|HP 2225D+ RAM failure/replacement|
Message #1 Posted by Luca on 9 Sept 2013, 4:46 p.m.
I have bought a 2225D+ printer that is not working. I have found the servicemanual, where there isn't but I am referring to the 2225C+ model.
The yellow led blinks twice, then a pause, then blinks continously.
All the voltages seem to be ok and the capacitors are ok too.
So, I have done the kernel troubleshooting and I have found a pulse on the cpu's pin #22==>RAM faulty.
The chip is labeled 1LK4-0001 and it should be a 256x4 bit... I think it is a custom chip that has not commercial equivalents neither similar chips with different pinouts...
But how it is addressed?? In a serial way via C/D and STR pins?
All the connections are on a bus wit the ROM chip, so I guess that RAM and ROM have their own addresses...
I can't buy another printer, neither a replacement expensive as gold.
By the way I think that this could be an interesting educational task... is there someone who can explain how this chip work, or where to find some docs, in order to try a replacement with a common commercial chip?