MV4-FT2 blank screen

raulos

Pupil of Bonus-Kun
Joined
Jun 30, 2018
Posts
7
I have this non booting 4 slots motherboard. After power on it shows just blank white screen and no response whatsoever. Checked board for any broken traces, checked pallete ram and 68k with logic probe and everything seemed to be more or less fine. Lastly i ran diagnostic bios and i received message like this:
"MMIO DEAD OUTPUT
ADDRESS: 320001
1st gen: (no info)
2nd gen: NEO-C1(2) <-> NEO-F0(34)"
What should i do next?
 

ack

B. Jenet's Firstmate
Joined
Apr 9, 2009
Posts
410
I would also check hard dip 8, and make sure its off
 

raulos

Pupil of Bonus-Kun
Joined
Jun 30, 2018
Posts
7
Check the LO CHIP
BB
And again all traces are good. There is a connection between L0 and LS245 (through data output 0÷7); NEO-I0/NEO-LSPC2 (through P0÷P14 bus). Trace that enable L0 output is good as well.
I don't know if it's important, when i tried 'calendar i/o' option in unibios menu it stucked on "waiting for calendar pulse".
 

raulos

Pupil of Bonus-Kun
Joined
Jun 30, 2018
Posts
7
SFIX is connected to NEO-I0, B1 and LSPC (from pin9). So again, no luck.
 

raulos

Pupil of Bonus-Kun
Joined
Jun 30, 2018
Posts
7
This board begins to drive me insane 🤯
I double checked continuity traces from and leading to chips mentioned above. What does exactly dead mmio output means? I did input test and no reading on P2 B and C button. Checked all the way from jamma connector through resistors ladder to NEO-C1. Inspected connections from NEO-C1 - - > 68k and NEO-E0. No sign of broken trace.
halp :)
 

ack

B. Jenet's Firstmate
Joined
Apr 9, 2009
Posts
410
Its doing a read test on a handful of the memory mapped registers. The diag bios is able to detect if the read never returned any data, hence the DEAD OUTPUT error message. In your case the address it was reading from was 0x320001, which is this


If you haven't do so yet I would also try doing manual tests with the diag bios and see if it shows any other issues that may help. You can bypass automatic tests and get to the main menu by holding down A+B+C+D when you power on the board. Its possible this wont work for you if its unable to read 0x300000 (REG_P1CNT).
 

raulos

Pupil of Bonus-Kun
Joined
Jun 30, 2018
Posts
7
Im back after some while. I tried to go through ram tests but every single test takes ages. They go much faster on my second (mv2) board which i use as a reference. Btw is the stock bios for mv2 the same as for mv4 board?
Assuming that culprit can be clock circuit - no pulse signal from d4990 in diagnostic calendar test and REG_STATUS_A also is refers to RTC i replaced d4990, hc32 and both crystals. Still no luck. I checked NEO-D0 pins responsible for different clock signals and i got pulse (without H/L reading on logic probe) on pins 21,22,23,27 and 28, H+L+pulse on 24. Strange thing is happening, when i put logic probe on pin 19 i got L+pulse and board resets. On 18 i got just pulse.
 
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