My VIC-1110, which has been circling the earth with me for 37 years, is sick.
Its behaviors are strange, but I've isolated the problem to the $2800-$2FFF memory range (with my 8K RAM starting at $2000).
I'm assuming that this is U2 on the board. Can anybody confirm this? I'd like to get this up and running again, and it would be a simple enough fix if I knew which chip I had to replace. I'm willing to desolder one, but not four.
8K RAM Expander, One Bad Chip
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- chysn
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8K RAM Expander, One Bad Chip
VIC-20 Projects: wAx Assembler, TRBo: Turtle RescueBot, Helix Colony, Sub Med, Trolley Problem, Dungeon of Dance, ZEPTOPOLIS, MIDI KERNAL, The Archivist, Ed for Prophet-5
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Re: 8K RAM Expander, One Bad Chip
Taking a sharp look at the schematic filed at http://www.cbmhardware.de/vc20/vic1110_11.gif: yes - U2 is connected to 1Y1 of U9, which signals the active-low CS when CA11=1A=1 and CA12=1B=0 - which corresponds to the $0800..$0FFF range of the respective BLK.chysn wrote:I'm assuming that this is U2 on the board. Can anybody confirm this?
Good luck!
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Re: 8K RAM Expander, One Bad Chip
Thanks once again, Mike!
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Re: 8K RAM Expander, One Bad Chip
Did the repair work out in the meantime?
If you happen to have a surplus of 2Kx8 SRAMs, you might also consider populating the empty positions, the corresponding stabilizing capacitors and the second DIP switch (though take care to open the jumper pad of BLK2 beforehand). This way you upgrade your 8K RAM expander to a version of the VIC-1111 which can be mapped to any combination of two BLK areas.
If you happen to have a surplus of 2Kx8 SRAMs, you might also consider populating the empty positions, the corresponding stabilizing capacitors and the second DIP switch (though take care to open the jumper pad of BLK2 beforehand). This way you upgrade your 8K RAM expander to a version of the VIC-1111 which can be mapped to any combination of two BLK areas.
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Re: 8K RAM Expander, One Bad Chip
I am a proponent of the 32k upgrade myself. As discussed elsewhere, you can fill in 3 of the 4 empty positions with 8Kx8 SRAMs to get this result.
Be normal.
- chysn
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Re: 8K RAM Expander, One Bad Chip
I just got the chip in the mail. Hopefully I'll have time to put it in this week.
Mike wrote: ↑Sun Jan 26, 2020 2:11 pm If you happen to have a surplus of 2Kx8 SRAMs, you might also consider populating the empty positions, the corresponding stabilizing capacitors and the second DIP switch (though take care to open the jumper pad of BLK2 beforehand). This way you upgrade your 8K RAM expander to a version of the VIC-1111 which can be mapped to any combination of two BLK areas.
I do already have a 32K expander, so I don't need to upgrade this one. I hope to fix it up while keeping it as original as possible.
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Re: 8K RAM Expander, One Bad Chip
Well that's fair enough.chysn wrote:I do already have a 32K expander, so I don't need to upgrade this one. I hope to fix it up while keeping it as original as possible.
TBH, same applies to the VIC-1111 I happened to find (and buy) on a retro fair two years ago.
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Re: 8K RAM Expander, One Bad Chip
Wow, January? Where does the time go?
I completed this repair today. Instead of carefully removing the bad chip (as when I removed a VICmon ROM), I sliced through the pins of the bad chip without regard for it. Unfortunately, I got a little too careless and wound up destroying two solder pads; so I had to go back and make the appropriate connections with some 30 gauge wire. Lesson learned (I need better snippers, beware torsion, etc.) and no harm done.
While the iron is hot, I'm going to install at least one socket in the other half of this thing, so I have more ways to test my EPROMs. I'm thinking that my final unexpanded VIC dev environment is going to wind up on a VIC-1110.
Thanks!
I completed this repair today. Instead of carefully removing the bad chip (as when I removed a VICmon ROM), I sliced through the pins of the bad chip without regard for it. Unfortunately, I got a little too careless and wound up destroying two solder pads; so I had to go back and make the appropriate connections with some 30 gauge wire. Lesson learned (I need better snippers, beware torsion, etc.) and no harm done.
While the iron is hot, I'm going to install at least one socket in the other half of this thing, so I have more ways to test my EPROMs. I'm thinking that my final unexpanded VIC dev environment is going to wind up on a VIC-1110.
Thanks!
VIC-20 Projects: wAx Assembler, TRBo: Turtle RescueBot, Helix Colony, Sub Med, Trolley Problem, Dungeon of Dance, ZEPTOPOLIS, MIDI KERNAL, The Archivist, Ed for Prophet-5
WIP: MIDIcast BASIC extension
he/him/his
WIP: MIDIcast BASIC extension
he/him/his