Suppression capacitors are magical devices. - Page 1
Forum section: electronics / general

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: August 10, 2017, 05:21:52 pm
content: I got an old, defective Fein multi purpose power screwdriver (ASs 636, older version from late 70s / early 80s) for very little money.It was spewing sparks and barking like a mad dogUsual suspect: The suppression capacitor must be blown (and the internals were full of wooden saw dust).However, apart from the cap all parts are in absolutely remarkable shape. There is virtually no wear on the metal gears, the collector looks like new, brushes are in very good shape.I cleaned up the housing, removed all dust and grime (lots), disassembled the switch, gave its internals a scrub with deoxide, replaced the old cap labeled "FF" N 100M/5 0,1uF 220VAC +85°C 67.9 with a Vishay X2 0,1uF 275V~ F1774-415-3264 MKT I had stocked from another repair and now the tool is working as if it was a brand new machine.I always forget about what an impressive job that simple part does in taming the angry electrons in an inductive circuit.Do you know that feeling of taking certain things for granted and not thinking much about it until that certain something fails on you?It never fails to amaze me

author: Brumby
author_rank: Unknown
timestamp: August 11, 2017, 12:41:12 am
content: For a delightfully simple implementation, the suppression cap does do a brilliant job.Plus, a simple fix is always a satisfying outcome - and aside from bad solder joints, you can't get much simpler than a suppression cap.What amazes me is the times you spend (comparative) ages digging out an obscure fault which has drawn upon your years of experience - only to get an off-handed "Oh, you've fixed it. Thanks." response .... but when you come across a simple one, you get a fanfare, the title "Magician" and a glowing recommendation to all and sundry.It's just not fair - but that's how it goes.

author: jh15
author_rank: Frequent Contributor
timestamp: August 11, 2017, 04:04:54 am
content: do you mean a suppression cap as one with a resistor built in?

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: August 11, 2017, 08:13:57 am
content: Quote from: jh15 on August 11, 2017, 04:04:54 amNah. Those are the fancy ones in newer tools. I am talking simple suppression cap as in stone-age simple

author: jh15
author_rank: Frequent Contributor
timestamp: August 12, 2017, 03:56:57 am
content: I had suppressor caps with a resistor built in in the 70's on the bell labs stuff. Back when auto dialers used magnetic tape and lots of motors.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: August 12, 2017, 09:29:33 am
content: OT: The manual quotes The "Gesetz über technische Arbeitsmittel" (translates to: law on technical work equipment) from June 24th 1968. This law has been regularly revised in 1968, ’69, ’70... as far as I could find, so 1968 might well be the birth year of my machine. Newer machines have a three-wire assembly installed with an arrangement of three capacitors in one package as a triangular configuration: One big one in parallel to the switch and two smaller ones connecting the motor shielding / metal parts to the big cap. That is for EMC I guess?Edit: XY-Capacitor seems to be the correct term.

author: SeanB
author_rank: Super Contributor
timestamp: August 12, 2017, 10:35:39 am
content: Just that the cost of those RC assemblies is many times the cost of just buying a regular Class X or Y capacitor and putting in a series resistor. Wanted 3 for a contactor, and looked at the price of them, then went and got 3 2kV rated polypropylene caps that would survive any abuse there ( rated for TV line output transformer tuning, so rated for around 10A at 2 kV anyway) and some 1W 10R flame proof resistors to put in series with them. That 3 phase contactor sees a lot of cycles, and I really wanted to keep it working as long as possible. Probably over 10 million cycles now on a standard Omron plug in relay, it is surviving quite well driving the 100W 3 phase motor it controls. relay is cheaper by a lot over an inverter, though i could get some good braking with the inverter and use a common DC bus with the other motors to recover the braking energy as well.