No Power In Samsung ML-4050N Laserjet Printer
This printer was sent to my partner for repair and the complaint was no power. For your information my partner Mr William doesn’t repair electronics board. If he encounters any electronics problem in printers he will ask me to troubleshoot and repair it. He is more specializing in the mechanical area/fusing/printer head of printers. He told me that it was not easy to remove the power supply board as one needs to dismantle many parts before you have the easy access to it.
Actually there are two circuit boards-one is the high voltage board and the other one is the power supply board. Since the complaint was no power so I concentrate on the power supply board. The first thing to check was the main fuse and it was tested good. There were no bulged electrolytic capacitors and while trying to search for any burn component I found a component marked as TH1 already cracked and hardly could see the whole part number. This component is a Thermistor while to some they refer to is as Thermister. Not only that, the heatsink located just behind the Thermistor had a burnt mark caused by the great spark of the Thermistor when it was exploded most probably due to the excessively high inrush current. Just to let you know that one of the main function of a Thermistor is to used as inrush current limiter.
A good Thermistor when testing it with Ohm meter it should show low Ohms reading. This particular Thermistor does not show any reading which means it is already open circuit. Please take not on this- whenever you found a burnt or open circuit Thermistor, you need to check the corresponding components as well. The main fuse did not blow does not mean other power semiconductors are good.
In my case, I did checked on the power FET, primary winding of the transformer and secondary diodes and all of these components were tested good. I’d also put special attention on the SMD power IC to see if there is any tiny burnt mark on the surface of the IC with the help of my X35 magnifying glass. Well, the SMD IC and the surrounding SMD components were in good condition too.
From the above simple scan through test I concluded that only the Thermistor having problem and I believe by replacing only the Thermistor could solve the problem. The question now is where to find the exact replacement since I could not trace the original part number datasheet? I left only two choices-either just connect a wire across it or use a replacement number. For your information if you use a wire as a replacement, then the power supply no longer have protection against inrush current. In the future if there is any excessive inrush current, many of the primary side components will be badly affected.
Since my store room has some junk Laserjet power boards, I took out a good Thermistor and used it as a replacement. My expectation was correct; the Laserjet came back to life once the AC power is applied. For your information, you need to turn On and Off the power many times to see if the replacement component is stable or not. If the replacement component has a too low spec then it may blow again. So, the best is to try On/Off the power supply many times before sending it back to your customer.
Conclusion- Not all switch mode power supplies are using Thermistor as protection against inrush current. I have seen many power supplies used low ohm wire wound resistor ranging from 2.2 to 4.7 ohm 5 to 10 watt as inrush current limiter. Some does not even have any of these components in their design. In the above case, fortunately only the Thermistor have problem. In some cases, a blown Thermistor could cause the power FET, power IC and corresponding components to blow as well and surely this will take more time and skill to troubleshoot it.
Hope you have enjoyed this repair article. Your feedback on the post is welcome. Please leave it in the comments.
Jestine Yong
Latest update: Just found the datasheet for both the Thermistors:
For more information about Varistor and Thermistor function please click on the links below:
http://en.wikipedia.org/wiki/Varistor
http://en.wikipedia.org/wiki/Thermistor
Click Here to Learn Basic Laserjet Printer Repair
Click Here To Learn Printer Head Repair
(21)Dislikes
(0)
112 Comments
Leave a Reply
noel gervais gerard
July 24, 2012 at 10:28 am
HI sir thank for the repair articles its good to know how a thermistor works in a switch mode power supplies primary section thank again
bogie
July 24, 2012 at 11:14 am
Thank you very much for this blog Sir, a great input and save to memory...
Lawrence Pina
July 24, 2012 at 11:15 am
Regarding the HP Laserjet 2200 (or any other HP Laserjet) with a sticky relay: check for a (brown) felt, stick-on pad underneath the spring-loaded relay lever. This function of this pad is to reduce (relay clack) noise. In my experience, the glue penetrates the felt creating a sticky mess on the opposite side. That is why the lever is sticking. Solution: Scrape away the pad. Clean off any remaing sticky residue with Goo Gone or alchol and except for increased noise, you should be all set.
Jestine Yong
July 25, 2012 at 6:44 am
Hi Lawrence,
Thanks for the tip!
