Retro Challenge - 2015/07 - Day 31

More Wiring Up

Completed the various wiring bits that needed doing. Made a power board that connects the incoming power connections to the main circuits via a removable umbilical that can be removed to disassemble the machine.

Cut the circuit boards down to size with the Dremel and tied the cabling together with tape.

Glued the main power board into place.

Added in the secondary power board that provides the switching between internal power and external mains.

Connecting wires between the power boards.

VGA Output

Connected the VGA wiring harness to the internal resistors, found the ones I needed from the maintenance manual that has a full circuit diagram of the machine.

Testing the output. Works ok but there seems to be a weird problem with colours not working, the output is correct but everything on the screen seems to be white.

Power Switch

Fitted the power switch that allows me to turn on battery power.

Finished Machine

The machine pretty much completed.

Switched to battery powered mode. Screen is showing MOS command prompt.

Look no wires :)

Outstanding Bits

There are a few issues that I still need to resolve.

Firstly the VGA seems to not be displaying colour, not sure if it was just me or if there is an issue. Need to check the actual output on a real monitor to ensure that we are getting colours.

Battery needs to be fixed internally in some kind of holder so that it doesn't get hot from any chips on the board.

The original brown front has been removed, I want to get a new custom vinyl printed that will also cover the screen boarder. Didn't manage to get time to design and get it printed.

GoSDC is working ok but I'm not sure what I'm doing wrong as the patched ADFS and DFS won't seem to load.
Not getting any errors from it but the filing systems I've asked it to load don't appear. Going to try it in the normal master and see if its an issue with the Compact.

All Good Thing Must Come To An End

Well that's me done for this RetroChallenge. Looking forward to reading everyone else's blogs. See you all in the 01/Winter :)

Retro Challenge - 2015/07 - Day 3

Battery & Charging Circuit

Well some parts I'd ordered arrived so I decided to solder them together to test out the chargeable battery.

Here is the current charging circuit connected to the mains and the Gonbez. I can remove the power from the main socket and the battery takes over.

This should hopefully provide a 5v input which will charge the LiPo battery when the unit is plugged in. I intend to wire a switch in between the charging board and the step-up board so that I can turn off the machine without stopping it charging.

The charge circuit takes 5v in but the battery is 3.7v. To be able to supply the 5v needed for all the internal boards I am using a step-up board that will take the 3.7v to 5v. I have tried it with the Gonbez board and it runs this ok.

Mini TV Screen

I have a very small TV screen which I bought. The next step is to wire up the screen check it works with the output from the BBC.

Retro Challenge - 2015/07

The Problem...

I currently have a BBC Master setup on the desk in my office. The problem is that its not very portable, if I want to take it anywhere it requires a large CRT monitor or my recently acquired Gonbes VGA convertor board, a modern monitor and a set of power supplies.

You then also need to take either a disc drive or the DataCentre to give me access to disc images so that I can actually do anything.


I have a spare BBC Master Compact which I intend to make much more portable.

To do this I intend to add the following to the machine...

1) As the original BBC Master Compact uses a large desk unit to house the disk drives I need an internal method of storing software to run on the machine.

So I bought a GoSDC board which adds an SD card allowing me to store all of the software I need to use. The device plugs into a spare ROM socket internally in the machine.

John Kortink who designed the board was kind enough to supply one without the headers as he thinks the Compact may not have enough room inside with them attached. If this is the case I will need to wire a set of switched to the board to enable and disable it for updating the firmware.

2) So that I can run the machine away from any kind of power supply I want to add an internal rechargable battery.
Probably a lithium one with a charging circuit to provide a few hours of usage without needing a power supply. Obviously when the power is supplied it should cut off and charge the battery instead.

As part of this I will add in a power switch so that the machine can be easily turned off and will allow for charging without the machine being powered up.

3) To provide a VGA output I will fit the Gonbes board internally and provide a VGA socket on the back for connecting an external monitor.

This will require the power to the board and the TTL RGB output from the BBC to be wired to the board,

4) So that I can use the machine while on battery and without a VGA monitor or TTL RGB one I intend to provide a small screen built into the machine. This will probably be a 3-5 inch screen added to the top area of the case. Depending on the screen type this will either be wired to the composite out or to the second port on the Gonbes board.

This should be a mirror of what is output to the VGA / TTL RGB. I might put a switch in to be able to turn it off as it will display even when connected to an external monitor. If I have time it would be cool if when the external monitor is connected it displayed a cool logo.