deskthority

Got this keyboard a few months ago and today I decided to get it working.

Unfortunately, I've bumped into some problems. It seems this keyboard was supposed to be powered at 11V. I've identified the controller (which runs at 5V) and the power regulator so I should be able to bypass that and feed 5V directly.

This is the controller : http://html.alldatasheet.com/html-pdf/1 ... 749HC.html

This is the power regulator : http://html.alldatasheet.com/html-pdf/6 ... 805VP.html

This is a schematic I found for another Ampex : http://www.kbdbabel.org/conn/kbd_connector_ampex210.png

Using a multimeter I checked the connections and I have 2 GND connections, a VCC and one unknown.

Can anyone help me figure out the next steps ? Why do I have 2 GND ? Is it a serial connection on 1 wire or there's a short and it's Data & Clock ?

Here are some pics with shitty paint :

Nice find. I have been looking for one of those, but they are tough to find in the US. I am pretty sure they use a serial data stream that transmits ASCII character codes. Do you have an oscilloscope that you could use to look at the data? If I remember correctly, they have a switch on the back where the XT-AT switch normally is that is labeled 270-280-232. I always assumed this was some sort of protocol switch based on the model numbers as there was an Ampex 270, 280 and 232. Given the 7805 regulator, I assume the input voltage is > 5V so the data line may operate at the same voltage, which is common for RS-232. It appears that there is a totem-pole transistor setup on the board, which would be used to drive the data line....so it all seems to fall in place for a single line serial connection at a voltage > 5V.

Considering the voltage problems and serial connection should I just handwire everything with a teensy ?

You will have to be careful with the voltage. If the data line is at the input voltage level, it will be too much for the teensy. You will need a level converter if you are going to connect using the pins that the original cable connects to.