Check the listing for details. Heathkit ID-4001 CPU Adapter Board (IDA-4001-5). Listed at 50.00 USD. Data Professionals Main Page Heathkit ID-4001 CPU Adapter Board This PC board that will replace the Mostek 443-23 CPU in your old ID-4001 weather station. This is the same CPU Adapter that we have been selling for the past 10 years. Whether you need to replace a burned out CPU chip, or you just want to add new features to your old ID-4001, this CPU board will update your old ID-4001, allowing you to run it with your personal computer. Application software is available from "Thunderhead Technologies" and can be found on the web. To install the ID-4001 CPU replacement board (model IDA-4001-5), it will be necessary to remove the existing static RAM chip, one diode, and the existing crystal. These components will not be needed as the RAM function has been moved into the new CPU chip's memory. A 4.0 MHz crystal on the new board has replaced the existing crystal so that the frequency of the serial interface will be correct. All of these components should be carefully removed and set aside, should you wish to restore your ID-4001 back to its original state. Step by step instructions are included to remove the un-needed components and install the new CPU board. There are no irreversable modifications necessary to your ID-4001 weather station to use this part. This Processor includes Software as Firmware that belongs to Heath Company. International sales only through the eBay Global Shipping Program.