Hi , I've got an 550W ATX PC power supply and I changed it like this: [reprap.org]. If I turn on the heated bed on RAMPS 1.4 the PSU is turn off, and this is the same problem if I connect it directly to the PSU. My question is what is the reason, why is this happens? The PSU can provide 22A on the 12V rail. Everything works fine just the heated bed turns off the PSU. I don't know what need to do, i hope anyone offer some advice? https://reprap.org/forum/read.php?13,221791,221791#msg-221791 Mon, 16 Mar 2026 10:38:58 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?13,221791,221997#msg-221997 https://reprap.org/forum/read.php?13,221791,221997#msg-221997 slymike Controllers Thu, 27 Jun 2013 08:11:14 -0400 https://reprap.org/forum/read.php?13,221791,221996#msg-221996 https://reprap.org/forum/read.php?13,221791,221996#msg-221996 Are your resistors wired in a chain Like this (psu +)------(res)-----(res)-----(res)-----(res)-----(psu -).??
If so Your readings should be Ohm value x number of resistors. if not then you may have shorted against the aluminium bed.(assumuming you have 4 resistors screwed to an aluminium bed)
hope that helps, give it a good viisual inspection and double check your wiring (whole system) for mistakes.]]> slymike Controllers Thu, 27 Jun 2013 08:06:24 -0400 https://reprap.org/forum/read.php?13,221791,221993#msg-221993 https://reprap.org/forum/read.php?13,221791,221993#msg-221993 markmotor Controllers Thu, 27 Jun 2013 07:57:32 -0400 https://reprap.org/forum/read.php?13,221791,221971#msg-221971 https://reprap.org/forum/read.php?13,221791,221971#msg-221971 markmotor Controllers Thu, 27 Jun 2013 06:33:02 -0400 https://reprap.org/forum/read.php?13,221791,221969#msg-221969 https://reprap.org/forum/read.php?13,221791,221969#msg-221969 markmotor Controllers Thu, 27 Jun 2013 06:26:38 -0400 https://reprap.org/forum/read.php?13,221791,221958#msg-221958 https://reprap.org/forum/read.php?13,221791,221958#msg-221958 That would deffo upset your PSU.

I fried a High Side Driver (VNO5) that I was trying and experienced a similar problem.... So if you are using a SSR, FET, HSD, LSD, also check the in and out pins with a meter (whilst the control board is off) to see if your devices is fried (internally shorted), if it is you will get a very low score, again less than an ohm. If its a HSD check connection between output pin and ground, it should be open circuit, if not...its dead. Same with LSD but between output and +v rail, disconnect heater first.]]> slymike Controllers Thu, 27 Jun 2013 05:26:56 -0400 https://reprap.org/forum/read.php?13,221791,221802#msg-221802 https://reprap.org/forum/read.php?13,221791,221802#msg-221802 reprap.org]]]> nophead Controllers Wed, 26 Jun 2013 15:49:04 -0400 https://reprap.org/forum/read.php?13,221791,221791#msg-221791 https://reprap.org/forum/read.php?13,221791,221791#msg-221791 reprap.org]. If I turn on the heated bed on RAMPS 1.4 the PSU is turn off, and this is the same problem if I connect it directly to the PSU. My question is what is the reason, why is this happens? The PSU can provide 22A on the 12V rail. Everything works fine just the heated bed turns off the PSU. I don't know what need to do, i hope anyone offer some advice?]]> markmotor Controllers Wed, 26 Jun 2013 15:02:12 -0400