SX 750 Power Switch

GreyOwl

Active Member
Going to be replacing a couple of filter caps in my SX 750 this weekend to get rid of the hum that has been there since I got it a couple of years ago. Was also going to tear into the power switch to clean it and get rid of the flickering and hesitation when turned on, but my switch seems different than the ones previously shown on AK as it is not a square assembly like in all the repair pictures but a round switch about the size of a quarter and 1/2" thick(Pic below). I would imagine the guts are similar but wanted to check here before I dig into this. It looks to unscrew off the back of the selector to get into it just like the square one.

SX750PowerSwitch.jpg


Here is a pic of the caps I am going to replace. They look a little overheated to me. After they get replaced I am going to run a chec on all the voltages MTF has recommended in other threads.

SX750Caps.jpg


Charles
 
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Great! Thanks for that link. My searches only brought up the posts with the square style switch, so never saw those. At least I have an idea of what I need to do before I get in to it now. Is there a possibility of a different value arc suppression cap that would work better to prevent this?
I have been also thinking about using a relay. You didn't have a manufacturer or part number of the one you used in your post so if you have the info could you post it here?

Charles
 
Tyco/P&B Relay, T92P11A22-120 (30A DPDT 120V )

Honestly, it was complete Cold War style overkill to the megaton degree - 60A switching after the AWG 16 zip cord is just a bit overdone, but it won't ever be the weak link. But it fit, and was under twelve bucks.
 
Will look to getting that relay or something very similar, especially after today. Didn't get anything done over the weekend but got into it this morning. Started with the two caps which went very smoothly.
After every phase I plugged it in and used the headphones to be sure nothing bad happened.
The two caps cured the hum problem so started the disassembly of the power switch--nope can't do that without doing several more things before I can even get close to it. Finally got it apart and it looks really bad inside so I scraped and cleaned the best I could at the time and put everything back together. I will add the relay at a later date. Checked everything with the headphones before buttoning it back together and it sounded great still with no hum.
Put it back into the system and fired it up --bummer -- no right speaker. Still works great with the headphones so will do a bit of troubleshooting again tomorrow, like swapping speaker leads and such. I suppose I may have pulled a wire loose on the speaker portion of the switch. I couldn't believe how much I had to unwind wires and parts just to get the switch out of the chassis.

Charles
 
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