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AGH! Why do things keep breaking on me?!

Ah. There's your problem. Three threads. Bad flux. Oh boy.

Still, provided your analog meter isn't borked you can still get those readings. After you got the bad stuff off. Or maybe now it's the time to enlist the help of someone more at home with electronics.
 
PE9ZZ said:
Ah. There's your problem. Three threads. Bad flux. Oh boy.

Still, provided your analog meter isn't borked you can still get those readings. After you got the bad stuff off. Or maybe now it's the time to enlist the help of someone more at home with electronics.
Click to expand...


I guess it's quite borked. The meter doesn't work for anything except impendance readings, which I'm sure aren't accurate. I even tried to measure the voltage of a brand new AA battery, and I couldn't get a reading.
 
PE9ZZ said:
Ah, bummer...
Click to expand...

Here's a list of all the things I've tried so far:

1. I've checked the fuses. There's only 2 fuse holders in the power supply section of the board, and one of them is empty. This was intentional from the factory, I don't know why, though. I tested the single fuse's resistance with my multimeter, and it made the multimeter spike, so I guess that means the fuse is good. Looks to be in good shape as well.

2. I've done a survey of the board and inspected the surface for any burnt diodes, capacitors, and resistors. Nothing. Everything looks perfect.

3. The receiver worked perfectly fine before this recap job, absolutely no issues. I made sure I did a clean and thorough job replacing the two filter caps, and cleaned up all the excess flux I could. But the receiver kicked into protection mode after power on. Replacing the filter caps with the old one did not fix the issue. And I'm 100% CERTAIN that I did not mess up the polarity. There are markings on the board, and I also took pictures of the capacitors before replacement. This leads me to believe that some flux residue could be to blame here.

Any ideas on what else I can do? I'm going to take voltage readings of the caps and other components. I just have to figure out my way around this multimeter, first.
 
petehall347 said:
set your meter on ohms and put probes into some flux to see how conductive it is . obviously clean the probes afterwards .
Click to expand...

Just tried that, and nothing happened. When set to ohms mode, the meter spike bounces up and down, but it didn't do anything in the flux.
 
petehall347 said:
set your meter on ohms and put probes into some flux to see how conductive it is . obviously clean the probes afterwards .
Click to expand...

This is probably a really dumb question, but is the receiver supposed to be turned on while I take the readings with the multimeter?
 
I FIXED IT!!!!

This was the most simple fix ever.

All I had to do was put the bottom service panel back in.

20200804_133435.jpg 20200804_133439.jpg


See that depressed screw hole? I noticed that there was a metal plate on the PCB for where that screw is supposed to go. This made me realize that this service panel is acting as a ground for one of the PCB components. As soon as I screwed the panel back in, the receiver fired right up without any issue! Man, oh man. I was getting really worried...
 
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Now, I'm going to solder the new filter caps back in. I promise that I won't screw anything up this time. ;)
 

Perfectly fine as in the receiver worked. These filter caps are long past their prime. They don't do a proper job at filtering out noise anymore, and they would squeal quietly when I turned off the receiver.

And by filtering out noise, I mean outside noise. Turning on my ceiling fan would cause a loud pop to be heard through the speakers.
 
Binkman said:
edited:
missed last post....
So??? what led you to putting the cover back on? :D
Click to expand...

I realised that there was a little metal plate on the PCB, where that screw is supposed to hold in the service panel. It made me think, huh, isn't this a grounding point? And then it all clicked!
 
Sorry you read my unedited post.
Yes... that explains it. oft these ground pcb traces are missed and or need tightening, too.
 
petehall347 said:
so are both units working now ?
Click to expand...

Technically, the cracked SX-50 could be working, now that I know what the problem was. But it's a scattered mess of parts right now. I'll be putting it back together eventually. I've done enough stereo repair for now, heh.
 
These new filter caps did make a difference as well. I currently have the stereo tuned into an FM station, playing through headphones. The bass has increased noticeably, and I no longer need to have the bass maxed out. There's also no more popping noises when turning on my ceiling fan. I can't say how it sounds when hooked up to speakers, because I turned the bias potentiometers all the way counter-clockwise. I'll need to pick up a DMM and make the proper adjustment before hooking it up to my speakers.
 
Does anyone have any advice or tips on how I can safely adjust the bias? This is what my service manual says:

20200804_142821.jpg
 
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