Burnt Mark Found In Essen SMPS Model EPS-240-24 of An Autoclave Machine
This SMPS was brought to me in dead condition. On opening and checking the unit, I saw burnt mark near the primary switching SMPS transformer and also found one transistor C3320 short and one Zener diode 33V 1W short.
Checked SMPS transformers using the ring tester and found these to be ok.
The circuit had two ICs. One TL494 PWM and HA17358 dual Op-Amp:
The primary switching done at the small transformer was done through two driver transistors and fed to power transistors which were connected as Darlington pair. This was for ensuring high current gain as the SMPS was rated for 24V upto 10A current. The two tank capacitors were connected in series like in many Computer ATX SMPS.
The Second SMPS Transformer was large and provided the output. Over all it was a complicated SMPS circuit that provided 24V single output to handle the heavy load. I replaced both the power transistors and two 33V 1W Zener diodes.Removed the two tank capacitors and cleaned the burnt marks there. Replaced all the electrolytic capacitors except the tank capacitors (470uF/250V) as these were checked and found to be ok. Then retouched the board very well and cleaned it using IPA. The output showed correctly on applying power without giving any load. I had no bulb with me rated for 24V and did not have two 12V 25W bulbs to give it in series.
Click here to access the Switch Mode Power Supplies Repair Ebook
Anyhow, I allowed the SMPS to remain on for quite some time before closing the cover. The fan worked only when the temperature increased inside unlike the ATX SMPS.
The biomedical technician reported later that the unit was working very well in the Auto Clave unit.
Mission accomplished with satisfaction getting added to the collection.
This article was prepared for you by Parasuraman Subramanian from India. He is 76 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous article on Panel Replaced In Track Bypassed Nakamichi LED TV Model LEVX32
(38)Dislikes
(0)
16 Comments
Leave a Reply
Yogesh Panchal
March 21, 2026 at 4:21 pm
Good Fix! Sir
Parasuraman S
March 21, 2026 at 8:03 pm
Many thanks, dear Yogesh Bai!
Waleed Rishmawi
March 21, 2026 at 4:35 pm
I used to get a lot of these power supplies for repair and in my country they are being used in security cameras and LED lights in stores and show rooms unfortunately my customers think that they work for life and do not requier any maintenance and now a days there are a lot of them china made and they are very cheap to replace therefore not worthy to be fixed or maintaned. have a blessed day and thanks for sharing.
Parasuraman S
March 21, 2026 at 8:04 pm
Yes, there are a lot of cheap models available in the market! Many thanks for your comments, dear friend!
Albert van Bemmelen
March 21, 2026 at 7:08 pm
As expected another interesting smps unit repair professionally checked, explained and fixed! Thanks for sharing Parasuraman!
Parasuraman S
March 21, 2026 at 11:30 pm
Many thanks for your expert comments, dear Albert!
Mark Rabone
March 21, 2026 at 8:12 pm
Well done Parasuraman,
More electronic components saved from landfill!
Parasuraman S
March 21, 2026 at 11:38 pm
Many thanks for your comments!
Mark J
March 22, 2026 at 3:31 am
Parasuraman do you repair a lot of bio-medical equipment? It seems like you come across kinds of things to repair at your job. Good job on the repair.
Parasuraman S
March 22, 2026 at 1:01 pm
Yes, I have been lucky enough to get varieties of electronic devices and gadgets for repair. Recently I have stopped taking CRT TVs and Microwave Ovens as they are too heavy and I cannot handle them alone. I donated all my stock of spares and checking equipment to my techie friends as they are all very generous to help me as and when I require. Many thanks for your comments and encouragement, dear Mark!
Mark J
March 23, 2026 at 2:43 am
I think its fun and educational to repair a variety of devices and electronic equipment. One week I would be doing laptop's and compact disc players and the next week vacuum cleaners.
Parasuraman S
March 23, 2026 at 8:23 am
Yes, it is indeed fun & pleasure!
AdamS
March 23, 2026 at 5:07 pm
The capacitor king strikes again! Another excellent repair.
Parasuraman S
March 23, 2026 at 8:51 pm
Ha! Ha! I have sharpened my sword very well for the next war! Many thanks for your comments!
MP
March 24, 2026 at 2:46 pm
You teach how systems work and also give lots of hints on repairs, its quite commendable. It fills me with an urge to gather old boards (sounds odd and looks horrible though helpful indeed) just to study a variety of electronic circuit arrangements. Thank you.
Parasuraman S
March 24, 2026 at 5:16 pm
Glad to know that the articles are found very useful! Knowledge is something that will increase multifold when you impart it to others; the more you give, the more it will increase within. This is a universal law of nature! Many thanks for your comments!