SX-3500 repair and restoration

[nicholas2381]

Back to Pioneer for this project. I present to you a mostly-functioning, decent cosmetic Pioneer SX-3500 from my project pile:



Primary issues on first inspection:

Switches for speaker A, speaker B, tape monitor and loudness won’t stay engaged.

Slight volume imbalance (left channel slightly louder than the right).

Positive speaker terminal for left speaker of A has lost its springiness.

Needs a good cleaning, but otherwise in decent shape. No obvious burned or exploded components.

 

[onwardjames]

I had a little SX3400. Sweet, tiny little unit. I sold it to some fella.

Good luck with this sweet little guy.

 

[nicholas2381]

Thanks!

 

[RICK KING]

Hi @nicholas2381

Let us know what you do to remedy, especially speaker imbalance. I like my SX-626 as a tuner/preamp for my SA-9500. Seems to work real well,

Cheers!
Rick

 

[fromnowon]

Switches for speaker A, speaker B, tape monitor and loudness won’t stay engaged.

that seems like the first issue to tackle . . .
Does D5 help, or not?

 

[nicholas2381]

Hi @nicholas2381

Let us know what you do to remedy, especially speaker imbalance. I like my SX-626 as a tuner/preamp for my SA-9500. Seems to work real well,

Cheers!
Rick

Will do! I’ll be documenting the entire process in this thread.

 

[nicholas2381]

that seems like the first issue to tackle . . .
Does D5 help, or not?

Agreed - that’s step 1.

Unfortunately it’s a known mechanical failure with the switches on these units. The small plastic latch breaks and thus the it won’t stay engaged. 1:1 replacements are unavailable, so I’ll need to find some close matches and do a little engineering to make them work. Other AKers have done similar things to good success.

 

[nicholas2381]

Hi @nicholas2381

Let us know what you do to remedy, especially speaker imbalance. I like my SX-626 as a tuner/preamp for my SA-9500. Seems to work real well,

Cheers!
Rick

There’s also a chance that the imbalance is actually just the meter needing adjusted. It didn’t sound like it, but I’ll verify with the oscilloscope soon.

 

[fromnowon]

I'd try it with headphones, if it's good on the DBT, just to see how it sounds for awhile.
Maybe you could temporarily jump a speaker switch to move ahead . . . that might be a crazy idea?

 

[nicholas2381]

Doesn’t seem like a crazy idea.

 

[fromnowon]

It looks like the speaker switches 12-pin, so we have to find some of those . . .
I guess SP A is "on" and SP B is "off" . . . ?

 

[nicholas2381]

I ordered a variety of push button switches from West Florida components that should do the trick (done by the other AKer):

https://www.westfloridacomponents.c...zontal+Latching+Switch+1A+28V+CIT+DL4LCQ.html

https://www.westfloridacomponents.com/SW015PD/Push+Button+Switch+Multipole+4PDT.html

Also ordered a handful of all the 6 pin options. Good to have stock on hand.

 

[fromnowon]

Cool
4 pole double throw . . . that makes sense.
I'm selfishly using your thread to learn about switches.

 

[nicholas2381]

Learn away! I’ll be sure and share which ones work. That’s why I document all my stuff in threads - to share any knowledge gained for others.

 

[nicholas2381]

Appears the SX-3500 only has a couple shoot-on-sight transistors: 2SA726 and 2SA798, both of which are replaceable with KSA992 (2 x config for 798). I should have plenty of those on hand.

 

[nicholas2381]

I pulled together a cap list for a complete recap of all the electrolytics. Subbed in film caps for all caps 10uf and below. I also upped the voltage rating for each replacement to give everything a little more head room. I'm attaching here for anyone who wants to review or use in the future.

 

[merlynski]

 

[Schanz]

I have a 3700 on loan to my daughter. That will be a restoration someday. Probably not too dissimilar.

 

[nicholas2381]

Initial measurements coming soon - just have to find time to get to the bench.

 

[nicholas2381]

Know what’s better than unlabeled PCB components? Labeled PCB components.