MVF4FS Click of death - some progress

[theangel540]

Hello.
Have troubles with my 4 slots.
green garbage/tiles on screen. Probably, content of the NEO SFIX ROM.
J2/Watch dog jumped with iron for stoping reseting.

I have traced some signals with my scope.
My BIOS/SP1 want to boot a fraction of seconds (activity on A0, A1, D0, D1...).
I insist of "fraction" of second.
Strange thing: OE is alway LOW (+vcc > inverted input). OE MUST pulse like AO, A1 etc ...
On the MVF4FS, OE is routed in NEO-E0 (output pin 59).
there is an AND gate inside (?) pin 60 + pin 61. these are HIGH (+vcc). OE (pin 59) is HIGH (+vcc) so LOW (inverted) for the eprom.
PIN 60 and 61 are routed to NEO-C1.

PIN 12 and PIN 96 on NEO-C1. All these output HIGH (+vcc) at startup!

NEO-C1 dead ?


Thank for your time.

PS: 68K is new one with support, x4 SRAMs news , work ram pulse.

 

[theangel540]

I presume it's NEO-C1 :-/
don't know how it handle SROM LO and SROM HIGH output ?! boot process of the hardware before seeing crossbar test screen ?
No activity with the 68K

Where to find a NEO-C1 QFP ?

thk.

 

[theangel540]

...Changed the NEO-C1.
Same problem :-(

 

[theangel540]

Changed NEO-C1, NEO-G0, x4 works ram...

Really strange problem on the BIOS/SP1:
Adress lines pulse perfectly.
With the C1 changed, OE pulse some times.
Data lines:
Some have great pulses, some pulse but with tiny amplitude (~1V, we are from TTL levels) :-/
All lines tested between cpu and rom (all ok).