| Posted By
stufran81
on 2021-12-18
08:51:12
|  Non working Plus 4
Picked up my first Plus 4 but its not working .. it goes to the machine code monitor when turned on.
None of the keys do anything except f1/f2 which prints the work GRAPHIC
Also the screen has like interference that comes and goes.
Probably a multitude of things to fix on it , loll
Anyway I'm going to start with a clean up and recap first. If that doesn't fix things what am i looking at trying next ?
Any ideas
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Posted By
javierglez
on 2021-12-19
12:53:42
| Re: Non working Plus 4
I'm not into fixing things but IMO a recap won't fix anything, it's usually ICs to blame.
If it's booting into the ML monitor instead of BASIC, my guess would be faulty RAM. It may be ROM too, I don't know the startup sequence really.
For the partially working keyboard it's usually a VIA/CIA on VIC20 and C64, here I don't know but probably some IC too.
Cleaning is not a bad idea, carefully remove the chips from the sockets and check there's no rusty or bent pin etc
Good luck
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Posted By
MIK
on 2021-12-19
14:19:32
 | Re: Non working Plus 4
Could be the 3+1 software roms, if it finds a fault with these while booting up it can dump you into the monitor.
Thankfully they can be taken out and left out..., if your problem turns out to be the 3+1 roms your Plus/4 will look like a C16 with 64K on the BASIC screen. Some people take them out anyway as they don't use the software and it can save having extra heat inside the machine from powering them.
3+1 HIGH Rom
hardware/C317054-01
3+1 LOW Rom
hardware/C317053-01
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