๐บ๐ธ Commodore VIC-20 Refurbish: Part 3 (Replacing ROMs)
27We do some further work on this VIC to reduce its current draw and waste heat. The stock VIC draws about 1.17A but after replacing the LM323 regulator in Part 2, and now the character & kernel ROMs with 27Cxxx EPROMs we were down to 940mA. Both ROMs will also run much cooler now.
We also look at replacement badges/decals and also look at some different colour combinations if the case is very badly discoloured and you'd like something a bit different/personal.
Changes made in this video:
[1] Heatsink on the 6560 VIC to spread its heat better
[2] Replace the 4KByte 2332 character ROM with an 8KByte 27C64 containing the VIC-20 and C64 fonts
[3] Replace the 8KByte 2364 kernel ROM with a switchable 16KByte 27C128 containing the NTSC kernel and (a licensed copy of) JiffyDOS
Coming in Part 4:
[1] Replace the 6502 CPU and 6522 VIAs with modern CMOS variants (bought new from Mouser)
[2] Implement a 9VDC input socket to bypass the rectifier (more power/heat savings)
[3] Maybe replace the BASIC ROM (more power/heat savings)
[4] Maybe look at improvements to the video output (or maybe in Part 5?)
Replacement case badges, including custom requests ... doh, no longer selling on Etsy ๐ฅน
https://www.etsy.com/au/shop/lukparts
However, an alternative source of high quality replacement badges - I've not tried him myself but he is highly recommended:
https://retro8bitshop.com/retrostore/badgeman/
Converter board for kernel ROM:
https://github.com/SukkoPera/Open2327RomAdapter
Sven's converter board for the character ROM:
https://github.com/svenpetersen1965/VIC-20_Character_ROM_Adapter
JiffyDOS:
http://www.go4retro.com/products/jiffydos/
Comparing normal loading vs. JiffyDOS:
https://youtu.be/nMLDUlF3dcU
Modern regulators:
https://www.ezsbc.com/