Ashtead's Journal: Hardware notes, updates

So I've dusted off the 468 scope again, the one I bought for 40 kroner or so, some years ago and had another investigation of its malfunction. It looks like there is something wrong with the ROMs as it doesn't get very far from start-up to halt. (pins 29 and 33 on the 8085 going both LOW). I've managed to find some memory dumps of these on the Internet, so I'll try burning 2764s and connecting these, then see what happens next.

Then there is the other acquisition, the HP3330B synthesizer. This thing works fine, so I've had no need to open up the box. But there's this interesting "remote control" connector on the back, and I have been able to procure the complete manual for this unit. Turns out this "remote control" interface includes a listen-only variant of IEEE-488, minus the cable-interface, so I could either construct that (just putting in some buffer-circuits) or make another parallell-interface, maybe via I2C or similar to a Picotux, so that I can put the synthesizer directly onto a local network. The signals are all 5V TTL-level ones, so there is just a matter of sticking some 74LS05 open collector inverters between the device and two PCF8574s, making both sides happy about the electrical loading. That was the easy part, figuring out this.

The slightly harder part is to verify which way is up and down, and which letters and numbers are used, although looking at omitted connections and seeing the correspondning non-connected fingers on the card edge sticking out, makes this an easily solved puzzle. There is basically 2 by 18 positions, and in the manual one side is numbered and the other side is marked by letters.

Running the synthesizer in sweep mode should make it generate pulses on the sweep-address outputs, so it should be reasonably easy to figure out where these are, and by elimination, which pins are the IEEE-488 set where the thing can be controlled.

The less-than-easy part has proven to be obtaining a 4 mm pitch card-edge connector. All the current places I've seen have only fancy 1.27mm and suchlike tiny-pitch connectors available now; the old and large 4mm pitch seems to be unobtanium... Even 2.54 mm, the old familiar standard, is getting harder to locate. And I haven't seen any 2mm pitch ones either, at least that would be somewhat compatible with the 4mm pitch connector, just removing every other pin, or maybe it can be aligned so that two pins match each finger. I will have to finagle something here... perhaps take one of the 2.54mm pitch connectors that I do have lying around, then pull out every other pin and cutting it up into slices and mount these on a circuit board, so that the spacing becomes the requisite 4mm.

I do not want to solder anything onto the card-edge and damage it.