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You don't really need a dual voltage power supply.
5V at 3A is more than enough for most MPUs you will be testing.
I use a small 5V 3A plug pack type switching supply worth about $5 - your concept is overkill unless you intend testing/repairing professionally?
Quoted from DrChrys:I am only doing it as a hobby but I like to be prepared. I used some connectors and wires and measure the amperage in game. In case someone needs the values, for the 5V circuit I got 500 mA (0.5 A) and for the 12 V circuit I got 4.1 mA.
Your measurements are next to useless useless we know a LOT more detail:
What board are we talking about?
What else was connected to it when measured?
What parts have been replaced on this measured board (some compatible parts that might have been used in a repair draw more current than others even at idle)?
Many more things.................
Quoted from phishrace:The first sentence in the original post says they're working on a WPC CPU 89. I'm going to go out on a limb and guess that measurements were made at connector J210 (mentioned above) on the CPU board.
Sure, I agree with your assumption but there are still too many unanswered questions.
Is this an original PCB with all original parts or have some chips been replaced? If some HCT ICs have been replaced with LS types or vice versa, this would change the current draw overall. Same issue if the RAM has been replaced with NVRAM or a different brand RAM.
It's nice to have a ballpark figure but the trouble with that is you will then have some people chasing a 'magical' figure (in this case) of 500ma when their board might draw 550ma or even 480ma and be perfectly normal.
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