Author Topic: How many amps does the 12V line *really* need?  (Read 1030 times)

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Offline llopis

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I read this comment in the Wiki:
Quote
Note that the power supply for the Spectrum +2A model gives the right voltages, but only provides 12V at 0.2A, which may not be quite enough for the 6128.
Unfortunately the only power supply I have handy is a Spectrum +2 one that provides 200mA. But the comment intrigued me with the "may not be quite enough" part. Does anyone know how much it really needs?


I'm probably going to go ahead and create an adaptor and find out, but it would be good to know if I'm wasting my time and I should just go the route of getting an external HDD power supply (Spectrum +3 power supplies seem to be somewhat rare these days).

Offline rpalmer

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Re: How many amps does the 12V line *really* need?
« Reply #1 on: 14:11, 14 June 18 »
llopis,

I think the CPC 6128 needs at least 1A for the floppy as it uses 12V 1A for the motor/head drive.

rpalmer

Offline Bryce

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Re: How many amps does the 12V line *really* need?
« Reply #2 on: 14:52, 14 June 18 »
I did real life testing of the 12V rail when I was designing the 5VCPC device. The current varies depending on the type and age of the floppy drive. The very worst case I found had spikes of up to 300mA, but the average normal consumption is around 200mA.


I use a Spectrum +3 PSU to power my CPCs and haven't had an issue so far.


Bryce.

Offline llopis

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Re: How many amps does the 12V line *really* need?
« Reply #3 on: 16:02, 14 June 18 »
I did real life testing of the 12V rail when I was designing the 5VCPC device. The current varies depending on the type and age of the floppy drive. The very worst case I found had spikes of up to 300mA, but the average normal consumption is around 200mA.
Hmm... that probably means my +2 PSU is not going to be enough sometimes. Unfortunately I can't find any Spectrum +3 PSUs around.


Any thoughts about using a PS intended for disk drive connectors like this?
https://www.ebay.co.uk/itm/SATA-PATA-IDE-to-USB-2-0-Adapter-Converter-Cable-For-2-5-3-5-Inch-Hard-Drive-Set/292115770402


They output +5V and +12V with plenty of current. Would they be a good alternative?

Offline Bryce

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Re: How many amps does the 12V line *really* need?
« Reply #4 on: 16:16, 14 June 18 »
They claim to be able to supply plenty of current, but I've gone through a few of these already and they all died just trying to supply the voltage to a single HDD.

If you are interested, I may still have a 5VCPC left over, need to check:  http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/5vcpc/msg139702/#msg139702

Bryce.

Offline llopis

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Re: How many amps does the 12V line *really* need?
« Reply #5 on: 18:05, 14 June 18 »
If you are interested, I may still have a 5VCPC left over, need to check:  http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/5vcpc/msg139702/#msg139702
I was just reading about that project earlier today :-) Thanks, but for now I'd rather find the correct power supply. I'm going to be dealing with multiple CPCs, so I'd rather one power supply that works for all of them.