Vic 20 Charcter ROM EPROM PCB adapter

Discussions for CBM PET, VIC-20, SX64, C16/+4 and Commodore 128 systems
nama
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Re: Vic 20 Charcter ROM EPROM PCB adapter

Post by nama »

Here is the cut trace...very small cut right by the pad. I always cut by the pads incase I want to bridge the cut it's easier and less obvious.
Cut.png


banman
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Re: Vic 20 Charcter ROM EPROM PCB adapter

Post by banman »

Hi nama,


That's a fine job there! I've learned a new useful trick today.
I saw your YouTube post as well ...

https://github.com/svenpetersen1965/VIC ... 0vseJkMHag

Looks likes it's only gone up in the last 5 days. Yes, his wiring is the same as yours. I wonder if one is better than the other?

The adapter has a short front suitable for the NTSC Vic 20 CR cost reduced machines.
nama
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Re: Vic 20 Charcter ROM EPROM PCB adapter

Post by nama »

Yes, I saw Svens post about his adaptor on the Vic20 Facebook page a few days ago. Timely.
So just to confirm your fix, are you connecting OE on the 27512 to both CE1 and CE2 on the 2332 side.
Electrically speaking, either way I can't see it making any difference at all.
banman
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Re: Vic 20 Charcter ROM EPROM PCB adapter

Post by banman »

Hi nama,



svenpetersen1965 has some really nice projects.

nama wrote: Sat Jul 24, 2021 7:36 am So just to confirm your fix, are you connecting OE on the 27512 to both CE1 and CE2 on the 2332 side.
Electrically speaking, either way I can't see it making any difference at all.

Maybe the wiring order doesn't matter.

Regarding my wiring of this PCB I basically have the wiring the opposite to yours.


So, in my version I have the Vic 20's 2332 socket pin 21 /CE2 connected to pin 22 /OE of the 27C512 EPROM. Pin 20 /CE1 of the Vic 20's 2332 socket connects to pin 20 /CE of the 27C512 EPROM.
It appears like I have left pin 20 and pin 22 connected on the 27512 to pin 20 /CE1 on the 2332 side when looking at the bottom of the PCB. What I have in fact done is I lifted the socket leg up of pin 22 where 27c512 EPROM sits and connected the red jumper wire. I added a turned pin socket to the end of the red wire to act as a plug.
This way I can switch between a standard C64 ROM configuration (the way the PCB was originally intended) and the Vic 20 Character ROM configuration the mod we have done.
When you see this blob of hot glue on the side of the socket it's actually covering the lifted socket pin and the red wire is soldered to this lifted pin.
Your modification is way better than my hack.
IMG_20210724_191647.jpg
CM201112-203014003.jpg
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