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+--- Thread: PC85 coreboard regulator current draw? (/thread-427.html)
PC85 coreboard regulator current draw? - CheshireNoir - 03-02-2022
Hey folks, does anyone have an accurate measurement of how many amps are needed on the 5v rail on the PC85 core board?
I have some 500mA TRACO 7805 drop in replacements, but if it's going to need a full amp, I'll need to get something beefier.
This is to replace IC37, the regulator.
If no one has an answer, I'll assume the worst and get the higher rated regulators. They're just not cheap :-D
Chesh
RE: PC85 coreboard regulator current draw? - ChickenMan - 03-02-2022
Not sure on the PC85 but I've used what was listed as 5v 3 watt units in a Premium 128k (my Overdrive) which work well. See pics etc My Microbee 128k Overdrive upgrade (microbeetechnology.com.au).
RE: PC85 coreboard regulator current draw? - someone - 03-02-2022
Normally populated SRAM coreboards don't draw much power nor do their voltage regulators generate much heat.
Is there any particular reason for using expensive switching voltage regulators?
The Hitachi HM6116P and LP SRAMs were a fantastic development using far less power and being considerably quieter than the previous generation 2114 1K x 4 SRAMs.
The TCT 16K RAM card used 4 x 7805 TO-220 voltage regulators, the subsequent AT16K used a single 1.5A TO-3 cased regulator.
RE: PC85 coreboard regulator current draw? - CheshireNoir - 03-02-2022
(03-02-2022, 05:44 PM)someone Wrote: Normally populated SRAM coreboards don't draw much power nor do their voltage regulators generate much heat.Thanks someone.
Is there any particular reason for using expensive switching voltage regulators?
The Hitachi HM6116P and LP SRAMs were a fantastic development using far less power and being considerably quieter than the previous generation 2114 1K x 4 SRAMs.
The TCT 16K RAM card used 4 x 7805 TO-220 voltage regulators, the subsequent AT16K used a single 1.5A TO-3 cased regulator.
I was mostly worried about heat :-)
It certainly gets hot to touch without a generous heatsink.
If it was pulling under half an amp I actually have the regulators left over from another project.
Chesh
RE: PC85 coreboard regulator current draw? - someone - 03-02-2022
(03-02-2022, 09:02 PM)CheshireNoir Wrote:(03-02-2022, 05:44 PM)someone Wrote: Normally populated SRAM coreboards don't draw much power nor do their voltage regulators generate much heat.Thanks someone.
Is there any particular reason for using expensive switching voltage regulators?
The Hitachi HM6116P and LP SRAMs were a fantastic development using far less power and being considerably quieter than the previous generation 2114 1K x 4 SRAMs.
The TCT 16K RAM card used 4 x 7805 TO-220 voltage regulators, the subsequent AT16K used a single 1.5A TO-3 cased regulator.
I was mostly worried about heat :-)
It certainly gets hot to touch without a generous heatsink.
If it was pulling under half an amp I actually have the regulators left over from another project.
Chesh
What is the measured input voltage into your microbee? Ideally you should tune your microbee to run from 8.5-9.5 V (for DC IN models).
If you're not using the serial ports then you can replace the voltage regulators with LDO (Low Drop Out) versions and run them even lower.
The old S100 systems that the microbee was derived ran from 8VDC (unregulated) with standard 7805 regulators. The reason why microbees ran originally with 12VAC then 10VDC was to generate sufficient serial output signal voltages.
Be careful because if you run some microbees at +12VDC the aged tag tantalum capacitors (even rated at +16V) have a tendency to explode and launch nasty fireballs.
The lower the input voltage the less you'll stress the power supply components.
Just note that you may also need to tune the POJ voltage sensing circuit to match the adjusted input voltage.