No Power In Panasonic Fax Machine Solved
One of my customers sent me a Panasonic Fax machine (Model: KX-FP343ML) and the complaint was no power. In order to see the power supply, one has to remove the cover located at the bottom of the machine. Few screws removed and you could see all the circuit boards and power supply inside as seen from the photo below:
The first component I checked was the main fuse and I found it had open circuit. When a fuse have problem it could mean the fuse can break by itself after serving for few years or there are some shorted components causing the fuse to blow. I proceeded to check on some of the major components in the power primary side like the Thermister,Varistor, bridge rectifier diodes and power FET.
I found two of the four bridge diodes had a short circuit but the power FET was tested good. Since the power FET was tested good then chances for the power IC and secondary output diodes to have problem will be very slim. I did not stop there instead I proceeded to check on the main filter capacitors and also secondary side filter capacitors with my Blue ESR meter to see if there is any marginal capacitors. There are no marginal capacitors detected.
Marginal capacitors means they have higher than normal ESR value but have not reach to the bad/critical level yet. If you did not replace the marginal capacitors, most probably after couple of months or a year the capacitors will breakdown and give problem. Worst if those marginal capacitors give intermittent problems. You will have a hard time troubleshooting such faults.
The two diodes that was shorted had a part number of 1N4005 and I replaced all the four diodes with 1N4007 which have a higher voltage but same ampere. For your information you can replace diodes with the same or higher voltage and ampere but not lower. The reason I replaced the other two working diodes is because somehow I believe the other two working diodes will break down again in a short time. I have experienced this before and this is why you need to replace all the four diodes (even if you found one of the four diodes have problem) if you don’t want repeated call from your customer. A repeated call means a loss in your repair time. The fax machine was back in working condition after the diodes and the fuse were replaced.
Note: I did not use the light bulb test because I’m confident that only the fuse and the diodes have problem. Actually it is your preference whether to use the light bulb test or not. If you have no confident then you have to use the light bulb test.
If you already have the basic in electronics repair and would like to increase your knowledge in troubleshooting and repair power supplies, I suggest that you get my ebook HERE. It has many repair techniques that can turn you to become a professional in troubleshooting and repairing power supplies.
This article is brought to you by Jestine Yong
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Anwar Shiekh
October 18, 2014 at 10:24 am
Another fine repair; like many people here I am addicted to such success.
Jestine Yong
October 18, 2014 at 10:26 am
Hi Anwar,
Thanks.
Jestine
Eric
October 18, 2014 at 10:37 am
I was wondering if you do hands on clases? And where do you do them? If you do? Or when can i get info on thhe classes?? Thank You??
Jestine Yong
October 18, 2014 at 10:45 am
HI Eric,
Please visit this website http://www.NoahtechElectronicsTraining.com
Jestine
Supriyo Pal
October 21, 2014 at 12:45 am
Sir, Is there Online courses of you?
Jestine Yong
October 21, 2014 at 10:06 am
Hi Supriyo,
Yes please visit the link below:
http://www.noahtechelectronicstraining.com/lcd-monitor-repair-online-exam
Jestine
Wes
October 18, 2014 at 10:40 am
Very good article and photos were great. Diodes are a common problem in units like this. Just repaired a machine very much like the one you repaired, with some diode failures and a open thermistor.
Very good on replacing all the diodes. I have also found this to be a good practice. Thanks for a nice article...Wes.
Jestine Yong
October 18, 2014 at 10:46 am
Hi Wes,
You are welcome!
Jestine
tim
October 18, 2014 at 11:33 am
Another great repair article by mr Yong! I enjoy reading the repair cases, and never miss one, cause its almost as if I did that repair myself. I do wish I had more time to practice, but so far still at hobby level. Keep up the good work, and keep the articles coming!
Jestine Yong
October 18, 2014 at 11:50 am
Hi Tim,
Thanks.
Jestine
Tito
October 18, 2014 at 12:31 pm
Mr. Yong,can't there be a problem with other components around the circuit,especially when you change diodes value from IN4005 to IN4007?
Jestine Yong
October 18, 2014 at 12:45 pm
HI Tito,
Replacing with a higher spec of diodes would not affect the other components.
