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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You may check on his previous repair article below:
https://jestineyong.com/shorted-zener-diode-found-in-voltage-stabilizer/
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Albert van Bemmelen
December 10, 2018 at 3:20 pm
Glad to see that you managed to repair your valuable SS-2050B Vartech oscilloscope Parasuraman! Replacing all old capacitors must have been a hell of a job. I hope my (Tektronix, Philips and Russian portable) oscilloscopes won't need new replacement capacitors for a long time. But probably loosing the calibration firmware inside the Srams of my Tek's will be the main concern if they loose the Lithium battery backup voltage on their mainboards in time.
James
December 10, 2018 at 6:52 pm
There is a fungus among us. :[) LoL I learn something new every time you publish something, thanks man'.
Robert Calk Jr.
December 11, 2018 at 2:13 am
Good job, Parasuraman. I am glad that you got your scope fixed.
Christian Adzic
December 11, 2018 at 3:41 am
What a nice scope!
I like this kind of scopes.
Probably older than I am but however. 🙂
What attracted my attention to this article is the "...fungus attach...".
I'm interested in is how could the fungus live in such of hard environment like an electronic device PCB board etc.
There are many chemically components (copper, soldering paste, Zn, Pb etc. )on the PCB and that is a good area for corrosion than fungus.
I assume that scope was in a really humid environment because fungus needs a humid environment.
If there was a humid environment there should be corrosion an not fungus.
But, however, I would also investigate if that environment is safe for human living.
Several times I found fungus on electronic devices but only outside, never inside.
This is really interesting.
Thank you for this article.
My best regards.
Parasuraman S
December 11, 2018 at 9:39 am
I live in Kerala, India, which is a humid place, being a coastal state. We get good rains for almost 6 to 8 months. The Oscilloscope is placed near the window in my bedroom converted serviceroom. The dampness in that area is likely to cause fungus attack, especially when the scope is not used for many weeks.
Yes, you are right we are prone to fungus diseases, and I too had its attack a couple of times, which required long treatment. Generally our body develops resistance.
Corrosion many times is a result of its attack.
The 'attach' was a mis-spelt word for 'attack', which has subsequently been corrected.
Many thanks for your valuable comments!
pavithra
November 13, 2022 at 10:59 am
I saw this while i'm searching hv transformer details of similar kind of scope. (GW instek GOS-622G) that I received without HV transformer. i am trying to wind a transformer myself and try. so.. looking for information of transformer. EI core, 1KV output + voltage doubler to make 2KV. unknown center tap (may be 500V)
regarding the fungus attack.. This is not a fungus. it is copper oxidization. since you live in Kerala (same as here) humid and salt breeze can cause this.