Task: Erase a 40-Pin AM27C400 Programmable EPROM With Ultraviolet Light
Needed: AM27C400 EPROM, UV light source, TL866 universal programmer
Time: 30-60 minutes
Introduction
I have previously posted about burning 40-pin AM27C400 EPROM chips for upgrading the ROM of an Amiga 1200. Unfortunately, several of my EPROMs were not fully blank and failed on the write operation. The good news is that you can erase these with ultraviolet light. My first attempt was to try a cheap Chinese-made UV light box I got on Amazon for about $30. The unit arrived defective and was not emitting any light. Others have also received nonworking units of this type. I next tried a 25W UV light bulb like this one that worked great!
Instructions
You will first need some AM27C400 EPROMs that need to be erased. I will assume you have one or more to complete this project. Here is the source of the EPROMs I used on eBay if you need to buy some.
Second, you will need a TL866 universal programmer to check the chips once they are erased. I have previously posted about these devices.
Third, you will need a 27C322/160/800/400 EPROM adapter. I previously posted about this important device.
Fourth, you will need a good UV light source that is strong enough (e.g. UVC for germicidal use) to erase the EPROMs in a reasonable amount of time (e.g. 20-30 mins). I bought this one on Amazon.
Fifth, you will need a lamp for the 25W bulb and safe place to use it to erase the chips so that the UV light does not hurt you, your pets, or physical items.
Once you have all the components, you are ready to erase come chips. You will see in the image about that I placed my lamp in a box to expose the chips. I closed up the cardboard box and covered it with a towel to prevent any rays from escaping holes. I exposed the chips for about 30 minutes which worked fine.
Once finished, you can check the erasing with the TL866 and adapter. Below is the before and after results for my chips. Remember to uncheck the pin detect and check ID options in the lower left of the XGPro screen.
There is also an option run a blank check from the menu.
Comments
This was easy and fast assuming you have the right UV light source. These UV bulbs from Amazon worked really well in my hands. I am sure there are other solutions. However, I would steer clear of the cheap Chinese-made UV light boxes. The reviews are terrible.