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Old 14th Jun 2019, 8:14 pm   #186
Slothie
Pentode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 144
Default Re: MK14 schematic revisions

Due to technical issues (OK, mistakes!) the bottom connector P4 is numbered the other way round - so the address lines are on the right (near the vertical resistors) and the VCC/XOUT/NRDS/NWDS signals are to the left, underl the power/ground connections. I'm not sure if the VCC is going to be all that useful given that the regulator glows in the dark as it is, but it might be useful for something.

As for decoupling capacitors - I have been thinking seriously about this and I am glad that you also think it would be a good idea to make room for at least a few more where they can be fitted. The design as originally given works but I think that it can't do any harm to place holes for them even if I don't choose to populate (all) I'm not convinced my layout of the power rails is particularly optimal and I'm using a modern switching power wall wart which typically generate a lot of high frequency noise of its own. With the additional chip and a few other changes I have made its not like its going to be mistaken for an original unit anyway! Looking at the power and signals on an oscilloscope reveals a lot of noise, which might explain the occasional reset problems I had noted.
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