completes the correct mass for the touch switching. It is possible you have one where apparently, and Mark can probably verify this, made the sensitivity of that touch switch adjustable.
    Or it could be the quartz lock circuit needs a tweak....
    But however, I did mine with the knob off and it didn't seem to make any noticeable difference, you just need to touch the shaft instead of the switch........but you could just slip the knob on just for that purpose.
     
  12. Fhamre

    Fhamre Super Member

    Well moved the 80+/- regulators . That went well enough. At some point I may move the 30's. But I'm out of fan connectors.
    The fan wires seem a little thin. But they seem to do the job.
    Would appreciate a little quartz lock tweaking advice,thx
     
  13. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    20,626
    Location:
    Bensenville,Illinois
    A little quartz lock tweaking advice.... hmmm......

    Don't do it.

    Very few people do tuner work, even far fewer on the quartz lock.

    MANY possible factors can be interfering. Center tuning of the discriminator, gain of the RF / IF stages, discriminator tuning which is different than center, yet somewhat related. Severa; adjustments INSIDE of the APC box, which has to be opened - and isn't a good idea.
     
  14. Fhamre

    Fhamre Super Member

    Well I am in testing mode. The odd pop in the volume control as it clicks at low volume. Will likely have to remove that pot again and go at it.
    FM and Quartz lock seems to work fine for about 5 minutes then drops the station. Readjust it and it seems to stay locked and never drift for hours. But two days in a row I would set the lock and station only to have it disappear within a few minutes. Set it again and it seems to stay locked.
    May need to go in and clean the variable cap again.
     
  15. Fhamre

    Fhamre Super Member

    Forgot to mention. The tuning section is the only area I haven't recapped.
     
  16. kevzep

    kevzep Its all about the Music Subscriber

    Really, there could be as Mark says a few things at play here. Diagnoses for the fault is the critical thing here as you do not want to be in there with the golden screwdriver tweaking things which do not need or never need tweaking.

    Someone may have already been in there with the golden tweaker, making things "better"..... this is where experience comes into it to decipher what may have happened in a previous repair or whether its a new fault.

    You could just check all the voltages to the APC circuit to make sure nothing is missing, they can be measured without taking the cover off the APC if I remember correctly, there is a 5V supply which powers the crystal oscillator on that board, this was the issue with the one I did, but my symptoms were a little different than yours, but it doesn't mean to say something hasn't gone flaky in there...there's even a relay involved in the APC as well, its quite complicated.
    But like Mark says you have to open the APC box and if you haven't got a lot of experience with tuners it might not be a good idea. You might end up making it worse....
    The tuner in the 1980 is very complicated and even for a tuner guru they can be a challenge especially with this sort of intermittent type fault.

    After having a think about it I can't recommenced going in.....

    I got lucky with mine!! It was a straight forward supply issue.
     
  17. Fhamre

    Fhamre Super Member

    Are you recommending not recapping? I am in not a position to do an alignment nor situated near some one who can if need be.
    I can see the tuning section is complex. I don't usually recap a tuner board unless necessary.
    Right now the the unit will sit 24 hours after I cleaned the variable cap,again. fyi the last few years the previous owner keep the 1980 in his shop where his latest enterprise is compressing cedar sawdust into fire logs. Well needless to say the unit had quite the build up of cedar sawdust that unlike dust adhered to every surface it comes in contact with.
    So tomorrow we'll see where we are at.
    I can't remember the unit, a Sansui tuner, I think, that had the same Quartz lock feature. As I recall it was just a simple adjustment to tweak the Quartz sensitivity.
     
  18. kevzep

    kevzep Its all about the Music Subscriber

    Oh, no I would recap the tuner, I have never found an issue with alignment doing that.

    Very different from Sansui, there is nothing even remotely similar between any Sansui I can think of and the 1980 tuner, the 1980 is absolute TOTL in design and performance, really, if you don't have the gear or the experience I'd leave it.
    But of course we can't stop you tinkering, so if you want help, I can try.

    Could be that with all that dust, its gotten a good hold in the Bread slicer (Air capacitor) and it may take some deep cleaning to get it back, that will severely affect the sensitivity of the tuner....Hopefully that is it..
     
  19. Fhamre

    Fhamre Super Member

    Well the cleaning has seemed to make the Quartz lock and tuner work quite well. Where I live there are only two nearby FM stations I listen to. What I noticed after the extreme cleaning is that the station near 88.5 indicates a very strong signal while the other station at around 100 that usually shows a strong signal is less than what I had been getting. Other than that it is working well.
    The fan connectors and attached wiring I used concerns me as I feel the wire is quite thin in this application and may not be adequate for the current draw.But I am no expert.
    I may recap the tuner and APC board yet.
     
  20. kevzep

    kevzep Its all about the Music Subscriber

    I used some Molex connectors, made the cables myself because I have a Molex crimp tool, so that was easy.
    Here's a pick of what mine ended up looking like, you can't really see the size of the cable, but gives you an idea, I considered the current when I built those.
    I also put a bigger value resistor in one of those supplies too, it was in one of the discussions with echowars, I cant remember which one, but it just drops the voltage a bit more before the transistor so it doesn't quite run so hot...

    Once you said the unit was caked in dust I knew there would be more cleaning to do to the Air Capacitor, you were probably losing a lot of sensitivity through all the crud in there...
    maybe wait a few days and give it another go.

    Recap the tuner, but leave the APC, seriously not worth going in there if you don't have to. The APC is a very sensitive circuit, which is why its shielded...

    I think you are onto it with the cleaning...
    IMG_4635.JPG
     

Share This Page