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Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Alright, I got one working like a charm, but the second one only works when the variac is turned past 70% or so, I'm pretty sure it's the variac, since outside of that (once it's turned past that spot) it works perfectly, and it definitely has power, it's not a slow climb to normal, it's either good or bad.
I cleaned the variac with an eraser, didn't seem to make much difference, looking at the contacts it looks like the silver coating has been worn off and it's down to the copper wire, and the brush (not sure exactly what it's called) is pressed against it fairly loosely.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
Well you can test the variac easily enough, just monitor the AC voltage out of it. It's a simple enough device, so troubleshooting should not be too difficult. My guess is the loose brush is the problem. Given the wear on the track (which should not be a problem) my guess is the brush is simply worn out. If you can find a similarly sized carbon brush from a motor or something you can probably file it down to fit.
Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Righty, theres the loose brush which I'll replace, and theres also a second inner slider track that gets the power to the output line, and it looks pretty darn dirty and slightly bent, so I'll look at that too. Both require disassembly... woot
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Not sure if you've solved the rectifier problem yet, but old 12V motorbikes, etc often have these (12 V, reasonably high amperage).
Some are the type with plates for cooling, others are potted, with a metal plate in the back which usually bolts to some form of heatsink (often just a metal surface on the frame, or something). Your local japanese bike breakers should be able to help here if you don't want to 'splash out' for a new one.
EDIT: 12V barrery chargers also have them, but they tend to be lower amperage. (depends on rating of charger)
Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Right, got it fixed, I disassembled the variac and cleaned all the contacts (primarily a wavy copper ring that was really dirty) using sandpaper, an eraser, and acetone. Now it works lke a charm
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Check out my new PSU! (fixed variac)
