How many amps for old style 12v M2?

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ketil
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How many amps for old style 12v M2?

Post by ketil » Sun Apr 25, 2021 5:59 pm

It seems I'm on an unfortunate streak with my M2. As I was replacing the busted fan and my botched Y motor, the power supply unit died. No idea why, I disconnected it when I was doing any work on electronics, but it's clearly dead. Didn't occur to me for a while that this was the problem, so I had to do some debugging before I understood juat why things weren't working.

The old M2 had 2 PSUs, one for the printer itself, and a separate one for the hotbed. It was the printer PSU that died, which was rated at 19V 6amps. I dug around in some old drawers and found an unused laptop PSU rated at 19v 4amps, which I proceeded to connect to the printer. So far I've run several prints without a hitch, so it appears that 4 amps is sufficient.

Is there any reason to think that I need to get a new PSU rated for more amps, or should I just keep at it with this one that clearly works anyway?

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ednisley
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Re: How many amps for old style 12v M2?

Post by ednisley » Mon Apr 26, 2021 1:54 pm

ketil wrote:
Sun Apr 25, 2021 5:59 pm
found an unused laptop PSU rated at 19v 4amps
First rule of fixing things: ya gotta have stuff! [grin]
it appears that 4 amps is sufficient
Power supplies these days know how to protect themselves from overloads, so when it seems to be perfectly happy, you know it is!

Because you've depleted your parts stockpile by one unit, getting a slightly huskier laptop-ish power supply (anything from 19 through 24 V will be fine) from eBay seems like a good idea. Ya never know when you'll need a power supply.

While you're thinking of it, re-check the other supply, because that old 12 V heater requires far too much current and tends to overheat / char the connector shell at the PCB.

ketil
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Joined: Wed Apr 09, 2014 9:58 pm

Re: How many amps for old style 12v M2?

Post by ketil » Mon Apr 26, 2021 6:01 pm

Thanks for the feedback Ed! And for the fair warning regarding the heater PSU. After melting 3 connectors I've actually given up on the heatbed, so now I almost exclusively print PLA on a bed coated with wood glue. The 12v heater took ages to heat up anyway, and finally caused enough trouble for me to opt for this route instead.

But I think I get your point that I could get a slightly beefier 24v PSU now, to have as a backup but to also be prepared for a 24v upgrade one day. Nice plan.

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ednisley
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Re: How many amps for old style 12v M2?

Post by ednisley » Tue Apr 27, 2021 1:02 pm

ketil wrote:
Mon Apr 26, 2021 6:01 pm
be prepared for a 24v upgrade
I don't know how much current the stock 24 V heater draws, but the total will be near the upper limit for a laptop supply.

If you don't have small children underfoot, a real power supply might make more sense than a laptop supply. The minimal protection over the AC terminals isn't suitable for casual use, but the current limits are much higher, perhaps with bonus fan noise.

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