exxos's Atari, Amiga & retro forum

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She lives!!


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Long live the Frankenscreen

Hmmmm M'Kay....

RAMdomizer soldered in:)

Next to find some DRAM to test it with :)

All that was a fail... Short-circuits across the power rails somewhere :roll:

So started sucking up the VCC pins as it is the only place which can be shorted to GND... and did not find anything wrong :roll:

Loaded up the PCB file, ran DRC.. no problems found..

Tried a blank new PCB and the short is on the PCB itself somewhere :roll: :headbang:

Is it just me, or do you have a track running right into those holes?

Edit: I guess it does steer around them. Looks mighty close. :)

derkom wrote: 27 Apr 2020 16:03 Is it just me, or do you have a track running right into those holes?

Edit: I guess it does steer around them. Looks mighty close. :)

They do steer around the holes... The socket holes look like they might be Via's under the microscope, but I cannot get continuity across any of them...

The board alignment top and bottom looks pretty spot on.. :shrug:


I might just hook it up to my big power supply and crank up the amps until something catches fire :twisted: :twisted:

Right, here is a exxos lesson in fault finding a power rail short..


First up a proper low resistance meter..



Basically what we do is check the resistance across various capacitors around the board and look at the resistances...


I started at the bottom right corner of the board working my way up with and to the left taking note of the resistance...Which is 84.2mR..


Moving upwards on the board you can notice the resistance gets slower, so we are getting closer to the short! Now 35.9mR!



Now I can only move to the left...So moving along one by one the resistance got lower and lower until there was nowhere else to go...


This is the lowest resistance point on the whole board on the power rail at 11.3mR.

So checking what capacitor that is on the PCB files...


D'oh! :headbang:

It looks like when I moved the capacitors about, to the right, I must have missed that one for some reason it should have been further to the right :roll:

Bodge wire time...