Crazy Transformer question

[Zane H. Healy]

>  > OK, this is a really bizarre question.  My Neo-Geo arcade has been
>>  acting up, and a couple weekends ago when I tried to take a look at
>
>Define 'acting up', please.

After an hour or two the display would go all weird, and shaking like 
crazy, or a couple times the picture simply disappeared.  Then like I 
said, a couple weekends ago, I didn't even get a picture on the tube, 
yet when I'd power the system off it would flash some color.

At the same time I'd get the system music just fine (or game sounds, 
and even game play when it was just shaking).  So it seemed to be 
totally restricted to the monitor portion of the system.

>  > it, I couldn't even get a picture.  Today I got the bits to take out
>>  the security screws so I could get into the part where the
>>  powersupply is.
>>
>>  It was just up for 4 1/2 hours without any problems.  The only things
>>  that have been done is to wipe the grill where the fan is off (it was
>>  really filthy), and to move an old sewing machine that was sitting on
>
>Could it be that the machine was overheating? Or that you re-seated a
>dodge connector when you had it apart. Or disturbed a dry joint?

I'd actually considered the overheating part based on how filthy the 
grill on the powersupply was, but since the previous time I couldn't 
even get a picture, I rather doubt it was overheating.

This last time, it worked without me touching a single wire.  All I 
did was move the system, take the back panel off (couldn't do it last 
time thanks to security bits), and clean the transformer grill.  I've 
a bad feeling that there is something in there that is a loose, or 
that there is a dry joint, and whatever it is has been disturbed, and 
then fixed, by moving the system so I could get at the back of the 
unit.

Last night it ran for about 4 1/2 hours straight, and before that it 
probably ran for 30-45 minutes with me turning it on and off a few 
times.  Today it's been on for about 15 minutes so far.

>I don't see how. It's possible for the stray field of one transformer to
>couple to another (valve audio amplifers nearly always had the cores of
>the mains and output transformer at right angles to reduce hum, for
>example), but I've never heard of stray fields or metal affecting a mains
>transformer.

I didn't see how this could be it either, but wanted to double check 
and make sure I'd not forgotten something.  It's been a *LONG* time 
since I studied transformer theory, and I've never claimed I was a 
good electrician :^)

			Zane

-- 
--
| Zane H. Healy                    | UNIX Systems Administrator |
| healyzh at aracnet.com (primary)    | OpenVMS Enthusiast         |
|                                  | Classic Computer Collector |
+----------------------------------+----------------------------+
|     Empire of the Petal Throne and Traveller Role Playing,    |
|          PDP-10 Emulation and Zane's Computer Museum.         |
|                http://www.aracnet.com/~healyzh/               |