SOLVED - A4000D Rev.B yellow screen together with any Zorro card

drugkito

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Joined
Aug 8, 2016
Posts
519
Country
Croatia
Region
KC
I've got an A4000D rev. B motherboard here that refuses to boot when any Zorro II or Zorro III card is inserted.
Displays yellow screen in a continuous reboot cycle.

When no Zorro cards are plugged in the system works perfectly fine, recognizes chip and fast ram and everything else is ok.
When only the daughterboard is inserted everything is ok as well, just when a card is inserted into the daughterboard it craps out (regardless if only chip simm is there or chip+fast).
Tried multiple known working daughterboards and multiple known working Z2 and Z3 cards.
Tried replacing the buster with a known good one.
Tested the buster chip from this motherboard on the other known working one - chip is fine.

Buster is socketed, so I was thinking of either replacing the socket or soldering down the buster, but before I do that, does anyone have any idea on what else to look into perhaps?
Socket does look a bit dodgy but traced all the lines from the socket and they also appear to be ok.

Searched around the forums *a bit* but the only similar problems I could find were either related to bad simm sockets/traces/modules or buster chip/socket.
Anyone had a similar situation?
 
Last edited:
I had an A4000T that refused to work with Zorro III cards. Fault was traced to one of the 74FCT16646 bus transceiver chips. The A4000D uses 74FCT646 and 74F245 chips for this application.
 
Removed the dodgy socket and soldered the Buster directly to the motherboard.
All good now.
 
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