Why not remove the blown unkown Metal Oxide Varistors in the
PSU unit and get an external Surge-protector with (new) varistors
as a frontend to the PSU.
--- European Mains Voltage Adapts slowly towards 230VAC!!!!!!!
Given that the unit seems to need 240 VAC, I guess that the unit operates
in Europe. Over a periode of 10+ years the mains voltage in Europe will
narrow to 230 VAC. This is not likely problematic for equipment that
only has a fairly straightforward powersupply. But for system with surge-
protection it will mean that their protection will either become to sluggish
240v-> 230v. Or worse the protection will trigger to fast if the local mains
goes from 220v --> 230v.
So no matter what the original varistor type was, you may still need to adapt
it to the future mains voltage in europe. By buying a good new separate
surge-protector you will most likely get the right protection for the future.
Remember the mains surge protection only works with a good grounded
earth-connect! We once had a WAN-cable-connect into our router equipment
where the cable-supplier forgot to connect the earth-connect of the overvoltage-
protection-box. Within 1.5 month and two major thunderstorms it killed for
more than $10,000.- of equipment. The cable-boys only came to replace
the burned equipment but never checked the ground system. It took me less
than half an hour to spot the problem. Fortunatly they had to pick up the bill
cause I spotted their ommision !
Sipke de Wal
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http://xgistor.ath.cx
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----- Original Message -----
From: Geoff Roberts <geoffrob_at_stmarks.pp.catholic.edu.au>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, July 16, 2001 9:48 AM
Subject: ZNR Varistor markings
> Hi all,
>
> (And Tony Duell :^)
>
> Have a friends Decstation 5000 power supply with a violently blown fuse.
> (8A/250V)
> He is a developer of VMS Freeware (in fact the WASD web server) and has
> asked me to help.
> Culprit is 2 x ZNR 14K241U devices, which I believe are Metal Film
> Varistors Surge Absorbers.
> The numbering system seems to be obsolete as current ZNR Surge Absorbers
> use a quite different system, or I've guessed wrong and they are
> something else entirely, but I don't think so.
> These two gadgets are wired in series with each other, then connected
> across the output of the mains rectifier.
> 240vac in, so they are across around 300+ vdc.
>
> I could just leave them out and the supply will run, but would much
> rather replace them to keep the protection they offer.
> Their appear to be no other faults and the history of the incident is
> consistent with a switch on surge after an extended holiday (3 weeks)
> following daily useage of the machine, so it's possible the reservoir
> caps may be just a little leaky or the varistor was just getting tired.
>
> Anyone make sense of the device id so I can figure out what rating to
> replace them with.
>
> Device looks rather like a round ceramic capacitor, but gloss black in
> colour, marked with white lettering
>
> A Logo consisting of a small square box in top left with a capital M
> inside and ZNR in caps next to it
> then under it is 14K241U (or the 1's could be ell or i, hard to say).
> underneath at bottom left is an reversed italic capital R with a
> reversed italic capital L joined to the back main bar of the R.
> To the right of this is a small letter s raised above the baseline with
> the number 20 after it.
>
> Any help appreciated.
>
> Cheers
>
> Geoff in Oz
>
>
Received on Mon Aug 20 2001 - 11:48:18 BST