Jestine
Billy
July 25, 2012 at 12:37 am
Thank you Mr Yong, enjoy your news letters and your e books,keep up the good work..
kalimasraf
July 25, 2012 at 1:31 am
Hi sir,
i want to learn how to use a blower for smd also if u can suggest which type of blower is better .since am too far from u n i want to learn a lot from u sir if u can help me plz i really need to learn this
Jestine Yong
July 25, 2012 at 6:43 am
Hi Kalimasraf,
Try youtube.com as there are lots of videos about using the SMD rework station.
Jestine
Nimal
July 25, 2012 at 4:32 am
Thank you Mr Jestine Yong. Your explanations are very simple and easy to understand.
geoser
July 25, 2012 at 4:46 am
thanks alot sir justine..a big show that i realy now...but her in my place i always repairing for that kind of power supply.
Okore Kingsley
July 25, 2012 at 5:57 am
Hi Jestine,
Thanks for the News letter I have been trying to differentiate between the two component for a ling time now, sir can a Varistor be used to replace a burnt themistor? in a situation where I cant get the themistor to buy in my location.
Jestine Yong
July 25, 2012 at 6:42 am
Hi Okore,
You can't replace a Thermistor with a varistor. A good Varistor is open circuit while a Thermistor have resistance value.
Jestine
Paulo
July 25, 2012 at 6:06 am
Good day Sir Jestine,
Thank you for the newsletter..Very helpfull..Do we have forum here so that we can discuss a specific topic in repairing?...so that we can share our knowledge and some techniques...
MOre power!
Jestine Yong
July 25, 2012 at 6:43 am
Hi Paulo,
Sorry I do not have a forum. If you have any question you can just post in this blog.
Jestine
ZIMBE
July 25, 2012 at 9:17 am
i have a transistor am looking for but its part number is confussing me can i send you its picture in an email
Jestine Yong
July 25, 2012 at 8:52 pm
Hi Zimbe,
Yes you can send to jestineyong(at)electronicrepairguide.com
Jestine
Ting Ban Kang
July 26, 2012 at 1:34 am
Hi Jestine,
Long time no contact you.Hope you remember me-not a technician,but just DIY/hobby enthusiast.I have two printers-Canon Pixma M318(use for photo prints only) & Canon iP2770( for rough use & also photo prints). Need advice on iP2770 which print out unsatisfactory colour. Done all the tricks under "maintenance" many times & also cleaned the two small foam pads inside. The colour prints shows white streaks horinzonta lines & light green background.Advise? Any suggestion to get good branded printer for photo prints only?
Jestine Yong
July 27, 2012 at 10:31 pm
Hi Ting,
Yes I remember. In your case the print head may have clogged. There are videos in youtube that teaches how to unclog the print head. If you wants to buy a new printer I suggest that you get the one where the printhead and the color ink are built into one such as HP printer. You may need to check from the seller to find out the latest model.
Jestine
abbas
July 26, 2012 at 1:01 pm
sir, somebody gave me DVD player for repair.the problem is the system only play CD not DVD, but initially was playing both DVD and the Cd.tnx
Jestine Yong
July 26, 2012 at 11:51 pm
Hi Abbas,
Check the spindle motor. if the motor is weak it could only run on CD and not DVD.
jESTINE
kate
July 27, 2012 at 9:16 am
Hi Jestine,
i have a DVD player which only has a sound but no picture,i've checked the cable behind they are all OK i believed some thing when wrong inside could you tell me which part of the board i should check..
Jestine Yong
July 28, 2012 at 8:39 pm
Hi Kate,
You should check on the mainboard.Usually this kind of problem is hard to diagnose due to no parts available.
Jestine
shahid
July 27, 2012 at 10:04 am
i am really pleased to read this article.
it was so easy and clear to understand.
Nichole
July 28, 2012 at 3:33 am
Hi Jestine,
Thank you very much for finding time to give this yet another invaluable resource of knowledge. Keep it up! Regards and until then. God bless you.
Nichole
sodjah
July 28, 2012 at 3:47 am
very helpful thanks
Del Corso A.
July 28, 2012 at 7:13 am
Good Article!Tank You:
Marcel
August 4, 2012 at 6:25 am
hi, jestine how are u i m enjoying ur articles every month. thanks
i have a problem with my tv. no picture but sound. high voltage transformer fine, no light at the bottom of the tube. assuming tube fine where else can the problem be found?
marcel
Jestine Yong
August 4, 2012 at 10:02 pm
Hi Marcel,
Have you check the tube heater resistance? If there is high voltage then there must have ac pulse to the heater and the heater will surely lights up.
