[time-nuts] time-nuts Digest, Vol 63, Issue 101

[gonzo moto]

> Date: Wed, 28 Oct 2009 07:34:25 +0000 (GMT)
> From: Robert Atkinson <robert8rpi at yahoo.co.uk>
> Subject: Re: [time-nuts] 7150+ filter problem
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <989056.10886.qm at web27105.mail.ukl.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
> 
> What you say is true, but there is the time involved in repairing the filter. There is?also the?risk of injury while doing so (those cans have sharp edges), and the risk of a short circuit when the whole thing is re-assembled. I tend to "price" my time these days, I'd rather do something to raise ?25 (overtime, put something on ebay) than spend 2 hours messing with a smelly mains filter. If you want minimum cost, bypass the voltage selector and fit a standard filter inlet with an adaptor plate.
> ?
> It's very much a personal choice.
> ?
> Robert G8RPI.
> 
> --- On Tue, 27/10/09, David <t_list_1_only at braw.co.uk> wrote:
> 
> 
> From: David <t_list_1_only at braw.co.uk>
> Subject: Re: [time-nuts] 7150+ filter problem
> To: time-nuts at febo.com
> Date: Tuesday, 27 October, 2009, 23:20
> 
> 
> > 
> > 15 minutes is all it took for the signature ffffffzzt pop of 
> > the filter letting go.
> > 
> > It has (to say the least), forced the issue.
> > 
> > Now I've removed all the solder around the earth pin, but I 
> > still can't get the cover off. Does it just require brute 
> > force to pull it off or there something else holding it on?
> 
> >> never taken an FN372 apart, not really worth it as?they are 
> >> about ?25 from RS components. Most filters are epoxy potted 
> >> so I think you will have to use a lot of brute force to open 
> >> it up and then break up the epoxy.
> 
> I went the brutal route, I think I 'peeled' the metal (in strips) off the
> potting and then just cut everything out from the back until I found the
> three pins. As for is it worth fixing, when I've fixed something I know how
> it's been done and who is to blame next time. Besides, ?25 for a mains
> filter is painful when the whole meter cost ?20 via fleabay - it's one of
> those Scottish things.
> 
> David
> GM4HJQ
> 
I hear you David!

I thought I'd start on the working filter and the repair the smoked unit when I know what I'm doing.

I've burrowed inside the filter and was surprised to find the filter caps (WIMA MP3-E) are only rated for 250V.
The MP3-E is a discontinued line (read: I can't find a datasheet).
These might be ok for European 220V, but my UPS shows my line voltage to average 243V, with regular excursions over 250V.
These caps may be good, but I'd like to see a bit more margin there (it'll be going back together with MP3-X2/275V caps).

Robert, while it's not that I don't value my time, my workmanship is up to the task, and I'm reluctant to replace a component (possibly with one no better than the failed part) when I can fix it better than it was in the first place. 

ian
 		 	   		  
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