So I built a 3D printer kit and im using the recommenced power supply from open builds, 12V 30A power supply. Well the first one blew a thermistor I believe it is a ntc 5D-15. They sent me a new one and it happened again and it seemed to happen while the printer was unplugged and off, since I turned the printer off and when I went back to use it again I looked inside the power supply before turning it on and could see it was all cracked and apart. From what ive read all this thermistor does is create resistance when you first power it up. What could keep making it fail? Any help would be awesome thank you.
Hey! thank you for the welcome and reply. Its a prebuilt one, here's a link to it. I dont have a circuit schematic for it but ill see if I can find one. Unsure about a varistor too...
http://openbuildspartstore.com/12v-30a-power-supply/
http://openbuildspartstore.com/12v-30a-power-supply/
I used the term varistor as it is more likely to be one of those than a thermistor
show a sharp, clear and well lit pic of the insides of the PSU and show where the varistor came from
Dave
no, the supply can take 110 - 120 or 220 - 240 volts in without the need for switching ... as many SMPS units can these days
73's de Edd
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Sir USER1. . . . . .
I am seeing the tape covered terminals with the far right ends being the AC input
Then A.C. power comes in thru the now confirmed line surge thermistor and also passes thru the A.C. line
fuse. . . .Did it ever blow ? . . . .should have. . . .to have that line thermistor having been blown that SEVERELY.
Then there is that BLACK block X cap, being directly across the A.C. line.
Power passes up for some dual line filtering / cleaning thru that dual inductor.
The side SPDT slide switch then ascertains if the large pair of main filters need to
configured for voltage doubling mode for 120VAC use or straight thru filtering for 220VAC
use.
The large heatsinked rectifier block, nearby, provides their raw DC supply voltage.
It's meltdown might be the first suspicion.
Tell us what has been replaced so far
ASIDE:
" Line voltage is 123.4". . . . . . . . . . .WOW ! ! ! that is PERFECT line voltage. . . .coincidental ?
73's de Edd
I am seeing the tape covered terminals with the far right ends being the AC input
Then A.C. power comes in thru the now confirmed line surge thermistor and also passes thru the A.C. line
fuse. . . .Did it ever blow ? . . . .should have. . . .to have that line thermistor having been blown that SEVERELY.
Then there is that BLACK block X cap, being directly across the A.C. line.
Power passes up for some dual line filtering / cleaning thru that dual inductor.
The side SPDT slide switch then ascertains if the large pair of main filters need to
configured for voltage doubling mode for 120VAC use or straight thru filtering for 220VAC
use.
The large heatsinked rectifier block, nearby, provides their raw DC supply voltage.
It's meltdown might be the first suspicion.
Tell us what has been replaced so far
ASIDE:
" Line voltage is 123.4". . . . . . . . . . .WOW ! ! ! that is PERFECT line voltage. . . .coincidental ?
73's de Edd
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73's de Edd
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Sir USER1. . . . . .
I'm going to see what happens with a new one installed. (The same damn thing.)
WHAT . . . . so that you might further / then do some more SERIOUS damage to it ?
Got a DMM and familiarity with it, to do some preliminary tests ?
73's de Edd
I'm going to see what happens with a new one installed. (The same damn thing.)
WHAT . . . . so that you might further / then do some more SERIOUS damage to it ?
Got a DMM and familiarity with it, to do some preliminary tests ?
73's de Edd
Last edited by a moderator:
IF that is indeed the case, and IF the selector switch places the two big caps (assumed of equal capacitance) in parallel for a 240V supply or effectively in series for a 120V supply, then the mains inrush current when using a 120V supply would be much higher than designed for if the switch were inadvertently set for 240V. That could have blown the varistor.
73's de Edd
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Sir USER1 . . . . . . .
Basically you need to test across the 4 diodes in the Black Full Wave Bridge Rectifier which is clamped against the marked, but non existent Heat Sink 1 . . . .HS1..
That would require that the 4 corner Phillips lag screws be removed and then wiggle the board to see if the very end mounted power devices clamping screws also need removal.
Get access to the bottom foil paths and then I will fill you in on testing . . . . . .you are going to require bottom board access, anyhow, in order to replace the now damaged RT 1.
73's de Edd
Basically you need to test across the 4 diodes in the Black Full Wave Bridge Rectifier which is clamped against the marked, but non existent Heat Sink 1 . . . .HS1..
That would require that the 4 corner Phillips lag screws be removed and then wiggle the board to see if the very end mounted power devices clamping screws also need removal.
Get access to the bottom foil paths and then I will fill you in on testing . . . . . .you are going to require bottom board access, anyhow, in order to replace the now damaged RT 1.
73's de Edd
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73's de Edd
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Sires . . . . . . .
