ET-3400 ROM adapter

From: Doug Yowza <yowza_at_yowza.com>
Date: Mon Aug 10 22:29:34 1998

In the last episode of the continuing saga of my little almost-complete
ET-3400, you might remember that I found the LEDs for it, but not the ROM
chip. Of course, it turns out the ROM chip is pure unobtanium: a special
mask-programmed MCM6830A. Luckily, I found that Heathkit was still in
business, and still supported the ET-3400, so I ordered a ROM chip from
them.

They send me a 2716. Hmm, it's not pin-compatible, so no big surprise
that it doesn't work. So, I called them up. "Oh, you need an adapter
board for that old ET-3400, but we stopped making those things 15 years
ago." It turns out that one of the techs there has the last adaptor board
sitting in his desk drawer. Now the adapter board is mine!

But it needs a buffer chip. The tech says "I think it needs a 74LS174".
But that's not a buffer chip, and it's got the wrong number of pins (16
instead of the 14 the socket has).

I'm guessing it really needs something like a '242 or '243. Is there any
way to know for sure without guessing? Am I going to blow anything up by
trying the two chips above? Any other guesses?

-- Doug
Received on Mon Aug 10 1998 - 22:29:34 BST