Leaked And Rusted E-Cap Found In Sansui TV
This CRT TV was brought to me with the complaint that it has bizarre colours! What I do normally in such cases always is switching it on in front of the customer and seeing. But this was brought to me without any prior notice when I was about to go out.
When I took it up for service after a few days, I totally forgot about it and straightaway opened it for my usual cleaning and dismantling the PCB. Just see the pictures, which are self-explanatory:
I cleaned the PCB thoroughly before patching up the dry solder and finished retouching all the solder points on the board right from CRT PCB.
Like a professional barber doing a fine hair cutting job and looking for any left out, I too probed the entire PCB for any left out and ‘nipped’ it neat, clean and shining! Here is the board after finishing the retouch, before cleaning up flux.
On second thoughts, I thought of rechecking the three resistors on the RGB B+, and found these to be showing 9.90K by two and 7.45K by another. Normally, in these places the values will range between 10K-12K-15K. It cannot be 7.45K. So, what has happened here is a drop in resistance, which is very rare, but possible to find in such circuits. Removed these resistors, colour codes of which had faded beyond accurate reading.
Replaced these three resistors with 10K 2W, after scraping the burnt marks on the PCB to the extent possible. Looked for any abnormal ESR values of capacitors and found a few, one of which had got leaked and rusted underneath.
This was a 10uF/160V capacitor located near the FBT, which looked normal from the top. If I had not checked the ESR, I would not have suspected it!
Lubricated all connectors including CRT socket. After conducting a 100W bulb load test and ensuring that the B+ was 110V, disconnected and resoldered the jumper to the FBT and fit the PCB back on the CRT. Switched on through a series bulb and found it not very bright for any possible short. As the CRT TV draws high current, we have to connect it to mains directly, without use of a Bulb. Otherwise the bulb will draw power and TV will either pulsate or not switch on. Found normal raster. Connected it to a video source. Look at the lovely pictures:
Here is a picture of the TV, just to see how it looks:
Finally, the picture of the components replaced:
Incidentally, I was able to lift the CRT TV to and fro, which showed that I have fully recovered from my low back problems! A good sign of improvement! (Anyhow, I do not want to get it again!)
Another added to my satiating list!
Now to break the suspense opened in my last article:
I have been requested by a local Association to conduct classes in Valve Radios and Amplifiers and bring back the nostalgic Valve Technology. I have started preparing myself for this event, which is very exciting for me, as this is my favorite subject! It looks like the Valve might dominate the audio market in the near future!
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: