SB-610 Experience

[Peter A Markavage]

The primary side already has fuses. The transformer has both HV (low
current) and lower voltage windings. If the HV circuitry shorted, mostly
likely the high voltage winding would open before the primary side fuse
would go. With approx.1300 to 1500 volts on the HV side, depending on the
monitor scope, I guess I would prefer a wire type fuse rather than a LED.
Much smaller surface area, where as LED's have plastic and silicon to
burn in case of a short.
Pete

On Fri, 1 Aug 2003 08:43:54 -0700 Kinney John-r17512
<J.Kinney at MOTOROLA.COM> writes:
> How about putting the fuse on the primary side of the transformer?
> All you need to know is the step up or down ratio, i.e. 120VAC to
> 600VAC is 5 times.  Ohms law says the power is the same on both
> sides (give or take a little), so if you are using 10 mA on the
> output at 600VAC then you are using 50 mA on the input at 120VAC.
>
> I have in the past used an LED for a fuse.  In the AC circuit I used
> a Bi-Colored LED (two LEDs in parallel with opposite polarity) that
> had a maximum current capacity of 30 mA.  This worked very well for
> trouble shooting also as the intensity would change with current
> changes.  Certain light bulbs would work equally well, as someone
> else on this list has already mentioned.
>
> 73's
> John KA7CVJ
>
> -----Original Message-----
> From: Mark Graalman WB8JKR [mailto:wb8jkr at JUNO.COM]
> Sent: Thursday, July 31, 2003 2:02 PM
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: Re: SB-610 Experience
>
>
>   I'm not sure but I would think the HV secondary may only
> be rated at about 10 ma. or so and the smallest fuse I've
> seen is about 100 ma. Anybody know what the secondary
> can really tolerate current wise?
>
> Mark  WB8JKR
>
>
> On Thu, 31 Jul 2003 12:06:59 -0400 Peter A Markavage
> <pmarkavage at JUNO.COM> writes:
> > Has anyone considered a small low current fuse or a fusible link
> in
> > series with one of the secondary high voltage leads. Given that
> > exact
> > replacement power transformers are not readily available and
> since
> > the
> > high voltage secondary winding can be under a lot of stress, due
> to
> > component aging or leaky or possible shorting of the .15 mfd
> > capacitors,
> > some means should be provided to protect the HV secondary. I seem
> to
> > recall running across computer monitors and some small portable
> TV's
> > that
> > used fuse links to protect their HV secondaries.
> > Pete, WA2CWA

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