Hantarex MTC-90 to MTC-900 Conversion completed

[PaulSwan]

Hi,

Finished writing up this conversion project that turned out pretty good:

http://www.paulswan.me/arcade/HantarexMTC90MTC900Conversion.htm

The 900 has a better picture than the 90 (that I was never able to get anything more than average out of).

Observe the screen shot from Astro Wars - there is an analog effect in use that I've never seen before and was also present on the 90 but I didn't look closely enough to notice it. I don't yet know how this effect is implemented other than there is mixing into the sync signal that seems to have something to do with it... I'll leave it as a quiz to spot it

http://paulswan.me/arcade/tech/HantarexMTC90MTC900Conversion/DSCN3929.JPG
http://paulswan.me/arcade/tech/HantarexMTC90MTC900Conversion/DSCN3963-1.JPG

Paul.

[Etienne MacGyver]

Nice write up Paul 

Thanks for sharing, its an interesting read !

Its great to have a option with a MTC-900 chassis on a MTC-90.

Those MTC-90 chassis with theyre "card setup" are a nightmare !

[Belike]

Nice technical overview and excellent job!
I also had to change the dead MTC90 in my Super Galaxian, but I chose the easier way, replaced the complete monitor with frame and put a Hantarex 900E with a stepdown converter in it.


https://www.dragonslairfans.com/smfor/index.php?topic=6271.0

[philmurr]

Very interesting read Paul.

The only bit I'd be worried about is where you've used zeners to do the volt drop, they can give pretty spectacular effects when they fail 

But very impressed with what you've done

[PaulSwan]

tbh I'm not sure if the 13VAC drop is really needed - I measured the IGR supply I'm using on my bench (intended for 900E) and it was 143.5VAC under load for the 128VAC.

With the Zeners in line like that, it's doesn't have a catastrophic outcome if they fail open or short. After 14 hours running yesterday they were still OK to touch temperature-wise. This method of AC adjustment is a bit of an experiment and it might end up in the Bad Circuits section in The Art of Electronics

Paul.

[PaulSwan]

No one's spotted the analogue video effect? Need a clue?

"All pixels are created equally... ...or are they?" 

Paul.

[vernimark]

 
this is really a great job!

Now I gave just a fast look but be sure I'll need to study all the process deeply soon (just the time next MTC90 will fire up!)

 

[PaulSwan]

Yeah, I'm doing them as they break down. The Sea Scare MTC90 was still running by the end of the last show though the picture quality is pretty poor on it.

Another clue on the analogue effect - the characters display in small square pixels, the stars & shells display in large round blobs. I think it's a combination of the inverted video design, the chassis and the CRT that causes it.

Paul.