I have been selling adapters to replace the MPS-6540 ROMs in the Commodore PET-2001 since 2009, but until now, there has not been a solution for the equally scarce MPS-6550 RAM chips. This product finally solves this problem once and for all by making a simple way to replace a 6550 RAM chip with a common 2114 RAM chip! These adapters feature:
-Fully functional pin-compatible replacement for the MPS-6550.
–Batten and Allen PCB edge pins. These pins exactly replicate the shape of a proper DIP pin and thus will work reliably in any DIP socket without damage. No kind of through-hole pin can claim this!
-A gold-plated machined DIP socket to hold the 2114 RAM
-A light weight and low-profile design that fits easily in the PET and is unlikely to come loose from the socket if the PET is jarred.
-All visible components are vintage-style through-hole parts so the adapter will not look out of place in a 1977 PET.
You will receive:
– One adapter capable of replacing a single MOS Technologies MPS6550 ROM chip.
– The needed 2114 RAM chip.
– A lifetime guarantee on the adapter. If the adapter does not work in your computer I will work with you until the problem is solved. If the adapter ever fails, just mail it back to me for a free repair.
PLEASE NOTE: These adapters will ONLY work to replace a chip with a part number starting with 6550. They will NOT replace RAM types used in Commodore computers other than the original Commodore PET 2001. If you don’t know if you have a bad RAM chip, or if you don’t know which one is bad, you should read my guide to troubleshooting the Commodore PET 2001 here.
The one disadvantage of these adapters is that they are about 0.3″ taller than the original 6550 chip and thus may not be mechanically compatible with all 3rd party expansion boards. Please make the appropriate measurements before ordering.
Download the schematic and PCB layout for this product here. Note that these files are available for PERSONAL, NON-COMMERCIAL USE ONLY. In short, you are welcome to use them to build this product yourself, but you must contact me to work out a commission if you wish to sell anything derived from them. This product was designed in ExpressPCB so you will need to download a copy of that software from expresspcb.com before you can view the files.
If you have any bad or missing any 6550 chips in your PET, this is the solution you’re looking for. I’ve seen other products that replace all of the RAM with modern components, but these adapters allow you to replace only what you must, and keep your PET as close to its vintage configuration as possible. The pins are flat like real 6550 chips and will not stretch out or stress the sockets. They are perfect. Thank you for bringing my PET back to life!