Forum (#50506) - Plus/4 World



	Home Search Games Tapes Covers Cheats Maps Software New Stuff Hall Of Fame HVTC Game Endings Solutions Remakes Publications Magazines Effects Top List Members Groups Features Plus/4 Encyclopedia Hardware Tools Options Forum Home Search Games Tapes Covers Cheats Maps Software New Stuff Hall Of Fame HVTC Game Endings Solutions Remakes Publications Magazines Effects Top List Members Groups Features Plus/4 Encyclopedia Hardware Tools Options Forum	Login

Back to forum

Reply to this topic

Go to last reply

Posted By

YuCalJoe
on 2024-09-18
19:30:29

NEWBIE to Plus4World - Plus 4 question

Hello all. I'm new to this forum.

I have some experience in repairing Plus 4 computers. Probably the easy stuff as seen by forum users such as replacing MT RAM chips with sockets, replacing a bad PLA and socket, and replacing bad Plus4 internal software program chips.

Now here's a weird one for me. I have two Plus 4 systems. The one I've had for a while now had the bad memory chips and program firmware. Easily fixed, and it appears to work just fine. The recently acquired one from ebay had a bad PLA chip which caused a blank screen. I ordered and received a new modern PLA, installed it, and the system booted. I did no further testing at this point. I tested the removed PLA in my Chip Tester Pro, and it failed. So I discarded it.

Then I inserted the diagnostics cartridge into the Plus 4 with the modern PLA, and the cartridge isn't seen. Moreover, the keyboard isn't seen either. So I took the working factory PLA from the other Plus 4system, installed it, and everything works fine.

I next took the new modern PLA an installed it in the Plus 4 that had the working factory PLA in it, and it booted fine. I installed the cartridge, and it and the keyboard work fine.

So when I swap PLA's between systems, they work fine and pass diagnostics (as mush as possible with the harness connected - I have one on order). When I swap them again, the cartridge and keyboard issue returns.

So here's my question. Does anyone have any idea what might be causing this? Both Plus 4's are NTSC.

Secondary question. What is the best version of 264 Diagnostics to burn to a chip (that will be installed on a cartridge board)? The one I have now says "BETA VERSION".

Thank you!

Joe

Posted By

SukkoPera
on 2024-09-19
04:03:26

Re: NEWBIE to Plus4World - Plus 4 question

My first suggestion is to replace all the single-wipe original sockets: PLA, CPU and TED. Those are really bad and tend to create a lot of weird issues, in particulare once you start removing and reinserting the chips. Replace them with modern dual-wipe ones, NOT round machined ones.

Then, if the issue persists, we can dig deeper.

Posted By

YuCalJoe
on 2024-09-19
12:58:51

Re: NEWBIE to Plus4World - Plus 4 question

Thank you for the reply. I will do that with both systems. I'll check the sockets for the ROM chips as well. Then when I get the diagnostic harness in, I'll test both systems and swap PLA's as well.

Thank you!

Joe

Posted By

Csabo
on 2024-09-19
13:17:54

Re: NEWBIE to Plus4World - Plus 4 question

For the diagnostic harness, did you mean Diag264? That one's made by crock, he's around sometimes. The latest version is 0.97, which can be downloaded from his site.

Posted By

YuCalJoe
on 2024-09-19
13:30:25

Re: NEWBIE to Plus4World - Plus 4 question

It looks like I do mean CROCK ((private)).

Joe

Reply to this topic