Posted By
MIK
on 2014-03-29
06:37:12
 |  Re: Suspected PLUS/4 Ram fault
Welcome and worry not about having spares as your not alone. 
In most cases C16/Plus4's can be fixed from a simple chip change as these fail long before anything else soldered to the mother board.
Just some extra pointers as I'm not good on ram...
A black screen can be a dead CPU, sometimes when a CPU dies it also takes TED with it, but not always. A black screen can also be a dead TED but more than likely your actually see something on screen before they totally go, that being a perfect clue TED is failing when you see it. Indeed TED likes to hang-on before it totally dies.
Random characters on screen, normally the TED is failing. Ramdom characters via joystick port, TED is damaged but only related to the joy ports.
Faulty 3+1 roms can lead to the machine locking up as it boots, it may hang on the Basic screen as you switch on and will not allow you to do anything. These roms if faulty can be completely removed for good working or not as they are only software.
When they are plugged in, the Plus/4 is told to look for them, but removed it will ignore the fact they were ever part of the system. "3-PLUS-1 ON KEY F1" will be removed from the BASIC screen if removed and the machine will act like a Commodore 16, but with 64k of memory.
As for RAM I've yet to see a machine with failed RAM so other than changing them for working ones I'm useless. Hopefully the guy Crock will pass by as I'm sure he's good on RAM related issues.
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