Power Switch Starting to Arc

[djwhy60]

I have my beloved STA-78 as my main system in the man-cave. Noticed the other day that the power switch is starting the dreaded arc. I do not want this piece of joy to die! I can do minor surgery....very mechanically inclined...but worry it may be one of those unobtainable pieces should it decide to crap out. Any advice ahead of time???

 

[mbz]

The snubber(?) capacitor C804 across the power switch is designed to suppress the spark, maybe it's on the way out/failed.
Suggest you replace it, 0.01uf, 600, 800V polyproplyene.

 

[djwhy60]

Thank you very much

 

[merlynski]

Here is an easy modification that can resolve the issue of fried power switches, takes 2 components, a bit of wire and a little soldering:
http://audiokarma.org/forums/index....orth-5-and-an-hour-or-so-of-your-time.504673/

 

[djwhy60]

Here is an easy modification that can resolve the issue of fried power switches, takes 2 components, a bit of wire and a little soldering:
http://audiokarma.org/forums/index....orth-5-and-an-hour-or-so-of-your-time.504673/

Thank you very much....have to do my homework on it...but seems pretty easy!

 

[Raccoon1400]

I've done the triac mod a couple times, I'd highly recommend it. If the switch has only just started arcing that makes it a lot easier.

 

[markn2wae]

If the power switch is on a rotary control with other functions (speaker selector for example) and is of the what I call the "match box" style of housing that is placed over the rotary shaft and supported at two ends on threaded rods, it can be removed and refurbished (it MAY even have a set of UN-USED contacts on it!

Yes, removing it, re-tensioning the contacts and cleaning them (a relay burnishing tool is needed) is a fair amount of work but I mention it here as another option in addition the the (good) options mentioned above.

Mark T.

 

[merlynski]

If the power switch is on a rotary control with other functions (speaker selector for example) and is of the what I call the "match box" style of housing that is placed over the rotary shaft and supported at two ends on threaded rods, it can be removed and refurbished (it MAY even have a set of UN-USED contacts on it!

Yes, removing it, re-tensioning the contacts and cleaning them (a relay burnishing tool is needed) is a fair amount of work but I mention it here as another option in addition the the (good) options mentioned above.

Mark T.

Indeed, but If you do all that, do the triac mod also and you will never need to disassemble it again. Plus those rotary switches are a bear to find if you have to replace it.

 

[markn2wae]

Good idea!, but I never seem to "plan ahead" and have the triacs on hand!

Mark T.

 

[Alan0354]

Use an inrush current limiter in series of the AC line, then have a 1W 10ohm resistor in series with a 0.1uF film cap ( 400V minimum) across the two terminal of the power switch to suppress the arc.

If you have the patience, this is my thread on this as I burned a new switch in 3 days time!!!http://audiokarma.org/forums/index.php?threads/how-to-protect-the-power-switch.772569/

I am too lazy to go for the fancy fix, after I put in the inrush limiter and arc suppressor, it's been over 3months and still working like a champ. Hopefully it will last forever.