Page 1 of 1

Bad power supply. I think.

Posted: December 15th, 2019, 11:52 am
by Stevefury
I've used my Makerbot Mini quite a lot since new in 2015, printing almost every day.
I was printing a battery mount yesterday when it suddenly stop mid-print.
Usually, when an error occurs the print bed will be driven down a couple inches and the hot end/gantry goes "home".
The suspected trouble would be indicated in a warning box on the Makerbot software.

This time it just stopped amid print, hot end stuck on the print with a solid red starting button (trouble).

I reboot the Makerbot Mini.
Normally, the printer boots with the button blue for about a minute then it plays a short tune and turns on a red light to
illuminate the build space.
This time the button is blue like normal but never plays the tune, never goes ready.
The PC does not recognize anything is plugged into the USB port.

I figured out how to get to the motherboard and found +12, +5 and +3.1 volt test points.
I powered it up and found +12 but no +5 or +3.1v on the test points.
I checked at the big power plug from the power supply which has two clusters of thick red and black wires and two
smaller gauge yellow and gray wires.
I found one red wire had +5 but that is the only power on the entire connector.

I connected a regulated +5 3A "wall wart" to chassis GND and the (+) to one of the dead red wire clusters and the board
came alive with lit LEDs and the PC recognized the USB connection. After about a minute it gave the usual boot-up tune and
the Makerbot software indicated ready to print.

I tried to print but it immediately went to error, "Hot end short".

I did some research and the OEM power supply delivers 13 amps (wow!) for the +5 supply and I am putting a comparably feeble 3A
which I suspect is causing the hot end short error. I switched smart extruders and it made no difference.

I figured out how to get the power supply out which necessitated disassembling 90% of the printer. What an utterly stupid design
when you need to get the power supply out. Absolutely incompetent engineering IMHO.

I found a used but guaranteed good PS on eBay for about $40 with shipping but I wanted your suggestion first.
I am satisfied with the testing above that the trouble is almost certainly a bad power supply but can't be sure until I get a good
replacement. If I get the said-good used/new power supply and the printer doesn't boot then I'll be wondering if the mother board
is bad or maybe I got a bad replacement power supply.

I've been looking around Amazon (etc) and they are selling quite a few printers for under $400 which I am considering.
Kinda torn between gambling a few bucks with repairing my Makerbot or replacing it with a low cost one with a bigger
build volume.

Up to this point my Makerbot has been extremely reliable and great but I'm not sure about the reliability of those cheaper
units. I am spoiled by clicking "print" and not having to mess with the printer at all, to just get the printed item.

What would you do?
-Thanks

Re: Bad power supply. I think.

Posted: December 15th, 2019, 11:59 am
by Stevefury
Additionally,
Now that I have the OEM PS out of the printer, I can turn it on and observe its cooling fan remains off. I have the +5 on one red wire, that's all. I'm not sure if it needs a signal on one of its other wires (yellow or gray) so I experimented by applying the +5 line to both the yellow and gray. Nothing happened.

So...
I applied a GND to the yellow and gray. Still nothing happened. No output.
Seems dead to me.

Re: Bad power supply. I think.

Posted: December 16th, 2019, 2:18 am
by GrueMaster
You could probably convert a standard ATX PC powersupply to meet your needs. They're very inexpensive. Just make sure the power rating on 5v is what you need. Not sure exactly as I don't have any information on the Makerbot series (other than what I watched in the documentary on Netflix).

Re: Bad power supply. I think.

Posted: December 16th, 2019, 12:15 pm
by Stevefury
Thank you for the reply GrueMaster.
The power supply current output specifications are insane. 10 amps for +12 ... and... 13 amps for one +5 line.
I found a used supply at ebay for $40 with shipping.
The problem is, if it arrives and doesn't fix it then I have either received a bad used supply or problems with the mother board.
Used "good" (you know how ebay sellers can be) mother board is almost $100.

So I opted to abandon the Makerbot Mini and I've ordered a large volume printer, due to arrive in 6 days.

Re: Bad power supply. I think.

Posted: December 16th, 2019, 10:36 pm
by GrueMaster
Always good to have a spare. :P

Seriously, don't junk your old printer. $40 is really a low cost to get it working again (hopefully). Best case, you now have two printers for your ongoing projects. Worst case, lost time and a little money (cost of 2 spools of filament).