Re: G08 F400 Blows

On Fri, 5 Apr 2002, Tim Tewalt wrote:

> Hi again fellas...
>
> I recently rebuilt and recapped a G08 and after letting it warm
> up for 20 minutes or so, F400 blew. It was blown before the
> rebuild but I didn't have any slow-blow fuses so replaced it
> with a 5 amp fast-blow. Just for grins, I popped in a 4 amp
> fast-blow and it fries on powerup.

The fuse should be a 5 amp Slow-blow fuse.
 
> Is there any common component failure or out-of-whack screen
> adjustment that could cause this? I checked the obvious stuff
> like the bridge rectifier, but it all looks OK. The monitor
> appears to work fine until the fuse blows. Nothing smokes, nor
> does any component smell "hot".

I assume you are using the correct transformer, and the tranformer is
putting out the right voltage? Sometimes those input connectors to the
transformers come off and people put them in the wrong location. I
believe they should be on 1 and 3. I would check what voltage input to
the monitor is.

Other than that, I guess take some voltage reading as per the FAQ/Sega XY
manuals. Check the solder joints on the large filter capacitors as well.

I don't believe a screen adjustment will cause this sort of failure.

Looking at the schematics, it looks like there are a few diodes that could
break down and cause a problem. Is the fan and degausing coil hooked up?
Make sure the cap at C401 is 1000uf 80v rated or better. May want to try
replacing diodes D406 and D407 just to be safe (IN4003 diodes).

-- 
Mark Jenison
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