• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer sx-2000 mode switch

James Cox

James Cox

AK Subscriber
Subscriber
Hey I'm currently restoring a pioneer sx-2000 tube receiver for a friend and I've ran into a small problem. The mode selector switch is broken and also missing the knob. Not having much luck finding a replacement. Anyone know where I can find one of these and possibly a knob? The switch goes Stereo-mono left- mono right.
PXL_20220608_172912160.jpg PXL_20220608_172916444.jpg
 
Register to hide this ad
I was thinking the same but these old.pioneer tube units are nearly impossible to find. Not sure what term to search to find this part on eBay or whatever
 
The switch looks OK - though it likely needs cleaning. The shaft could be built up with epoxy and metal tubing, or a knob could have an insert added to fit the broken shaft. Or a shaft could be swapped from a different switch if a compatible switch can't be found. Sorry to say I scrapped one many years ago without saving such parts...though I may have some knobs.
 
True, the switch does work without issue. The knobs missing so I'd have to track one down. I like the idea of adding a metal insert to the knob once I find one tho
 
if you can make one out of an SX-990 work, I have one of those as a parts hulk. Those have rev/stereo/left/right/L+R for positions. Could probably modify the stops to reduce them but I don't know how different it might be otherwise.

I do have something unrelated with a broken split shaft like this. The "fix" was to hold the broken piece in place, put some paper in the gap, and stick the knob on. Holds the knob fine, and the control works. Its not a click switch, just a level control, so it doesn't ever see much load.
 
I think I'm going to try a metal insert in the knob to keep it in place. I'll post pics once I get it goin!
 
Well finally finished replacing most of the caps and while the unit sounds great there is smoke coming from the power transformer and it's getting incredibly hot. Double checked my work and everything looks good so I guess I'm looking for a replacement transformer now. The part no. On this one is at-5253a. Is there a drop in replacement available or will I have to send this one off to be rewound? Never replaced a transformer before so not sure what to get since I can't find an original.
 
How much current is it pulling?
Compare that to expected power. Something else may be causing excessive power draw.
 
Well a clamp on meter over a single conductor will measure amps. Otherwise a multimeter must be in series with the power line- all current flowing through it- to measure it. As this is not very convenient and often exposes 120v sometimes people use plug in devices like kill-a-watts or similar things. I didn’t really know what you have available or feel comfortable with.
 
Im comfortable taking live measurements. I'll see what it's showing when I get to the shop in a few hours and report back. If it is the power transformer causing the issue how do I determine a safe replacement? I could post the schematic if that helps but can't find any specs for the power transformer online
 
If its drawing a lot, pull the tubes and see what it draws with no tubes installed. Should be very little if the transformer is good, any significant amount of draw with no tubes indicates a problem.

schematic would go a long way, we can probably work out the current demands from that. The physical mounting you'll have to measure and figure out.
 
Right on, I tested it with the tubes pulled and the bridge rectifier disconnected yesterday and the transformer still smoked after a few minutes idling. I'll take some measurements when I get in and post back. Here's a copy of the schematic. It won't let me post the PDF so all I have is a screenshot. I can post a link to the site I got the schematic from if needed though. Thanks!
 
yeah if its smoking with nothing connected, that pretty much puts the nail in the coffin. That sucks.


link would help a lot, that resizes so small I can't read it.
 
Alright so with a little help from another AK member I have installed a replacement power transformer. No more smoke and the amp sounds great in aux mode but now there's no left channel on the phono side. I tested with 2 turntables, both worked on my other system so it has to be something wrong with the pioneer.
Switching from stereo phono to mono phono makes no difference, still no left channel. The schematic I have is pretty busy and since I don't have much experience with schematics I'm having trouble figuring out what parts correspond to the phono section. Any suggestions?
 
You must log in or register to reply here.
Back
Top Bottom