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MV1B with Graphic glitches

A

AlBekas

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Aug 29, 2019
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Montreal QC
Hello
Finally, I fried my MV1-b...
Long story short, it happened trying to install an Unibios V4 with a neobiosmasta board. At the same time, I was trying to understand why I couldn't access the Unibios neither the pix'n'mix menus with the sat2neo adapter I have just finished to build and hardly mapped the buttons.
The thing is that I only own a 161in1 cart at the moment, so I can't tell if my issues come from the mainboard, or the cart... And with all this lockdown, it's hard to find a cheap MVS game just to test my board.
Everything was working very well with my minigun supergun before. I removed the unibios but not the neobiosmasta as I am afraid to tear off the IC with the connector, and I reconnected the pad lifted.
I assume the board is back to normal, but still gives me those weird glitches (constant colors where I should see texture) after around 30 sec of game, then getting worse until an almost black screen. Sound is still good though.

Any idea of what can be the cause, or how I can investigate it ?

Thank you very much for your help.
Al
 

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I encounter a board with similar large solid color sprites once before and it was the result of a cut trace to the L0 ROM. The L0 ROM contains the code used for sprite scaling. Something being wrong with it might explain the your first 2 to pictures. I haven't seen anything like your last picture before.
 
Thanks Ack
I tried several things last night : reflow the L0 ROM and other chips not too small for my skills, recap the board (not the sound side), remove the Neobiosmasta board completely, clean entirely with isopropyl alcohol. Nothing helped...
The graphic glitches are still happening after 30-45 sec the MVS is turned on.
 
Ah, that sucks. If you ever give up on this I have a mega fried MV1B that might be saved with guts swapping.

Do the glitches only happen a certain amount of time after power up?
 
Yes, it takes around 30 seconds to happen, weird.
If I power cycle it off and on, the glitches take less time to happen, sometimes almost instantaneous.
 
In that case I suspect your 161 in 1 is the culprit. The earlier revisions only used diodes to step down voltage and that symptom is very likely the cause of that.

Make sure your PSU is under 5v. I recommend 4.75-4.95 when using that cart.

You can see my shaky and difficult to watch video about these boards here:)
 
I checked my 161 in 1 the day I received it ;)
It seems to be one of the last version, with voltage regulators (smaller than the ones in your video tho), and no hot glue.

Like you suggested, I tried under voltage, but no difference (my PSU can't go under 4.82V).
Thanks
 
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