Canon AC/DC transformer with 24V CONT GND, CONT=? - Page 1
Forum section: electronics / beginners

author: NielsVdk
author_rank: Newbie
timestamp: October 22, 2015, 03:39:54 pm
content: HelloI did a tear-down on a Canon MP140 and I found a transformer from 220V to 24V, but there is a catch: it has 3 pins:24V, CONT, GNDAfter googling I found that Cont stands for control and it is used to bring the transformer out of it's standby-mode (please correct me if I am wrong).Well now to the question: how do I wire the CONT pin?Some sources say they connected it with the pin 24V from the transformer (but with resistors in series).Does anyone have experience with this? I don't want to blow up this transformer because it's the only 24V source I got.Please note: I don't have a oscilloscope to read out anything nor a variable voltage source for testing the CONT connection.

author: Cald0s
author_rank: Newbie
timestamp: October 22, 2015, 05:00:04 pm
content: Hi Niels,Can you post a picture of the transformer? Also do you have a multimeter? We will get to the bottom of this yet.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 22, 2015, 05:32:33 pm
content: its not a transformer, its a smps psu. it got a transformer inside allright, but thats not just it.. i dont think cont is to put the psu into standby or it will simply shutdown the printer hard-off'ed

author: NielsVdk
author_rank: Newbie
timestamp: October 22, 2015, 09:28:14 pm
content: HelloHere is a picture of the Canon AC adaptor K30270:(it's just a plastic box with a power cord attachment, 3 pins and this text on it)I do have a cheap (€5) multimeter, it isn't very good but it will do.Measuring the resistance between:24V and Cont: 27.6 K?24V and Gnd: 11.70 K?Cont and Gnd: 14.2 K?Mechatrommer: Thanks for the info, then maybe the 24V connection is for the printer motors? Shutting them down with cont to save electricity?

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 23, 2015, 03:24:38 am
content: Quote from: NielsVdk on October 22, 2015, 09:28:14 pmno its not just a plastic box, you havent dig deep enough, i have trillions of this plastic box just not for the MP140 iirc.. i am a printer salvager nuts.Quote from: NielsVdk on October 22, 2015, 09:28:14 pmyes 24V is for printer motors, but depending on what is CONT really is (i'm not sure) 24V also possibly powering all the electronics and printer's brain. but if CONT is like 3.3V output, then it can be to supply them, hence no standby mode, as i'm expecting...

author: rs20
author_rank: Super Contributor
timestamp: October 23, 2015, 03:28:36 am
content: Resistance isn't terribly informative (the connections won't be ohmic). Can you plug it in and measure the voltage across the same pairs of pins? This is no different to plugging in the wall plug before plugging the plug into the printer; so it is sure to be safe.

author: NielsVdk
author_rank: Newbie
timestamp: October 23, 2015, 07:22:11 am
content: Quote from: Mechatrommer on October 23, 2015, 03:24:38 amWell with plastic box I meant it's a double insulated electric box. Opening it probably means destroying the box.Quote from: rs20 on October 23, 2015, 03:28:36 amI thought so too, but as it was the first time I would measure out a 'live' component I wanted to be awake and yesterday night I was too tired.Voltages:24V to GND: 7.2V24V to cont: 7.0Vcont to GND: 0VBy looking at this: would it be correct to assume that CONT is indirectly connected with GND?

author: rs20
author_rank: Super Contributor
timestamp: October 23, 2015, 08:52:48 am
content: (Edited because I misread earlier)Well, there could just be a pull-updown resistor from cont to24VGND, and pulling the contdownup toground24V turns on the 24V to a proper 24V. ATX power supplies have a very similar arrangement (albeit it's a pull-up resistor that you pull down to ground).Just shorting it out with a wire is a bit risky, though. Try a 1k resistor from cont toground24V, maybe? And see how both 24V and cont respond. That's what I'd do, not taking any responsibility though.

author: NielsVdk
author_rank: Newbie
timestamp: October 23, 2015, 11:32:22 am
content: Quote from: rs20 on October 23, 2015, 08:52:48 amResistor between cont and ground: no effectResistor between 24V and cont: voltage changesWhen using a 100K resistor I get a voltage of 21.1V................. 10K resistor....................... 23.8V................. 1K resistor ........................ 24.6VIt could be that the voltage difference is because of my cheap multi-meter, but the results are clearConnecting the 24V line with the CONT line does increase the voltage of the 24V line.Maybe one last question: is this the principle of a pull-up or a pull-down resistor?

author: NielsVdk
author_rank: Newbie
timestamp: October 23, 2015, 12:43:07 pm
content: Quote from: rs20 on October 23, 2015, 12:03:23 pmActually I said 7.0V (=7,0V). Sorry for any unclarity on my behalf.

author: rs20
author_rank: Super Contributor
timestamp: October 23, 2015, 01:00:31 pm
content: Quote from: NielsVdk on October 23, 2015, 12:43:07 pmJust looked back, and it was me that misread. My fault, sorry! I've edited and deleted earlier messages accordingly.In summary, the results you see are consistent with the power supply have a pull-down resistor on the "cont" line.

author: NielsVdk
author_rank: Newbie
timestamp: October 23, 2015, 01:12:17 pm
content: No problemThanks for the explanation.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 02, 2015, 04:00:15 pm
content: Quote from: NielsVdk on October 23, 2015, 07:22:11 ami managed to open a canon ip1880 psu, similar pin out as the OP, you maybe solved your problem by now but fwiw for future reference... cont is connected to a transistor base that is pulled down by resistors to GND... the transistor then will turn on something that is not my interest (optocoupler and then to the hot side). during turning on 24V pin will read 7V but if you pull up (short) the cont with this 7V output, you will get 24V output. so i guess cont is for control when we need high demand of 24V, during idle, cont is gnded and psu is low voltage mode of 7V. i believe it is safe to short 24V pin to cont, since cont to the transistor base has a resistor in the middle, not interested to now the value, only interested in making it output 24V or until it blows up, my spare is expendable anyway, i got many more spares. fwiw...

author: teknosrp
author_rank: Newbie
timestamp: January 30, 2020, 06:53:36 pm
content: HelloI just arrived to this thread looking for the pinout of a K30330 power supply, used in canon PIXMA MG2120 and MG3120 models. It works just the same way of the other models posted here, but this one hasn't got the pin names marked at the outside. After measuring and trying, this is the correct pinout:(Side of the AC outlet) GND - CONT - 24VAnd for powering it up, just short these last two pins.

author: ccare
author_rank: Newbie
timestamp: January 02, 2021, 10:26:59 am
content: Greeting and happy new year to all,i have a question, on this thread.it is possible to replace the original adapter with a regular one 24v +/- ?the adapter just stopped working. i provide 24v to 24v - GND but i take no signal. only 0.003A. the machine does not turn on.do i have to provide 24v to CONT aswell?Thank you

author: Munko
author_rank: Newbie
timestamp: October 05, 2021, 02:58:35 pm
content: Hello, I have the same source, I managed to open it, you just have to make a bridge between the 3v (Central Pin) and the pin on the left, the pin on the right is the GND, with that it activates the reference of the T431 and the output is from 24 - 25v, the center pin has a resistor that goes to a transistor that drives the negative reference of the internal transformer output

author: Afinch56786
author_rank: Newbie
timestamp: December 06, 2023, 04:36:21 am
content: THANKS FRIEND. YOU SAFE ME.