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Creepy switch activity

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8/22/2000 3:29 PM

Creepy switch activity

Warning - Sad story of dorkitude & failure:
Built a Minibooster, boxed it found it distorted at low volumes. Tore it apart bit by bit - replaced everything on the pcb. Gave up - built LPB instead put it in same box, different pot, same switch & Mil. bypass. Distorts - Particularly at low volume. Lots of aggravation.
The switch is a Carling but has always acted funky, sometimes not switching and going silent if hit too softly.

Can the switch be the source of this distortion (kinda a ratty diode-like rasp on sharply hit chords)? Could a slight intermittant condition be causing the uglies here? I find the "on" lugs to have about 1 Ohm on my meter and the "off" ones to show OL. or 1 meg./1.5 meg or over depending. A known good switch shows 1 ohm and OL. respectively but is not in a circuit.

What think y'all? Do these readings make any sense at all? I am now nuts.

Thanks,
- A

8/22/2000 6:27 PM

Any switch is rated at a certain number of switching actions for its lifespan. Most of us probably don't reach that maximum before we get bored (although in my older son's cases, absentminded click-click-clicking has probably led me to overestimate the remaining lifespan of my switches; it's like bloody bubble-packaging, I tell you) with the effect.

Take one apart, and you'll be amazed they ever work at all. After all, YOU are pushing down, and the switch is going *sideways*. How wierd is that, eh? Sometimes, if the switch housing permits, you CAN take one apart, "rehabilitate" it by re-tensioning or cleaning, and put it back together. Not always, but sometimes.

Do consider heat related transistor damage as a possibility, though.

8/22/2000 7:33 PM

Thanks Mark - The trans. were the first thing i shotgunned. The second circuit i built was Thouroughly heat sinked while soldering.
I also know what you mean about the switches it is a wonder they ever work- this paricular unit has a new switch - I was kinda hoping it had yet to "Break In".
I think the first person who works out the tiny low parts momentary/electronic audio switch gets a big giant cookie here in DIY land. I think switches have been both my biggest headache AND biggest cost.
POOP!

Who's got the coole soft switch!?

8/23/2000 6:19 AM
Pete	Adrian, There's been a lot of talk lately on Arons forum about the carlings reliabilty lately. Maybe this could acount for it? However, does the effect do it even without the switch connected. I'd try that scenerio first Pete

8/23/2000 1:29 PM
paul perry	That's a good idea Pete, it wouldn't take long to just hard wire the unit with the switch replaced by wires in one position, then the other. "When the wiring gets weird, the weird get wiring."

8/23/2000 3:18 PM

I did try that with jumpering but not usoldering the leads - it is kind of a toss up really - usolder the switch lugs and possibly wreck the switch (of course it is funky anyway) or the pcb side.
It still makes an ugly sort of crackle on hard chords when jumpered but i really should unsolder/resolder. I'll do that this evening.
I even shotgunned the tran on my second pcb to no avail. BTW EH LPB Clone Voltages C - 6v
B - .7v
E - 160 mv
These seem about right? I'll break out my "Art of Electronics for some clues.

Thanks Again gents!

8/24/2000 1:45 AM
Pete	Adrian, drom the measurements you gave it looks like it should work, although I admit I haven't checked out the circuit yet. Best off and remove the switch for now until you get the board working properly first. Fix one problem at a time! Pete

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