Acorn BBC Micro Model B

This BBC Micro Model B is has been extensively expanded.

BBC Micro Model B Issue 7 motherboard

As you can see from the photo, this particular model B has four extra LED's located on the bottom right of the keyboard fascia that are part of the RetroClinic DataCentre upgrade and it is connected to an Acorn 6502 Second Processor. The installation of a Disc and Econet interface on the motherboard together with an original Acorn Speech Synthesiser upgrade featuring the digitised voice of the BBC newsreader Kenneth Kendall complete the original upgrade potential of this BBC Micro.

In addition to the original upgrades, an ATPL Sidewise Sideways ROM board allows for the installation of the full complement of 15 ROMs that contain software from debuggers, printer drivers, filing systems, development support services to name just a few. 

This BBC Micro has a full complement of filing systems and supports ADFS, DFS, NFS, RetroClinic's RamFS and the CFS (Cassette Filing System).

Expansions

Expansions in this BBC Micro include:

The BBC Micro with the case opened showing all the expansions fitted

Beeb@30

On the 25th of March 2012, I took this BBC Micro to the Beeb@30 event which celebrated its 30th birthday. I used this BBC Micro to demonstrate the educational game Granny's Garden being run from the Acorn Archimedes A410/1 which was configured as an Econet server.

The BBC Micro running Granny's Garden from the Archimedes A410/1 Econet Server

Repair/Change History

PSU X2 Capacitors preemptively replaced in February 2011.

The sockets for the uPD7002 and MOS ROM socket were replaced with turned pin sockets and the central power spade connectors were replaced with flying connectors to allow for easier fitting of ATPL ROM board which was re-configured to its original factory state.

The 68B54 ADLC (Econet) and Acorn speech system chips have been added. The rest of the Econet interface was already fitted.

In March 2011 the machine started exhibiting random data on screen and ADFS file system corruption. The RAM buffer chip (IC14) 74LS245N along with a RAM chip (IC54) 4816AP-3 were replaced, the 74LS245N was replaced with a 54LS245J (military spec.) which has the same function but operates at a much greater temperature range to cope with the heat generated by the close by Video ULA (IC6). These changes did not fix the issue.

In April 2011, a small fan was fitted to keep the Video ULA cool which appeared to fix the problem. As a permanent fix, in early 2012, a VTi VC2069 Video ULA was fitted, removing the original VTi VC2023 chip and the Acorn modification that corrected an issue with the VC2023 which consisted of a flying lead connecting from pin 27 on the chip directly to a pin on header S26. The fix was completed by using a jumper to close the S26 header.

An 8 way DIL switch was added to the keyboard for the ease of setting the computers initial configuration settings.

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Acorn BBC Micro Manuals

Whilst the BBC Micro Service Manual is useful, RetroClinic produce a fully revised and updated Service Manual that covers the BBC Micro A/B,B+,Master and Master Compact which you can usually find for sale on ebay.

BBC Micro maintenance

Further information

The BBC Micro case was designed by Allen Boothroyd

Here are some links to further information and resources for the BBC Micro that may be of interest.

The 8 bit Acorn Webring