Jestine
Rudi Wijaya
October 18, 2014 at 12:51 pm
Great repair sir ! I learn many thing from your article. Thank you.
Jestine Yong
October 18, 2014 at 12:54 pm
Hi Rudi,
Thanks.
Jestine
Osman Alsinnary
October 18, 2014 at 2:40 pm
Very helpful repair article ...
Thanks
Jestine Yong
October 18, 2014 at 2:44 pm
Hi Osman,
You are welcome!
Jestine
megamind
October 18, 2014 at 2:45 pm
having problem with dell charger the fet source resistor got burnt when i changed it got burnt again what can i do sir
Jestine Yong
October 18, 2014 at 5:31 pm
Check all the surrounding components. If the load draw more current than the charger can supply, the resistor also will burn.
Jestine
Sonwabo Nothole
October 18, 2014 at 3:42 pm
Very helpful information indeed thanks Jestine.
Jestine Yong
October 18, 2014 at 5:22 pm
HI Sonwabo,
You are welcome!
Jestine
Yogesh Panchal
October 18, 2014 at 5:29 pm
Sir,
you are really have a passion in this field , else i have seen many repairer who just deny the repair this type of products.
thanks for sharing your experiance.
Jestine Yong
October 18, 2014 at 10:22 pm
HI Yogesh,
You are welcome!
Jestine
Yogesh Panchal
October 18, 2014 at 5:55 pm
sir i want to add my photo in comments pls. guide
Jestine Yong
October 18, 2014 at 10:22 pm
HI Yogesh,
Go to https://en.gravatar.com/ and sign up free using your email. After that your photo will appear in any blog you comment.
Jestine
Bradley
October 18, 2014 at 9:07 pm
Very good article, Jestine, as usual.
Jestine Yong
October 18, 2014 at 10:18 pm
HI Bradley,
Thanks.
Jestine
reza
October 18, 2014 at 9:40 pm
hi
good article
thanks mr yong to send this email .
Jestine Yong
October 18, 2014 at 10:17 pm
HI Reza,
You are welcome!
Jestine
Mike
October 18, 2014 at 10:26 pm
Thx for taking us through this. Learning all the time. Well done Mr Yong
Jestine Yong
October 18, 2014 at 10:37 pm
Hi Mike,
You are welcome!
Jestine
beh
October 18, 2014 at 11:13 pm
good post and good explanations for retired caps
Tyrone
October 19, 2014 at 2:23 am
Very good Jestine.
Austin
October 19, 2014 at 3:12 am
congratulation jestine, I'm very greatifully as you always teach us how to repair electronics perfectly without having call back of customer,not all engineers will teach us all those things you use to teach,may God bless you and reward you,thanks.
Abdul
October 19, 2014 at 8:40 am
Dear Jestine,
Thank you for the article, I hope more will come.
I am addicted to read any articles from you site.
Most of my mentors has gone.You are my referral now.
Hope some day we will meet in person.
Taring K Arioka
October 19, 2014 at 11:28 am
Many words of thanks for this very nice article.
biruk aweke
October 19, 2014 at 12:39 pm
HI Mr.jestine thanks very much it is very nice article bay the way i just change my life when i contact from you God bless you.you are great.
Jestine Yong
October 19, 2014 at 1:52 pm
Hi,
Thanks to all!
Jestine
Sohidbd
October 19, 2014 at 3:24 pm
Hi Mr.jestine thanks, Very helpful tips.
Salim Khan
October 19, 2014 at 10:19 pm
How do you check Thermistor & Varistor?
Jestine Yong
October 20, 2014 at 1:52 pm
HI Salim,
I suggest that you visit these articles:
https://www.jestineyong.com/metal-oxide-varistor/
and
https://www.jestineyong.com/no-power-in-samsung-ml-4050n-laserjet-printer/
Jestine
Venu Gopal
October 19, 2014 at 11:32 pm
very good article.Thank you!
Patrick Yun
October 20, 2014 at 8:25 am
Thank you for sharing of your skill. I very enjoyed your article and members.
When you test components you take each component out from board, right? except capacitor using Blue ESR meter.
