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Okay, I've been trying to figure out what this cap is (I got a pile of them as surplus). I was told they're a film cap of some sort, though whether mylar or polypropylene I can't be sure. The entire marking is thus:
PH 822H 1250VHOV
I can't make heads or tails of the "PH" of "HOV" ("high over-voltage"? I dunno . . . may be "H0V") designations, as they don't fit with any references I've found. I'm assuming "PH" is a dielectric code, but . . . eh. Anyone have an idea? I mean, I could always wire them up and see how long they last, but I'd rather save them for what they're suited for if they're not going to take the beating from a TC.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I'd say it's 8200 pF (8.2nF, code 822=8,2, and 2 zeroes in pF) 1250 Volts no idea what HOV means
I think it's a multi-layer ceramic capacitor with a very high "K" dielectric which means high capacity per volume but very lossy at high frequencies.
ok for dc and low-frequency use ... e.g. cockroft-walton voltage multiplier not very good for Tesla Coils etc. ... they will overheat quickly and give poor performance.
You sure? I've not seen +/-3% multilayer ceramics. I'm fairly sure they're (as sold) a film cap of some sort. However, if they are just mylar, they're relegated to a CW regardless . . . (Large ceramics usually have standard dielectric codes printed on them anyway.)
Obviously, for my purposes, I'm hoping it is MKP! *grin* Given that the dielectric code is either a mystery ("PH"), or not listed (if "PH" refers to something else), is there anything in the way of a test I could run, short of putting them in the MMC and using it until it overheats/blows? I don't have my TC out here . . . I've recently moved across the country, so I'm putting together a new one (of course!): so I have no way to stress-test them in a working coil at present.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
well, I've pulled a cap that looks awfully similar to yours from an old TV.. It was used as a snubber for the HOT, where it sees 15kHz at 1500Vp-p, so I guess it should be quite a quality cap
Well, according to my handy-dandy pica-stick with decimal inches (Yay for art supply stores! I'll bet they never thought it'd get used for HV electronics!), it's an inch wide, just about 0.6" tall, and around a quarter inch thick at the center.
I am going to hacksaw one . . . (note to self: buy new hacksaw blades) . . . however, I've never compared MKP to MKT in section . . . do they identifiably different?
I think I'll set them aside for an MMC anyway . . . the worst that can happen is they'd overhead, and I'm just feeding this with an OBIT I picked up from an estate sale, so I can't have too terribly long of runtimes anyway.
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Cap ID - Dielectric code?