Jestine
nuwan tharaka
August 7, 2012 at 9:29 am
very usefull, I learned lot of things with the reference of these documents so thank u very much and any future uploads also will be thankfully welcome. Thanks!
kelvin chambula
August 10, 2012 at 9:00 am
hi jestin,
what can couses the lg led tv to show bottom vertical shawes ? could it be t-con or main board?
Couse i checked on the t-con i found that the voltage is left conection to right conection which was 10v . and other was 15v advise.
Jestine Yong
August 14, 2012 at 1:25 am
Hi kelvin,
Could you send to me the photo to jestine(at)electronicrepairguide.com . (at) means @
Thanks.
Jestine
Akhlaq
October 4, 2012 at 12:07 am
Very interesting artical. Easy language and best illustrations. Thanks.
Md Imran
October 21, 2012 at 6:03 am
Hi admin this component is a part of Xbox psu it got cracked due to surge http://img152.imageshack.us/img152/3449/1350730827393.jpg is it a varistor or thermistor I have mov 250 v can I replace it with this
Jestine Yong
October 21, 2012 at 9:39 am
Hi Mohd,
It is is connected in series with the live line then it is a thermistor and if it is connected in between live to neutral, live to ground or neutral to ground then it is a MOV. If your country is using 220v then you can replace the MOV with 250volt.
Jestine
Md Imran
October 22, 2012 at 1:27 am
Thanks a lot for the reply jestine you are awesome guide I am like a beginner in all this I can solder and de solder but not good in finding If it's in seriers please tell me http://img198.imageshack.us/img198/8438/1350801908762.jpg
Jestine Yong
October 22, 2012 at 10:18 pm
Hi MD,
Check from the internet what does it mean by series circuit and you will understand it clearer. If your component is in series then it is a thermister.
jestine
vincent
November 28, 2012 at 9:48 pm
Great article.I wanted to know the use of varistor in this component.I learned that
<a href=”http://http://www.resistorguide.com/varistor/”>voltage dependent resistor like metal oxide varistor give urge protection & protection from high voltage spark</a>
Fred
August 14, 2013 at 7:20 am
Hi Jestine, hi find a total exploded and burnt varistor, if schematic not available how to know what type of varistor is suitable for replacement?
Thank you
Jestine Yong
August 14, 2013 at 10:02 am
HI Fred,
If your country is using 240 vac then you can buy a 260 to 270 vac VARISTOR.
Jestine
Amir Mukhtar
December 12, 2013 at 4:17 am
Sir Jestine
Thanks you for your realtime professional electronic repair solution
thanks you sir
yours student
Amir Mukhtar
Jestine Yong
December 12, 2013 at 10:16 am
Hi Amir,
You are welcome!
Jestine
GIRISh Wagh
April 2, 2014 at 7:51 pm
surely, if any amateur ask you a question How to repair Electropics things? then you will definitely make him the master.
Gurpreet
September 5, 2015 at 10:17 pm
Hello dear
Good job and thanks for sharing this article.
Carlos Max Andres
February 7, 2017 at 8:51 pm
Hi!
Does anybody here know which IC is the SMD power controller (IC505) for HP M401DNE (CF399A)? Its face has the inscription "ID13101".
Thank you very much!
Jestine Yong
February 8, 2017 at 8:56 am
Hi Carlos,
If the primary power section have only one IC then that IC is the power controller IC.
Jestine
Bob Tran
July 7, 2017 at 2:45 pm
Wow found your article online and the fault you discribed above is exactly what happened to my laser printer ml4551nd. Initial observation seems to be the same. Trying to get that cap and replace to see if i can get the power back on.
Thanks and great info
Best Regard
Bob Tran
Jestine Yong
July 7, 2017 at 10:07 pm
Hi Bob,
You are welcome.
Jestine
fabio
April 10, 2020 at 8:23 pm
my experience i check voltage 2 line of 24v and no 5v. PIN of conponent TOP44YN are short. cause radiator not perfect close for dissipation. After change component 5v Is back and no 24v. Is strange for me... i check Google PDF info Is normal! provide signal for standby 24v off. complete cable and riassembly machine Power on all okay!!!