Re: G-08 rebuild kit

Lewis D'Aubin wrote:
>
>
>> Biggest problem with the monitors 'blowing up' were problems with the
>> ground connections at the power supply Molex pin connections causing
>> bias issues leading to overdeflection and general nasty stuff
>> happening.... If those common/ground connections are beefed up then
>> the Sega/Electrohome monitor is quite reliable.
>>
>> I've done a few upgrades of old Sega games (Star Treks etc.) where I
>> replaced the original power supply with a switcher, and made good,
>> solid (not solid wire!), ground connections between the boards and
>> the monitor and none have failed since - at least no owner has
>> contacted me to fix them since we sold them up to ten years ago.
>
> Hello,
>
> My new Star Trek has a switch mode power supply bolted to the top of
> the burned out linear power supply. I was considering restoring the
> game to factory condition, but with your above comments, I'm not so
> sure I should! Could you detail a procedure for bulletproofing this
> monitor? (I had thought the 'fire' problem lay in the fan blowing on
> the deflection transistors, fanning potential sparks into flame, but
> now I'm not so sure!)
>
> Thanks,
>
>
> -Lewis
>
Hi Lewis,

The problem with XY monitors blowing up is often related to the
ground/common connections between the logic board, power supply and
monitor.

If these connections are all made in a 'star' configuration then the
risk is reduced.

A 'star' connection means that all ground/common lines come to a single
point - and there they are very well connected.

A switching power supply is handy as they normally use small bolts to
secure the power wires to the common voltage point terminal strip.

I recommend the running of a pair of extra common wires (20 or 18
gauge); each separately from the monitor and the logic boards that only
join at the power supply common terminal. If one wire is bolted to the
chassis of the monitor (assuming the monitor chassis is common to the
monitor power supply and video signals), and the second is well secured
(bolted is best) to the logic board common - then these two wires are
bolted to the common terminal on the switching power supply you should
be pretty clear of future voltage caused monitor failures.

Do not use huge wires that may not make good connections, 18 gauge is
just fine - you are just providing an alternate path to allow signal
common reference levels to be as close to 0VDC as possible in case of
connection failures along the power supply common connections.

There are many examples of this sort of common/ground backing up - JAMMA
harnesses have a separate common path for the power supply
voltage/currents and the signals (video and controls) as one example.
Atari logic boards have several ground points - the power comes in one
side, and the signal (speaker, etc.) commons on another. This is to
reduce hum and noise on the screen or audio in raster games.

Pinball machines also have this problem - Gottlieb pinballs in
particular suffered from common/ground errors that I found back in the
80s that also led me to the solution of Sega/Electrohome monitors
burning up in the late 80s and 90s.

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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