Some questions on a Mario Bro cabinet / Sanyo 20ez

[rassilon]

So I just came into possession of my first cabinet, Mario Bros, and am in the process of trying to get it working again.  It worked for awhile then stopped (monitor is blank) so my coworker told me I could have it if I hauled it away).  I did some basic digging and (thanks to a flow-chart I found online) have traced at least the initial problem to the HOT on the monitor pcb (my F301 fuse was getting blown on powerup).  I pulled the HOT out and checked the signals with my meter (registering a .001 and .084 on the two pins).  So my question(s) are:

1) What would the appropriate replacement part for a Sanyo 20ez hot (I believe this is Q902?).  I've looked at a couple of sites but none of them seem to say "Hey, this is what you need to replace the hot in a 20ez".  What was there was labeled as an 1870.
2) It looks like the flyback is ok (no visible cracks, though I can't say for certain there isn't an issue there as well).  Is there a way to test this?  Based on the underside of the board I think this may have been replaced at some point but I'm not certain.  I can tell by some lackluster solder work that the thing has been at least partially re-capped at some point.
3) Anything else that would make sense to check prior to ordering a new HOT?  From the flowchart I found, it seems the likely culprit is a bad HOT(which I've determined to be bad) or the flyback.

Lastly, as a safety question.  I was watching John's video of capping a 20EZ (great timing BTW!) and noticed his 20ez had a metal shield case around the flyback.  Mine does not (it also doesn't have the inverter board but since it was working I'm going to assume that's ok).  How much of a safety issue is not having that metal shield around the flyback going to be?  Someone told me it was there to prevent potential electric arcs and getting zapped while adjusting the pots so I'm trying to determine if I need (or should) track a replacement cover down.

Any thoughts/suggestions appreciated.  I have pretty limited experience working at this level of a circuit board but I'm willing to learn/test/figure it out.  I'm excited to be getting into the hobby!

Thanks!

[iankellogg]

Sounds like the hot is bad. As far as replacements, there are 3 drop in replacements listed on the schematic and there quite a few alternatives that can be used.

The three listed replacements on the schematic are
2SD869
2SD898A-05
2SD993A


Dont bother replacing the flyback until the hot is replaced. I am a firm believer in only replacing what is broken.
Another thing you should check is to see if the vreg is working properly and you are getting 108VDC at a B+ test point. If this is 130VDC then you may have a bad vreg IC or transistor.



The metal shield on the flyback isn't required, its a safety and noise shield but is not 100% required for operation. just don't go sticking your hand around the flyback when its on.