Power supply - How to turn it on? - Page 1
Forum section: electronics / beginners

author: almamater
author_rank: Regular Contributor
timestamp: July 12, 2020, 02:35:35 pm
content: Hello.I have one question about one power supply (that I didn't throw away because I think it can be used for anything else) it came from a printer or something similar. It has 24v and 5v outputs.I tried to turn it on but the 24 \ 5V outputs were 0v. Only 1 pin had 3v.I think there has to be a small current to activate it. From what I see on PinOut it has 2 pins that will connect to aPHOTOCOUPLER"Cosmo 3052", which in turn is connected to a TriacBTB24-600BW.As at PinOut only 1 pin has 3v, my question is: should i connect the 3v to those 2 pins that connect at photocoupler? (the +3V to photocoupler Anode and Gnd to the photocoupler Cathode). Its correct?Sorry for the basic question but it is better to ask than to screw up. Thanks

author: Manul
author_rank: Super Contributor
timestamp: July 12, 2020, 06:57:44 pm
content: I don't know if I will help you, but I strongly believe that triac is used to drive a heater in laser printers and should not be a power supply switch.Usually soft switchable power supplies have separate standby supply (5 or 3.3V) and enable pin (active high, active low or both). May also be possible that it is just a high pin, which enables supply when taken low (by mechanical switch). Investigate your 3V pin, is it pulled-up "logic" pin or is it standby supply.

author: firewalker
author_rank: Super Contributor
timestamp: July 12, 2020, 07:05:26 pm
content: This seems to be the pin out of the board the PSU connects. I believe you just need to power it with mains and pull low pin 1 (the 3 volts you are measuring).Alexander.

author: almamater
author_rank: Regular Contributor
timestamp: July 12, 2020, 09:09:51 pm
content: Thanks for the answers Manul and firewalker !The Pin out is correct!! wonderfull!So, im my case, i measured the 3 volts atpin 7(ACZEROX). It must be StandBy mode..Probably i must connect the pin 1 to Ground.. as you said! i can try that

author: Manul
author_rank: Super Contributor
timestamp: July 12, 2020, 09:39:18 pm
content: Quote from: almamater on July 12, 2020, 09:09:51 pmHmm..If pinout is correct, it must be AC zero cross signal which I suppose is used by triac control circuit. So something is not matching here.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 13, 2020, 07:27:30 am
content: Why does it look like it has 2 AC inputs?

author: almamater
author_rank: Regular Contributor
timestamp: July 13, 2020, 11:13:24 am
content: Yeah.. it has a 220v output.. I honestly don't remember how everything was connected, it was some time ago that I disassembled this.But the second Power connector is an output.. because an i have 220v from there

author: firewalker
author_rank: Super Contributor
timestamp: July 13, 2020, 11:22:54 am
content: Quote from: PA0PBZ on July 13, 2020, 07:27:30 amI think the second connector is for supplying the fusser via the triac. Maybe the second C14 plug is from another psu that was just put there?Alexander.

author: almamater
author_rank: Regular Contributor
timestamp: July 14, 2020, 10:31:54 am
content: Thanks everyone for your answers. I figure it out! I searched for the printer\service manual and i found this:So, i put one 69.9R resistor between those pins and voilá:http://youtu.be/S9qVDE0PhwoThe 24v output it's a little low (~22v) but oK... probably are the capacitors..