PROJECT TESTED AND WORKING IN CBM 8050 disk drive, CBM 8250 disk drive, Commodore 1541 disk drive, C=64 and VIC-20 computers.

There are tons of these boards here, but almost all of them were made for using more than a kind of (E)EPROM, with jumpers, resistors, etc.

IF YOU HAVE A BROKEN VIC-20, C=64, 1541, CBM 8050, CBM 8250, ETC. AND YOU JUST NEED A STRAIGHT AND EASY WAY TO REPLACE THE ROM WITH AN EQUIVALENT EPROM, THIS IS FOR YOU. It replaces BASIC and KERNAL ROMs for VIC-20 and C=64 and the other ROMs in many Commodore disk drives.

This simple adapter allows you to replace the 2364 ROMs with a 27(c)64 EPROM or 28(c)64 EEPROM in your VIC-20, Commodore 64, 1541 drive etc. and also in the CBM 8050, CBM 8250, etc. drives that need an inverted /CS signal.

Beware: it can't be used to replace the VIC and C=64 Char ROM! If you need to replace the Characters ROM for VIC-20 and C=64, here you have the links to the right projects:

Adapter for C=64 Characters ROM: https://www.pcbway.com/project/shareproject/Easiest_Commodore_VIC_20_Char_ROM_adapter_cb1f22b2.html (please don't care abouth the link tells VIC-20, it's the right link!)

Adapter for VIC-20 Characters ROM: https://www.pcbway.com/project/shareproject/Easiest_Commodore_VIC_20_Char_ROM_adapter_using_2732_EPROM_064be19d.html

For the CBM 8050 / 8250 etc. you need to solder an smd 74LS04 chip on the board, before to solder the EPROM socket.

Otherwise, if you will use in a VIC-20, C=64, 1541 drive etc. the 74LS04 chip is not required. In this case you only need to connect the pads together the pin #8 and #9 of the IC with a blob of solder os a zero ohm smd jumper.

Build instructions:

Add a jumper or the 74LS04 chip, depending on the equipment where you will replace the ROM.

The IC is required only for CBM 8050, 8250, etc. disk drives

PICTURE ABOVE: Setup for most cases, like VIC-20 C=64, 1541, etc.

PICTURE ABOVE: 74LS04 for use in CBM drives series that require an inverted /CS signal (8050, 8250, etc.)

Suggestion: use a 24 pin socket to keep the two single-row connectors perfectly aligned before to solder them

Ok, first solder step done. Now you can remove the 24 pin socket and take the 28 pin socket....

The adapter finished. I strongly recommend to use high precision sockets.

NOTE: if you have the 74LS04 in place, you will need to cut the middle spacer of the 28 pin socket, or there will be no way to put it in place because it will touch the IC.

Here an example of the adapter installed into a 1541 that was modded for using with a CBM PET by the IEEE488 protocol (sorry for the bad picture....)