‘BSF SOLDIERS’ Saved This Amigo Patient Monitor Adaptor Model YFDY-0904900
This adaptor was rushed to my ‘techie-hospital’ reporting to be dead. The adaptor was already partially opened by the biomedical technician to check and it was rushed after seeing liquid spillage and damages. Unlike in the hospital, I moved a set undergoing ‘surgery’ to a safe place and took this up on an emergency basis.
On a close inspection, I found that the MOV along with the 2.5A fuse had blown; one yellow box type and two blue X2 capacitors had got charred:
The inductor coil and the board also had black marks on it. The ring test of the SMPS transformer showed healthy indicating that there were no directly shorting components either in the primary or secondary. I cleaned the dark area with IPA and used long bristled brushes so as to reach the bottom of the coil.
I had already removed the Mosfet and double diode fixed on two heat sinks located on both sides, to enable a thorough checking of the board and to do this cleaning. As we all know the fuse and MOVs are ‘Boarder Security Force Soldiers’ which take the brunt and prevent damage to its ‘living (loving too) country and its citizens!’ I cleaned the box type capacitor and checked its value:
The 0.47uF (470nF) capacitor was showing 295.6, whereas a new one showed 456.4nF (2.89% less) which was well within the tolerance. The drastic reduction in value is a sign of shorting. So replaced the box type cap as well as the two 222K blue X2 type caps, along with the 2.5A fuse. Removed and checked the 100uF/450V and fount it to be reading 120uF which is an indication of its getting dried. Replaced that also. As a routine maintenance, I also replaced the 10uF/50V with 10uF/63V in the primary and the other three 1000uF/16V caps with 1000uF/25V caps in the secondary.
Then retouched the board thoroughly from one end to the other. There were a lot of SMD components including the switching IC. Cleaned the board thoroughly using IPA and brushed it very well. Checked and re-checked to ensure that there were no SPR-made mistakes like overlapping solder joints. It passed all my visual tests using an X10 lens. Applied power and got a healthy reading of 9.38V. Fixed the covers and fastened all sides with black tapes to camouflage the body colour. Informed the biomedical techie to arrange collection next day morning. The whole process took well over four hours of me. Mission accomplished with multiple satisfactions that got easy entry into the collection bag.
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.
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Yogesh Panchal
October 10, 2026 at 3:35 pm
Good Fix! Sir
It was wonderful to hear that the patient recovered and was discharged.
Parasuraman S
October 10, 2026 at 4:48 pm
Ha! Ha! That was a wonderful apt jokily comment! Many thanks!
Albert van Bemmelen
October 10, 2026 at 6:06 pm
That it took about 4 hours is completely understandable knowing these smps adapters are not made to be easily serviced! Thanks for sharing another power adapter repair Parasuraman.
Parasuraman S
October 11, 2026 at 1:54 pm
Many thanks for your encouraging comments, dear Albert! I love challenging chances!
Imoud.O
October 11, 2026 at 12:15 am
I wonder if IPA can damage the insulating covering of induction and transformer coil.
Parasuraman S
October 11, 2026 at 1:54 pm
It can. We need to be careful on such components. Many thanks!
Mark J
October 11, 2026 at 3:11 am
Good job on the repair Parasuraman. Sometimes those power adapters are to get open to service them. Once again good job.
Parasuraman S
October 11, 2026 at 1:55 pm
Many thanks, dear Mark! You are right there!