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MPU3 RAM board mod.


Late mod 6 MPU3 boards were fitted with a RAM daughter board which took a single 6116 RAM chip rather than two 5114 chips.


The growing problem of sourcing 5114 RAM for MPU3 boards has meant going further and further a field in order to buy replacement RAM chips. I bought the last lot from the USA.


Again, a solution from Andrew Finn has meant that a neat little RAM board can be added to your MPU3 which will take the single 6116 which is readily available for around £2.50.


Very neat and very small, the pictures show the board with a 6116 fitted.


Credit where credit is due, Andy came up with the mod very quickly. I ordered mine pre-soldered with a socket for the 6116 so they are ready to be installed and used. The RAM board plugs into the 2 existing 5114 sockets.


This will work in almost all MPU3 boards, the exception being some MOD6 boards which used slightly different RAM with different pin-outs.

MPU3 and 4 coincell modification


Finally a solution from Andrew Finn which will prevent the green Varta batteries from leaking and destroying your MPU.


Very neat complete with blocking diode, this non-charging coincell mod will fit directly into the existing holes on an MPU4 or MPU4 board or any MPU that originally took a 2.4v Varta mempak battery. Estimated to last around the same as your PC CMOS battery. (several years at least)


Very slick and installed in the same time as it would take to install a conventional battery and costing not much more. It’s really a no brainer and I’ll be installing it on all my MPU4 boards and MPU3’s.

Observation:  The cost of the pre-soldered RAM board even with a 6116 fitted it less than it would cost to buy two 5114 RAM chips, that’s assuming you know where to buy them in the first place?


recommended modification


Observation:  The cost of the coincell modification is slightly higher than the cost of a replacement Varta mempak battery, however, these coincells are extremely unlikely to do any damage even when they expire.


For added peace of mind the difference in cost is well worth the extra few quid.


recommended modification