Home▸ Forums▸ 68kMLA▸ 128k logic board problem — #23
Post #23 by gooddi
Source Forum68kMLA
CategoryTroubleshooting
Post DateSun, 28 Jun 2015 - 14:13
Original URLhttps://68kmla.org/bb/threads/128k-logic-board-problem.2141/
Post
techknight said:
you forgot the 74F253s. Those are the muxes for the row/column address strobes for the RAM, if those are bad, youll get this screen as well as sad macs, depending on which ones bad. 

Also, Keep in mind you may need to start looking at the PALs. These machines are old enough that if they were stored in a moisture laden environment for 30 years, they will seep through the epoxy and start attacking the silicon die, and you get this.... 
Click to expand...

thans for your very useful information.

i will investigate 74F253S.

and which one is PAL ? Please tell me more about PAL.

did you mean ASG? i can't find PAL on my logic board.

WIKIPEDIA say that about PAL

 - BMU0/1, TSM, TSG,LAG,.....

RIGHT?

Thanks again, techknight. :)

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