Sick Plus/4

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Sick Plus/4

Post by Plus/4 »

When I boot up my Plus/4, the screen has flashing blocks,<, and 0's. It displays "Commodore Basic 3.5" but not "ready" and the keyboard will not respond. I cleaned and reseat the IC that were in sockets and checked for shorts in the ic pins. I did notice that u19 was warm to the touch as was the cpu, u2. Can any one help?
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Post by administrator »

This chart MAY be of some assistance:

Keyboard does not operate correctly when system warms up
Keyboard is unresponsive
Last edited by administrator on Sun Nov 13, 2005 7:57 pm, edited 1 time in total.

Sick Plus/4

Post by Plus/4 »

Does U19 normaly run hot like the cpu? Where can I get replacement parts (roms & PLA)? Rams are still available. Is there a genaric replacement for the roms and PLA?
Bil Herd

Heat and breakage

Post by Bil Herd »

Without remembering what U19 is I would say it is normal for all chips of that era to get as hot/warm as the cpu (of that era). If you can keep your finger on it, it may not be "too hot" (I had a scar on one finger during the winter of 84 from a chip that was burning up, you could actually make out a little TI emblem backwards in the color of the burn).

Basically if you got half a boot and not the rest it would generally mean the processor walked off on ya at some point, I can't think of anything specific where something like a voltage needs to be there to finish booting (C128 could blow a fuse on the 9vac and still work sort of), could be bad Ram, bad Rom, or bad TED, bad processor or really anything connected across the data/address lines.

I gotta believe that an EBAY Plus4 is cheaper than parts replacement. :/

Let me know what fixes it. (

Bil Herd

Sick Plus/4

Post by Plus/4 »

Thanks for the reply.
U19 is a PLA. I would expect the cpu and ted to be warm but not sure about the PLA. Just useing the cpu as a reference. Ebay plus/4 go for $20-$40. I might move the ram chips around and see if any symptoms change.
I have branded IC's logos in my finger before.
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Joined: Wed Aug 30, 2006 1:26 pm

Post by DarthKur »

Sadly, I'm in the same sort of situation and for the second time in a row. I have two Plus/4's that will not function properly. The first one doesn't even boot up. It just displays a scrambled multicolored screen. The second one does that too but will boot, sometimes, with the depression of the reset button repeatedly. Most of the time letters and numbers are either placed out of order or on different lines or just a mass jumbled mess. When it does boot to the proper "ready" status it generally does not stay working for long. Even the most simple tasks, such as calculator functions and print statement's usually end up with a return of either incorrect data or several lines of nonsensical letters. That or it locks up. Even my C16 doesn't work perfectly. It will sometimes return garbled and/or incorrect data. Or even when sitting inactive it will spontaneously print out several odd lines of mixed up code.
Where these machines made with sub par materials or am I just very unlucky?
The world has moved on and left me behind. Therefore I choose to retreat into the past.
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