My first Vic has been dead with a black screen since the end of the 80s but recently I've used the 'dead test' mode of the Penultimate+ cartridge http://blog.tynemouthsoftware.co.uk/201 ... -plus.html and amazingly, the test runs, and produces a test result showing a fault in 'RAM 0' bits 4-7. Just like the TOP LINE of this image (but IGNORE the KERNAL line as this is a sample image from the manufacturer's website) :-
It's an early VIC (not a CR version) and has 11 chips of HM472114P-3... I think the 'dead test' result means that the fault is one of these 11 RAM ICs, which I think means the pair of RAM chips covering the VIC's 6502 address ranges 0-1023.
But now I'm stuck... which physical chip is this on the PCB?
Do any of the experts here know which IC I need to change???
Dead VIC resurrection
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- mrr19121970
- Vic 20 Nerd
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Re: Dead VIC resurrection
Interesting.... I thought the concept of an external kernel was not possible
Re: Dead VIC resurrection
Assuming it's an original PAL then the section of the circuit diagram of interest is http://www.zimmers.net/anonftp/pub/cbm/ ... 4001_3.gif
The diagnostic seems to indicate the fault memory is bits 4-7 of RAM0 so the chip to replace should be UE2.
The diagnostic seems to indicate the fault memory is bits 4-7 of RAM0 so the chip to replace should be UE2.
Re: Dead VIC resurrection
I'm guessing that the image was created on a system when the original system ROM was physically replaced by the diagnostic image.mrr19121970 wrote:Interesting.... I thought the concept of an external kernel was not possible
- topcat
- Vic 20 Drifter
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Re: Dead VIC resurrection
Many thanks! I agree this suggests this IC. I think I''ll also check the CS line on an oscilloscope, and solder in a socket for UE2.srowe wrote:Assuming it's an original PAL then the section of the circuit diagram of interest is http://www.zimmers.net/anonftp/pub/cbm/ ... 4001_3.gif
The diagnostic seems to indicate the fault memory is bits 4-7 of RAM0 so the chip to replace should be UE2.
- topcat
- Vic 20 Drifter
- Posts: 26
- Joined: Fri Dec 16, 2016 12:57 pm
- Location: London
- Occupation: Broadcast R&D
Re: Dead VIC resurrected!
I have good news to report!
The Chip Select line looked messy on a 'scope, but compared with a working VIC it looked very similar. That could easily have led me down the wrong path. I bit the bullet and snipped off each leg of UE2, and then de-soldered each leg individually. I cleaned up and soldered in a dip18 socket. I inserted an HM472114AP-2 into the socket as I couldn't source an original HM472114P-3. Looking at the datasheet, the AP-2 appears to be a slightly faster version of the original Commodore fitted P-3.
And... my VIC works again! 3583 BYTES FREE !!!
Thanks to user 'srowe' who helped locate RAM0!And thanks to Tynemouth software for implementing their 'dead test' mode!
The Chip Select line looked messy on a 'scope, but compared with a working VIC it looked very similar. That could easily have led me down the wrong path. I bit the bullet and snipped off each leg of UE2, and then de-soldered each leg individually. I cleaned up and soldered in a dip18 socket. I inserted an HM472114AP-2 into the socket as I couldn't source an original HM472114P-3. Looking at the datasheet, the AP-2 appears to be a slightly faster version of the original Commodore fitted P-3.
And... my VIC works again! 3583 BYTES FREE !!!
Thanks to user 'srowe' who helped locate RAM0!And thanks to Tynemouth software for implementing their 'dead test' mode!