Is it possible to find fault components using voltage test or other method?
Thank you.
Jestine Yong
October 20, 2014 at 11:12 am
Hi Patrick,
It depends on which type of component. To check a fuse, inductor, thermister no need to remove those components. To check semiconductors like diodes, transistors, zener diodes yes need to remove them. If you understand the circuit well you can find the fault using the voltage test method.
Jestine
Patrick
October 22, 2014 at 4:30 am
Thank you for giving good tips.You said "understanding circuit well", so what do I need to study about that? Didn't you make eBook about that? I've already purchased three of your eBooks,Testing Electronic Component,LCD Monitor Repair,SMPS Repair. But still studying and practicing to repair some LCD monitor and ATX power supply but never repair them yet. I'm a beginner.
Jestine Yong
October 22, 2014 at 11:13 am
HI Patrick,
Once you understand the circuit well you will know where/which point to start voltage probing. Ex: If the circuit is using a 3 pin 7805 voltage regulator ic then you should know that pin 3 is the 5 output and pin 1 is the input voltage.
Jestine
Robert
October 21, 2014 at 12:43 am
Good repair, Mr. Yong. Thanks for sharing with us.
Juan
October 21, 2014 at 2:52 am
I can see you are a profesional, I would like to have that knowledge as well but I want to start from the botton like study a eletricity course fist maybe you can send me something related to that.
Jestine Yong
October 21, 2014 at 10:08 am
Hi Juan,
Sorry I do not have electricity course. Try Google for it. In the meantime you can also try the link below:
http://www.repairfaq.org/REPAIR/
Jestine
Richard
October 21, 2014 at 8:24 am
HI Jestine,
I would like to take this opportunity to thank you, for sharing your repair knowledge with me. This information has enhance me.
Much appreciated.
raymundo saura
October 21, 2014 at 8:57 pm
thanks sir
Humberto
October 22, 2014 at 12:00 am
Hi Mr. Jestine Yong, good repair, explanations and photos, keep up and congratulations
Jestine Yong
October 22, 2014 at 9:11 am
Hi Humberto,
You are welcome and thanks to all!
Jestine
Andre Gopee
October 22, 2014 at 10:41 am
Excellent repair work once again Mr. Young. Love your articles. Keep them comming.
Mark Tembo
November 3, 2014 at 6:14 pm
Thanks Mr Yong. I found this article refreshing, especially on repairs of Power Supplies. Keep it up!
Julius
April 13, 2016 at 10:17 am
Hi Jestine, I have a fax machine Panasonic FX FP-343 for many years. I seldom use it. Recently, the machine has no power. I check the fuse of the machine according to yourrecommendation. It is OK. I know nothing on electronic and wonder whether it is worth to repair it. Please give your comments. Thanks
Jestine Yong
April 13, 2016 at 5:44 pm
Hi Julius,
Since you know nothing on electronics I do not advice you to proceed with the repair work because repairing the power section involve high current/voltage and can be fatal once you got electrocuted. You need an isolation transformer and understand the electrical safety in order to proceed with the work.
Jestine
fifi
May 22, 2018 at 1:32 pm
my Panasonic Fax/Copier suddenly stopped working last week. it is like it went dead. the cordless phone has low battery, but it won't recharge. how do i fix the fax/copier so i can recharge the cordless phone?
i have Panasonic KX-FPG378 and KX-FPG379
Jestine Yong
May 24, 2018 at 9:44 pm
Hi Fifi,
You need to open the set and check the power supply section for blown fuse, shorted components and etc. If you do not have the experience in electronics repairing, I suggest that you send to a repairer to do it as the power section contain high voltage that can be fatal to you if you do not know about the electrical safety
Jestine
Edukwu Victor
April 2, 2020 at 10:10 pm
My panafax UF-890 went dead after it was powered for a printout so I don't know if this procedure is applicable to the machine as am yet to know if the machine has a fused port
Jestine Yong
April 3, 2020 at 10:38 am
Hi Edukwu,
No power can be caused by many factors and many type of components can be faulty. Sometimes it can only be one bad single component. My procedure is just one of the ways to check the fault.
Jestine