Clarification of . . . . . IF . . . .it is done . . . . . . as to . . . . HOW. . . .it is typically done :
73's de Edd
Clarification of . . . . . IF . . . .it is done . . . . . . as to . . . . HOW. . . .it is typically done :
73's de Edd
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73's de Edd
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Sir USER1 . . . . . . .
Here are the foil paths to component layout relationships on your units PCB.
I certainly would suspect the fuse, having been blown, if the unit below has any shorted internal diodes.
Your units Full Wave Bridge Rectifier is located halfway between the upper 115 / 230V selector switch and the lower pair of BLUE Y caps.
This fellow is testing the same cased unit as yours is having . . . . . . it's just being flipped 180 degrees hoz.
HEY I forgot to ask . . . . did you get any initial " Three Dee" printing done ?
Or did this units failure, stop you, just after the " Th. . . . . . . . . .".
The filament string heater and the units drive "moders" whiff up quite an amount of power !
BTW. . . . In case the info might be needed for your . . . or others . . .units in the future,
could you pass on the part number of the controller I.c. .
I can see that it's having too many pins for the common ua 384X series and it's feeding into
a pair of complementary transistors for brute force drive via that intermediary drive transformer.
Also, what are the numbers on the top two power devices.
We seem to be seeing quite a lot of these units coming into use now . . . . what with the price point aspect.
Reliability ? . . . .we will just have to wait and see.
73's de Edd
Here are the foil paths to component layout relationships on your units PCB.
I certainly would suspect the fuse, having been blown, if the unit below has any shorted internal diodes.
Your units Full Wave Bridge Rectifier is located halfway between the upper 115 / 230V selector switch and the lower pair of BLUE Y caps.
This fellow is testing the same cased unit as yours is having . . . . . . it's just being flipped 180 degrees hoz.
HEY I forgot to ask . . . . did you get any initial " Three Dee" printing done ?
Or did this units failure, stop you, just after the " Th. . . . . . . . . .".
The filament string heater and the units drive "moders" whiff up quite an amount of power !
BTW. . . . In case the info might be needed for your . . . or others . . .units in the future,
could you pass on the part number of the controller I.c. .
I can see that it's having too many pins for the common ua 384X series and it's feeding into
a pair of complementary transistors for brute force drive via that intermediary drive transformer.
Also, what are the numbers on the top two power devices.
We seem to be seeing quite a lot of these units coming into use now . . . . what with the price point aspect.
Reliability ? . . . .we will just have to wait and see.
73's de Edd
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Thank you for the pictures and video. I followed the video and it looks like when I test the positive to ac on the left it gives a reading and when I swap them I get a reading. So that means that diode is bad right? All the other ones worked like the video but I have a feeling its all or non when it comes with this stuff. Hopefully that made sense.
So if the fuse isn't blown but the rectifier is bad does that mean something else has failed?
I did get a few prints done before the power supply stopped working. I assume the heated bed would be the biggest power consumer since its main power wires go directly to the power supply and not to the controller for the printer, and the heated nozzle would be the next power consumer followed by the 5 nema 17 motors, I dont think the lcd screen would consume a meaningful amount of power. im not to sure what the actual numbers are on the heated devices im gonna look into it and see what I can find. I didnt quite understand the last part. the part number to what controller?
So if the fuse isn't blown but the rectifier is bad does that mean something else has failed?
I did get a few prints done before the power supply stopped working. I assume the heated bed would be the biggest power consumer since its main power wires go directly to the power supply and not to the controller for the printer, and the heated nozzle would be the next power consumer followed by the 5 nema 17 motors, I dont think the lcd screen would consume a meaningful amount of power. im not to sure what the actual numbers are on the heated devices im gonna look into it and see what I can find. I didnt quite understand the last part. the part number to what controller?
73's de Edd
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I would guess that you are leaving the full wave bridge in circuit and testing .
If this is the case, move the slide switch up to the 230 position, this will take the electrolytic capacitors out of circuit .Be sure to return the switch back to 115 after testing.
Confirming your test procedure:
Set up your meter just as you were testing before, and short together the test prod leads .
That is the type of numerical reading that you would be getting on a totally shorted diode .
The low readings in the 400-800 range would be almost the same on all four diodes .
I have the controller i.c.'s position marked up for you on the sheet, in two different places.
73's de Edd
.
If this is the case, move the slide switch up to the 230 position, this will take the electrolytic capacitors out of circuit .Be sure to return the switch back to 115 after testing.
Confirming your test procedure:
Set up your meter just as you were testing before, and short together the test prod leads .
That is the type of numerical reading that you would be getting on a totally shorted diode .
The low readings in the 400-800 range would be almost the same on all four diodes .
I have the controller i.c.'s position marked up for you on the sheet, in two different places.
73's de Edd
.
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