Small testrig for old DRAM 64kx4 Chips

I bought some old DRAM Chips from Ebay for the repair of an Amiga, so i looked for a way to test those chips to know if they are in working order before putting them in the board. There are some chip testers available on the market but i thought i could build one myself and maybe use it for testing other kinds of chips later by expanding on the code.

So here is my first try on a chip tester for TMS4464 / NEC 41464 and other compatible chips, those are 64k x 4 Bit organised, DIL18 case. I had some Teensy 3.2 and a 24 pin ZIF Socket in my storage, so i did a quick layout and etched a pcb. The schematic is quite simple, each connection of the ZIF Socket is connected to some header pins and the GPIOs of a Teensy 3.2 (since the Teensy is 5V tolerant), additionally i added 3 pins with GND, 5V and 3,3V to supply power to the chip with some jumper wires. Since i wanted it as versatile as possible you have to use the jumpers, but be carefull, the Ram chips have GND and VCC exchanged compared to 74xx TTL Chips. I recommend reading the datasheet of a chip before connecting it. Sadly i had no easy accessible GPIOs left to make the powersupply for the chip switchable in software, so i always have to power down the teensy to change chips, nobody is perfect. ūüôā

The first firmware can test the Databus, Adressbus and the complete Memory for errors.

And yes, that is a 7404 in the picture, i tried my pcb on a cheap chip first before trying on out of production drams.

Have fun! Please leave a comment if you build one yourself, have suggestions or improvements on the source.

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