Pioneer SX-737 Restoration

Discussion in 'Pioneer Audio' started by StraightCase, Dec 28, 2018.

  1. StraightCase

    StraightCase New Member

    Messages:
    10
    Location:
    Central Ohio
    I have decided I am going to take on the restoration of my recently acquired Pioneer SX-737. This unit does not appear to have seen much use at all and I even have the original packing and box. Almost like it came out of a time capsule. :jump:

    Pictures: https://imgur.com/a/2yCpNWV

    The unit is sounding great, but I really want to get these old electrolytic caps out and replace with new to avoid trouble.

    Electronics are not new to me and I do have experience working with electricity on both standard household and industrial 3 phase circuits, but nothing quite like this. I do have some pretty decent tools for the job. Hakko 936, MG Chemicals 60/40, SRA Rosin Paste Flux, solder sucker, braid, 170 cutters, Pomona mini-grabbers for the multi-meter, surgeon's hands (welder joke) :blah:, etc. So I am off to a pretty decent start, but by no means an electrician or double E.

    So here are my questions. I have gone through many older threads on this very topic and have made a BOM (largely from Mark the Fixer's) for the components I will use in this preventative service and there are a few components that I am not going to be able to source. Any changes I am making to Mark the Fixer's BOM are marked in yellow waiting for approval from more qualified people than I; additionally there are some that are marked in red that I simply am lost on what would be a good substitute. Most of them are those film caps found on the tuner board and others. Also, mouser is out of 512-KSA1220AYS should I just wait til they arrive? I will be installing 863-1N4004RLG as my unit does not appear to have it between pins 9 and 10 on protection board banded side to 10, right?

    Is it normal to hear some crosstalk (terminology?) or bleed from the FM radio on the recording functions?

    Any recommendations on replacement main filter caps? My original caps are ELNA CE-W 50v 6800μF 85C capacitors. I am still searching for an appropriate replacement for those.

    Lastly, should really replace all these transistors? Not that it is a big deal, but do they really need it? Do they degrade like electrolytic capacitors do over time, or is it with use?

    What say ye?
     

    Attached Files:

    Last edited: Dec 28, 2018

     

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  2. Motnick

    Motnick AK Subscriber Subscriber

    Messages:
    384
    Location:
    Wyandotte Michigan
    A very good unit to start with. You will be very happy with this 737 once it’s been gone through. Many of the transistors in this unit are known to fail and should be replaced. These should all be listed in the BOM lists you’ve found.

    I don’t see a dim bulb tester listed in your post. Be sure to build one for yourself before you proceed. I was given the same advice when I was starting with my first unit, also a 737. The DBT is an essential tool which I have used on every unit that I have worked on. Only costs a few bucks to build.
     
  3. StraightCase

    StraightCase New Member

    Messages:
    10
    Location:
    Central Ohio
    That is the first thing I did. Thank you for the reminder! I am not taking any chances.
     
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  4. StraightCase

    StraightCase New Member

    Messages:
    10
    Location:
    Central Ohio
    As far as replacing the ELNA CE-W 50v 6800μF 85C main filter caps goes I have been doing some looking.

    If I wanted to stay at 6800μF it seems that either of these two may be a good choice:
    Vishay 256 PMG-SI: 594-MAL225631682E3
    Cornell Dubilier 381LX: 5985-85B-80V6800

    Digging deeper into the forum I have turned up this Nichicon UVZ at 10,000 uF being used: 647-UVZ1H103MRD

    But what about theses other 10,000 uF caps?
    Nichicon LGU: 647-LGU1H103MELB
    United Chemi-Con KMH: 661-EKMH630VSN103MA5
    Cornell Dubilier SLP: 598-SLP103M063H9P3
    EPCOS / TDK B41252: 871-B41252A8109M000
    EPCOS / TDK B41252: 871-B41252A6109M000
    Wurth Electronics WCAP-AIG5: 710-861020786030
    Wurth Electronics WCAP-AI35: 710-861140786024

    What is up with those last two Wurth leakage currents? According to mouser 12600 uA vs 2381.18 uA. That seems pretty significant! Which makes me wonder, is higher or lower leakage current better for this application?

    Will there be any harm, undue stress, or other ill iffects changing from 6800μF @ 50v to 10,000μF @ 63v?

    Sorry for all these questions. Trying to learn and think everything through as much as I can to avoid unnecessary trouble with this SX-737.
     
    Last edited: Dec 30, 2018
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  5. StraightCase

    StraightCase New Member

    Messages:
    10
    Location:
    Central Ohio
    First round of caps have come in, more on the way. Going to order the transistors too. I still need some help figuring out the few caps that I cannot source so I can make this a one timer. Don't want to have to take apart and reassemble any more than I have to. Should be a fun project and a great way to spend some time after my hernia surgery next week. Hahaha!
     
  6. markthefixer

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

    Messages:
    21,148
    Location:
    Bensenville,Illinois
    First I don't want to reward private solicitations for help. NO private help, Public help is freely given WHEN I can find time to do it.

    This has been covered in the past, and plenty of the guys should remember.

    caps were -20% to +80% back then, so 180% x 6800 = 12,240

    going higher in capacitance MIGHT be helped by new stronger rectifier diodes between the caps and the power line to handle the increased surge.
    The e-core transformer DOES set an upper limit when saturated, unlike toroids which will surge huge amounts of power.Which is WHY the Pioneer models with Toroid transformers have power-on surge control circuits.

    Leakage is related to other things such as heating, more significant in the electromagnetic hell of a switch mode power supply. As the big caps get more expensive, they meet stricter and stricter specification relevant to these high performance power supplies.

    Other obsolete caps (not the huge main caps) have had currently available subs found.
     
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  7. StraightCase

    StraightCase New Member

    Messages:
    10
    Location:
    Central Ohio
    Thanks for the help markthefixer! I will take a look at possibly replacing that rectifier.

    Wound up going with the Cornell Dubilier SLP 598-SLP103M063H9P3 for the main filter cap replacement.

    Did a lot more digging and turned up additional results. Updated BOM has been posted. Pretty confident in this one, but if anybody sees anything strange let me know!
     

    Attached Files:

  8. pauls1

    pauls1 Active Member

    Messages:
    133
    Location:
    Essex, UK
    I'm sure that you know this already & it is something that you won't need just yet......but here it is....

    note: the DC neutral voltage and idle current procedure in the service manual incorrectly identifies adjusting VR1 (pin 3 voltage to ground) and VR2 (pin 17 voltage to ground) for 0v and VR3 (voltage between pins 2 & 1) and VR4 (voltage between pins 18 & 19) for 20 millivolts. It correctly identifies the VR1, VR2, VR3 & VR4 positions in the drawing.

    the CORRECT DC neutral voltage and idle current procedure is to adjust VR3 (pin 3 voltage to ground) and VR4 (pin 17 voltage to ground) for 0v and VR1 (voltage between pins 2 & 1) and VR2 (voltage between pins 18 & 19) for 20 millivolts.
     
  9. StraightCase

    StraightCase New Member

    Messages:
    10
    Location:
    Central Ohio
    Thanks for that! I found that out a couple days ago after trying to adjust it per the manual. Noticed they were switched around and found a thread with an updated page which I printed.

    Little off topic, but got the hernia surgery. Feels like a perpetual nut shot. Hahaha. Probably going to get started on this pioneer sometime next week depending on how I feel. Will post pics when I do.
     

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