Pioneer SX-535 Rebuild Finished - Thanks All!

[riverty]

I purchased this Pioneer SX-535 from a local shop. With the exception of the broken face plate in the tuner window, the unit is in great shape inside and out. All original and in working order. So, I decided that this would be a great unit to rebuild.

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Power Supply: I replaced the main filter caps with new Nichicon LKG Gold Audio Grade caps at 6800uF @ 63V. A bit higher than the original 4700uF caps but that's all I could get and no harm done. I replaced the bleeder resistors with new 5 watt resistors. All electrolytic caps on the power supply board (AWR-065) were replaced with new long-life Nichicons or Panasonics, depending on what was available from Mouser. All diodes and resistors were checked and found in good working order. I did add a small heat sink to the 2SD234, mostly because I had one around and, why not?

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Control Board: I replaced all electrolytic caps with new, long-life Nichicons or Panasonics. I also replaced all the light-blue Sanyo caps with new Cornell Dubilier, DME Film caps. All pots and switches were cleaned with DeoxIT.

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Tuner: All 6 light-blue Sanyo caps were replaced with new Cornell Dubilier, DME Film caps.

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Phono Preamp: All electrolytic caps were replaced with long-life Nichicons or Panasonics. I also replaced all 4 original 2SC1312 transistors with better sounding Fairchild KSC1845FTA transistors. Resistors were checked and found to be fine.

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Power Amp: All electrolytic caps were replaced with long-life Nichicons or Panasonics. The troublesome 2SA726 transistors were replaced with new Fairchild KSA992FBU transistors. Resistors were checked and found to be fine. I also replaced the original bias pots with new Bournes 362-line pots and set the bias at exactly 15mV for both channels as per the service manual.

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Front Panel: I decided to replace all the incandescent lights with LED's. I used a bridge rectifier and dropping resistor to power the whole display. I added 10 blue LEDs to the tuner dial, an orange LED for the tuning indicator, and white LEDs behind both tuner meters. I then replaced the stereo indicator with a red LED and appropriate dropping resistor to suit.

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And finally, I gave the whole thing a good cleaning, inside and out. Everything works prefectly and sounds amazing!

There were several posts in a few different forums that I used to gather the best information about the unit, replacement parts, and things to check, and I can't thank them enough for their wisdom on this project. It definitely pays to take some time and research things before you order parts and start work. Hopefully, the information in this post, plus the pictures will help someone else wanting to do the same.

Cheers all...

 

[EastPoint]

Very nice. Are you going to fix the glass? Any local glass shop should be able to make a new one for $10-15.

 

[cuda440]

Good luck on the glass. I had a hell of a time finding someone who could provide replacement glass for a 737 for a good price (quotes of $100 and $200 for ONE). It wasn't the glass so much as the holes required for the tuning shaft and the two switches that poke through. I eventually found a shop that would do it for $50. I did get 4 pieces for that price (a surprise when I picked them up) since they had to stack a few together when drilling the holes so as to prevent "tear out". Even then I had to go back a second time since the holes we a bit off from the acrylic template I gave them, the two switches didn't line up (they need to be pretty much perfect to work correctly).

I don't recommend trying to drill the holes yourself, at least not the one for the switch (tuner shaft hole is much more forgiving). I tried two different kinds of glass cutting bits and got either badly chipped edges or cracks radiating out.

You can check with zebulon1 if he has the dry transfer for the switch label.

 

[Jimbob3416]

When you replaced the caps on the tuner board did you have to realign it? I just started on my SX-535 and have been doing a lot of reading. I'm afraid to mess with the tuner as I have very limited test equipment and don’t want detune it. What is your recommendations on recapping the 535. Thank You. Jim

 

[EngineerNate]

When you replaced the caps on the tuner board did you have to realign it? I just started on my SX-535 and have been doing a lot of reading. I'm afraid to mess with the tuner as I have very limited test equipment and don’t want detune it. What is your recommendations on recapping the 535. Thank You. Jim

When I started my first recap, I was told that a realignment was usually only necessary if you messed with the active components.

 

[ivandezande]

When you replaced the caps on the tuner board did you have to realign it? I just started on my SX-535 and have been doing a lot of reading. I'm afraid to mess with the tuner as I have very limited test equipment and don’t want detune it. What is your recommendations on recapping the 535. Thank You. Jim

The old caps have drifted, no? And the alignment was based off the original value of the caps.
It's already unaligned, put new caps in it, it sure can't hurt.
And like Nate said, most of the serious alignment is based on transistors, ceramics, etc.

 

[EngineerNate]

The old caps have drifted, no? And the alignment was based off the original value of the caps.
It's already unaligned, put new caps in it, it sure can't hurt.
And like Nate said, most of the serious alignment is based on transistors, ceramics, etc.

Yeah I forgot to mention that. If they've drifted it's already out and they hopefully didn't put electrolytic caps in the oscillators where value really matters. Back then even new electrolytic caps were usually specced at like -20%+50% or -20%+100% even. Most of the electrolytic caps in the tuner section will be signal coupling or local power filtering, neither of which is going to be super value critical.

 

[Jimbob3416]

Thank you for your comments. I'm sure you'll hear from me again as I start the recapping. I haven't even ordered the parts yet. Still making a list of what I need....

 

[Jimbob3416]

We'll parts for power supply & amp board are on order. Looking at the position of the boards, do you remove & un-solder all wires and take the board all the way out to work on it? Looks like that would be easier to solder but you will destroy all the wire wrap around terminals and have to solder them back on. I guess I need a little guidance on this.

 

[UncleBingo]

No. Do not remove the wires or the pins. Not necessary at all. The boards can be carefully lifted for access. Don't flex them back and forth much. The wire is solid-core and you don't want to break it.

 

[Jimbob3416]

The power supply board I had to unwrap 5 wires on the bottom so I could lift the board to get at the solder side. I hope that was ok....I don't know how I could work on that board without removing those wires to tilt it up vertical. Yes, I see what you mean...those solid wires would snap off without much movement.

And as I look closer, at the top of power supply board post terminals have be soldered. Must have been replaced or moved too much and broke them off. So I guess the bottom will match.

 

[Jimbob3416]

Riverty: Looks like you recapped the tuner. Did it effect the tuning? Did you have to re tune it? Still waiting to hear form someone who did this and the affects.

 

[larryderouin]

Jimbob3416
Replacing the Electrolytics on the 535 tuner won't affect the alignment. I've recapped all of my x3x series unit's tuners with no problems. See posts #4 thru #7. (I missed it too the 1st reading.). Seriously. Go ahead and replace the electrolytics on the Tuner board. For the caps that are Robin Egg Blue colored SANYO's, are less than 4.7uf, and there is room for a Film cap, use a WIMA MKS series 50V cap. If you don't want to use the WIMA's, go with Nichicon UKL Low Leakage (very quiet background) caps.

 

[Jimbob3416]

Yes, I have them on order. Thanks for giving me the push I needed to go ahead with the recap. I've been looking on line for a shop that would re align the tuner in case I messed it up. All are out of state. I don't know of any Hams with a MPX generator. What about the UKW caps? I have some left over with the recap on the other boards. What about transistors....can they be replaced without a re tune?