RE: Pole Position monitor blowing fuse

Here's a tip when the fuse blows. If the fuse just opens after a while,
then something is slowly drawing too much current. (Fuses can open just
from old age/metal fatigue, without anything really being wrong with the
rest of the circuitry.) But if the fuse blows INSTANTLY, with a bright
flash, and splatters the inside of the fuse glass with black stuff, then
there's a dead short somewhere.

Matt J. McCullar
Fort Worth, TX

-----Original Message-----
From: owner-rasterlist@vectorlist.org
[mailto:owner-rasterlist@vectorlist.org]On Behalf Of John Robertson
Sent: Saturday, April 17, 2010 11:14 AM
To: rasterlist@vectorlist.org
Subject: Re: RASTER: Pole Position monitor blowing fuse

Christopher X. Candreva wrote:
> I've got a Matsuhita TM-202 in my Pole Position that is blowing
> Fuse F002 . In 2005 I replaced the flyback and recaped this monitor.
> And -- that's about all I know.
>
> I know my way around vector monitors, but where do you start on a raster ?
>
> ==========================================================
> Chris Candreva -- chris@westnet.com -- (914) 948-3162
> WestNet Internet Services of Westchester
> http://www.westnet.com/
>
>

Hi Chris,

Well, the first thing to check is if the horizontal output transistor
(HOT) is shorted. You need to remove it or unsolder the emitter and base
leads to check that out. If it is shorted then you need to check if the
flyback is good or bad - I happen to sell an in-circuit flyback tester
that can help here ($42US), and it is good for testing flybacks in both
raster and vector monitors...(sorry about the ad) or you can borrow one
of these from someone on this list - we have sold a few to regulars here.

I find that the flyback or HOT fail from capacitors breaking down - a
good argument for checking caps every now and then for signs of heating
up (plastic film on cap appears to shrink back from covering 1/3 of the
top of the cap) or monitor changing size, etc. are clues that it is time
for recapping. Many recap kits are using inexpensive capacitors that do
not meet factory standards for ESR charateristics - I found Competative
Products kits to be poor in this area and we would replace a couple of
their caps with better rated ones as required in the horizontal section
of the monitor. Caps with low high ESR tend to fail faster and load the
circuit down more than caps with low ESR.

Of course the blown fuse could be simply a shorted diode on the primary
B+ supply...

John :-#)#

--
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com
"Old pinballers never die, they just flip out"
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