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Posted By

vigsa (HUN)
on 2008-12-26
09:37:52

Missing BASIC ???

Hi,
I've just got a "new" PLUS4 for XMAS. I was wery happy to get one after so many years. Unfurtunately it doesn't work. When I switch it on, the blue frame and a the white screen appears, and the cursor is in left-top of the screen. But no welcome message, and no "ready". When I press "Run Stop" and reset, I can reach the assembly interpreter. Everything works (typing, listing memory, etc) but when I want to exit to BASIC (with X) then it stops working.

Can somebody help me, please?

Posted By

Rachy
on 2008-12-27
03:04:54

Re: Missing BASIC ???

As it seems the initialization procedure stopped somewhere, you might try to remove the chips which are in sockets clean the socket and push them back again.

Posted By

Gaia
on 2008-12-27
05:41:45

Re: Missing BASIC ???

First candidate being the BASIC ROM:

C318006-01

Posted By

vigsa (HUN)
on 2008-12-27
12:13:59

Re: Missing BASIC ??? -> Buggy BASIC ROM?

First of all, thanx for the tipps. The motherboard and the chips/sockets are now clean, but the problem still exist. I Found a new sympthom: when I list the contents of memory at the address of 8000 it does not seems to me allright. It changes! (M 8000, D 8000) For example: M 8000 : F0 F0 F8 F0 F0 FC F0 FF. After 3 sec, M800 : F0 F0 F0 F0 F0 FC F0 FD. I tried other memory addresses, but only 8000 and above are changing. When I look at the code (D 8000) it is not like a healthy program.
Any other idea?

Question #2: Basic should start with G 8000, isn't it?

Posted By

Rachy
on 2008-12-28
03:13:31

Re: Missing BASIC ???

That content for address $8000 is wrong. As it seems either the BASIC ROM chip or the 3-plus-1 chip is broken. You might try to remove the 3-plus-1 chip, which is useless anyway.

Posted By

vigsa (HUN)
on 2008-12-28
19:21:44

Re: Missing BASIC ???

Sorry, but which one is the 3-plus-1 chip?

Posted By

Rachy
on 2008-12-30
04:46:58

Re: Missing BASIC ???

I have removed them from my Plus/4 a long time ago, so I don't know the exact chip ID numbers, but the two which marked on the motherboard as U25 and U26.

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