A look at my “main” BBC model B and the upgrades that I’ve done to it, re-assembling the other model B, checking out the double floppy drive unit, and an update on what’s been happening with the Z80 build. Live streams on Twitch

More bits arrived so the Z80 boards are starting to fill up. Gave the BBC keys a bit of a clean, and with the soldering iron fixed, took the A501 apart to see what was going on inside, and a quick run down of things to come. ...

Quick lunch time stream looking at the latest PCB’s that arrived. Z80 Backplane ECB Disk controller EBC CPU card Live streams at Twitch

Trying to get the backplane connectors into the backplane board (they’re wire wrap connectors I think, so the pins seem slightly larger)… Seeing what IC sockets I have, checking some 74 series logic chips in the Minipro, first look at the “suspect” A501 from the Amiga, and salvaging a few bits from an old PSU. ...

Time to remove these old capacitors… …from this BBC model B power supply, circa 1983… …and put these new ones in their place. The expectation being that the smoke will stay in these ones (and so far it has).

My previous bench PSU (sitting on top of the new one) pissed me off one too many times… The new one comprises a couple of DP50V5A programmable PSU modules from eBay (eBay Link), a 48VDC PSU that I already had, that was already mounted in the case pictured. The case and 48VDC PSU had been used previously to power some other equipment and had a panel meter where the left LCD display is (hence the hole that’s slightly larger than the new PSU module), and a terminal strip where the right LCD display is. Maybe one day I’ll come across a nice new case for it – but today is not that day :-) ...

I came across some more “older” bits of computer hardware today. I hesitate to say “vintage” because they’re not /that/ old :-) The first, as the name says, is a Universal 68705 programmer made by Oztechnics Pty Ltd (which appear to have disappeared – the current Oztechnics is a domestic appliance repairer in Brisbane). I’ve had zero luck so far finding any information on this. The next is an M68HC05 emulator, which seems to be basically an in-circuit emulator for system development. I still need to track down some documentation for this one. ...

The PSU on the MEK6800D2 is a bit of an unknown quantity and built on veroboard. The whole assembly really isn’t in keeping with the rest of the system. I did find out that new LM309K’s go for near on $100 though! (the old PSU has one) So I’m taking the opportunity to build a new power supply. Still using a TO-3 style metal-can regulator, and a TO-3 SCR to crowbar the PSU in case of an overvoltage condition (sooner blow a fuse than blow up the 6800 system). I could have used modern packages, but I wanted to stay at least a little retro :-) ...

No idea if it works – haven’t even tried to power it up yet, and when I do, it’ll be from the current limited bench power supply as I have no idea if the power supply inside the box works or outputs the appropriate voltage. First mission is to track down the manuals and schematics and see if the empty IC sockets are going to be a problem, or if they’re just optional components for specific situations. ...