Sigurthr
0
- Joined
- Dec 11, 2011
- Messages
- 4,364
- Points
- 83
Hey all!
I finally reworked the mains power and grounding situation in my lab/office the other day, after three years of struggling with issues. The culprit came out to be that the circuit I'm on was illegally bridged with another circuit. Fixed that finally. The main problem I was having, other than lack of grounding so the ground line would float at ~90VAC, was that the mains and neutral lines were reversed at the junction box, and reversed at several outlets. So if you touched something on one outlet and something on another at once you'd get a nice 120V jolt.
I go to fire up my 3kW SSTC today after nearly a year hiatus and I hear that familiar yet unwelcome BZZZRR from my variac. I didn't even hit 100W before it started. Powered down, pulled the variac apart to find that the internals are wired wrong and it uses undersized wiring. Cheap Chinese piece of junk. It had the hot and neutral reversed inside, the power switch switched only the output line, not the input mains, and the autotransformer itself was wired wrong so that there was 120V between ground and spindle at all times. Rewired it up to code.
While rewiring the variac one of my two dual 48" fluorescent lamp fixture began to pulse on and off, and a few seconds later that unmistakable acrid stench of baked electrolytic capacitor filled my room, with accompanying smoke. Took it down, ripped it apart to find both cheap 200V 47uF electrolytics had failed, one catastrophically. I didn't have any caps that size (physically) which had a useable voltage rating, so I improvised...
Blown caps on circuit:
Blown caps desoldered:
My fix. 2x 125uF 500V electrolytic caps circa 1966.
May not be pretty, but those caps are working just fine. Hopefully the gremlins have moved on to someone else's house now.
I finally reworked the mains power and grounding situation in my lab/office the other day, after three years of struggling with issues. The culprit came out to be that the circuit I'm on was illegally bridged with another circuit. Fixed that finally. The main problem I was having, other than lack of grounding so the ground line would float at ~90VAC, was that the mains and neutral lines were reversed at the junction box, and reversed at several outlets. So if you touched something on one outlet and something on another at once you'd get a nice 120V jolt.
I go to fire up my 3kW SSTC today after nearly a year hiatus and I hear that familiar yet unwelcome BZZZRR from my variac. I didn't even hit 100W before it started. Powered down, pulled the variac apart to find that the internals are wired wrong and it uses undersized wiring. Cheap Chinese piece of junk. It had the hot and neutral reversed inside, the power switch switched only the output line, not the input mains, and the autotransformer itself was wired wrong so that there was 120V between ground and spindle at all times. Rewired it up to code.
While rewiring the variac one of my two dual 48" fluorescent lamp fixture began to pulse on and off, and a few seconds later that unmistakable acrid stench of baked electrolytic capacitor filled my room, with accompanying smoke. Took it down, ripped it apart to find both cheap 200V 47uF electrolytics had failed, one catastrophically. I didn't have any caps that size (physically) which had a useable voltage rating, so I improvised...
Blown caps on circuit:
Blown caps desoldered:
My fix. 2x 125uF 500V electrolytic caps circa 1966.
May not be pretty, but those caps are working just fine. Hopefully the gremlins have moved on to someone else's house now.
