NEO-MVH MV1FS Screen error

[r67055]

Hi !

I want to ask for help.
after the green boot screen i see this picture.... Where should I look for the error on the board...I feel like this image would be an error message, but that’s not the only way you can display it..
Thank you in advance for your help!!!

 

[channelmaniac]

In the hundreds of Neo Geo boards I've repaired... I've never seen that screen!

What do you get when you turn all 8 of the DIPs on and boot the game?

 

[r67055]

if I turn all these switches to ON, it will give such an image

 

[r67055]

If I take out the CXK5814P it gives such a picture

 

[channelmaniac]

if I turn all these switches to ON, it will give such an image

OK,

That big green blob should be saying "WORK RAM TEST" in double height characters. Seeing a big green box tells me you need to replace the surface mount Video RAM or check the pins on the LSPC2 chip.

 

[r67055]

OK,

That big green blob should be saying "WORK RAM TEST" in double height characters. Seeing a big green box tells me you need to replace the surface mount Video RAM or check the pins on the LSPC2 chip.

thanks!!

 

[r67055]

it is not an easy task to check 100 pints, but unfortunately I did not find any signs of error.
Unfortunately I don't have another LSPC2 chip in my possession to replace, but I wouldn't have the tools to replace it either

 

[channelmaniac]

If those look OK, replace the surface mount Video RAM.

 

[ic3b4ll]

I don't know if this will help, but if the FIX ROM is bad you'll have all sorts of glitches (repeated characters, squares etc). I've seen something similar in the past and it was the ROM.

 

[r67055]

thanks for joining me for more help.
Parts will arrive on Friday so I can replace parts

 

[r67055]

hi again!
a new motherboard has arrived, which is also bad!
I replaced the TC 531024 ROM from it
but unfortunately no change has taken place.

 

[r67055]

I was a little insecure. which motherboard should I start repairing?
The new motherboard displays a Calendar error on the screen due to the 0V battery, but unfortunately here too, there is a display problem.

The picture jumps

 

[r67055]

on first start as I tried, the image didn't run!

He showed a Calendar error screen.

 

[channelmaniac]

Calendar error = system cannot read the clock/calendar chip.

Look for damaged traces around the 74HC32 and the battery backup. You probably aren't getting +5v to pin 14 of the calendar chip because of a battery damaged trace.

That would also explain the jumping screen and the third picture with just garbage - you probably have one or more dead traces around the 74HC32 and between it and the Backup RAM. When the enable traces and the R/W signal traces for the Backup RAM get damaged the RAM will output data spuriously to the data bus causing the CPU crash.

 

[ic3b4ll]

@channelmaniac Don't you think the clock divider and/or 24Mhz crystal may be faulty? It would explain the stretched pixel effect you see and would cause a calendar error because of the timing check mismatch.

 

[channelmaniac]

I've never seen that failure in the hundreds of NG boards I've repaired. Could be a first... but it's easy enough to check with a modern oscilloscope or frequency counter that will show you a count of the frequency. If you have an old-school scope you can take the timing period the horizontal timebase is set to and calculate the frequency manually.

 

[r67055]

Unfortunately, I don't have an oscilloscope
but I can replace the 24Khz quartz from the other motherboard

I replaced the 74HC32 ic today, but unfortunately it didn't solve the problem.

And of course I replaced the battery that was completely discharged

Now I'm starting to change the quartz for him.

 

[r67055]

wow ...
I managed to solve the garbage picture problem !!!
The quartz exchange brought results!

 

[channelmaniac]

Did you check the traces around/under the HC32 while you were replacing it?

Have you verified +5v on pin 14 of the clock/calendar chip with power on?

 

[ic3b4ll]

I've never seen that failure in the hundreds of NG boards I've repaired. Could be a first... but it's easy enough to check with a modern oscilloscope or frequency counter that will show you a count of the frequency. If you have an old-school scope you can take the timing period the horizontal timebase is set to and calculate the frequency manually.

I saw it exactly two times, counting this one.