Fungus Attack In Vartech Oscilloscope
This Vartech Oscilloscope Model SS-5020B belongs to the writer and it was found in ‘no beam’ condition one day on switch on. As you all know, our tools and instruments are the first priority.
So, opened the set and investigated into its cause. It was not having much dirt or dust; nevertheless I cleaned it using my blower as usual.
Once we remove the top and bottom cover, we can keep the oscilloscope in upright position on its strong legs. The handle is mounted on its top cover and goes with it. The handle has lock positions. I am detailing this only for those who are yet to get their hands on one. There was fungus attack on the CRT Board and high voltage section that goes to CRT neck. The following pictures are self-explanatory.
As you can see, the fungus attack had made it watery, because of moisture formation. I thoroughly cleaned the areas using IPA and brushed it well. I also cleaned the CRT socket thoroughly and used a needle to scrape it well. The hardened solder behind (last picture above) was loosened by adding flux, and removed using wick.
Then I re-soldered it properly. As I had already done capacitor replacement on this Oscilloscope a couple of years back and had done a thorough dry solder patch up, I could not find anything else wrong. So, fit back the CRT socket and switched on. The beam re-appeared and caused a grin of satisfaction on my face!
Fit back the covers, after checking the scope left on for a few hours. It worked very well, adding the job to my satisfaction bag, unhesitatingly!
This article was prepared for you by Parasuraman Subramanian from India. He is 69 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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