carey@uiucdcs.CS.UIUC.EDU (03/05/86)
Two things:
1) I think this has been discussed on the net before, but I didn't
follow it at the time--is there any way to test whether a MOV
is still in working condition? I have a power strip that
has three MOV's the number on them is:
MDC
Z131
20ULB
I don't have a data sheet on them. Is there any particular importance
to their placement on a strip? This strip is laid out like this --
(looking from underneath)
(hot) /- - /- /- - -
/ MOV /
(ground) .47uf400V - / - \ - MOV - - -
\ MOV \
(neutral) \- \- - \- - -
Anyway, I think the strip might have had lightning go through it. Besides
just replacing them, is there any way to TEST whether they are still good.
While we are at it, in what cases are MOV's effective--small power surges,
voltage variations caused by large motors, lightning strikes, induced voltage
from lightning, static charges.
2) Does anybody know a good source for tubes for VT125 terminals. Good means
cheap, and a reasonable (4 - 8 weeks) delivery time. In general, what are
good sources for CRT's? Has anyone tried to use "rebuilt" tubes? How good
are they and how long do they last?
-John Carey
-- {ihnp4,convex,pur-ee}!uiucdcs!carey carey%uiuc@csnet-relay.arpa
carey@uiucdcs.CS.UIUC.EDUlarry@kitty.UUCP (Larry Lippman) (03/12/86)
In article <11600005@uiucdcs>, carey@uiucdcs.CS.UIUC.EDU writes: > 1) I think this has been discussed on the net before, but I didn't > follow it at the time--is there any way to test whether a MOV > is still in working condition? I have a power strip that > has three MOV's the number on them is: > ... > Anyway, I think the strip might have had lightning go through it. Besides > just replacing them, is there any way to TEST whether they are still good. The only effective way to test a MOV is by using a semiconductor curve tracer. We have a Tektronix curve tracer with external high current adapter which will simulate the overvoltage/current necessary to test the breakdown capability of the MOV WITHOUT DESTROYING IT. A voltage vs current curve of a defective MOV stands out like a sore thumb. > While we are at it, in what cases are MOV's effective--small power surges, > voltage variations caused by large motors, lightning strikes, induced voltage > from lightning, static charges. MOV's are effective in clamping transients from "small power surges", inductive transients from motor starting, and induced voltages from lightning strikes. MOV's are often NOT effective in preventing damage from _direct_ lighting strikes because such transient voltages are longitudinal in nature; i.e., the hot, neutral, and protective ground wires feeding the equipment are ALL raised above ground potential. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York <== ==> UUCP {decvax|dual|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry <== ==> VOICE 716/741-9185 {rice|shell}!baylor!/ <== ==> FAX 716/741-9635 {G1, G2, G3 modes} duke!ethos!/ <== ==> seismo!/ <== ==> "Have you hugged your cat today?" ihnp4!/ <==