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.
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 repair article below:
https://jestineyong.com/servicing-12-volt-smps-adapter/
(65)Dislikes
(0)
17 Comments
Leave a Reply
Robert Calk Jr.
June 28, 2018 at 5:27 pm
Good job, Parasuraman. You can use an ammeter instead of the series lightbulb tool. I use the ammeter in my Isolation Transformer.
I am glad that your back is well now!
Congratulations on your new appointment! I'm sure that you will make a great teacher. I doubt that tube (valve) devices will dominate the audio market, they use too much power. Tube Amps are the favorite of most musicians.
Parasuraman
June 29, 2018 at 11:00 am
Ammeter will not shift the load to itself when current is overdrawn. Rather it does not serve as a protector. But bulb will! That's the difference. If we use an Ammeter without a series bulb, before even we can read the Ampere, damages would have taken place!
Robert Calk Jr.
June 30, 2018 at 12:02 am
No, you don't just give it full power! You slowly turn the voltage up while watching the ammeter. If the current tries to climb too fast or it rises to high at low voltage, you can pretty much bet that there is a short somewhere.
I explained how I do it in my, "Camera Battery Charger Repaired" articles.
Parasuraman S
July 1, 2018 at 9:07 am
That's making the trouble shoot more complicated, as we need a variac connected and feed voltages slowly. But Bulb is the best method, which is common and easy to do, as explained by Jestine Yong in his famous books on repair. I find it easier.
Robert Calk Jr.
July 2, 2018 at 5:04 am
Yes, the lightbulb tool is the best way for most people but sometimes difficult to use, especially on tiny boards. Using the ammeter is the easiest way. And nobody should be working on live devices without going through an Isolation Transformer.
Mr. Yong mentions using the A/C ammeter in his great book, "Troubleshooting and Repairing Switch Mode Power Supplies", on page 100; and in detail starting at page 195.
As for me personally, I can plug a device into my Isolation Transformer and find out if there is a short somewhere in just a few seconds, before opening the device up or anything.
Andrew F. ali
June 28, 2018 at 9:13 pm
Nice work, Sir.
Mark
June 28, 2018 at 9:18 pm
Well done Parasuraman!
Another professional job. I hope your classes go well for you. I wish I could go as I am sure I would learn a lot!
Suranga Electronics
June 29, 2018 at 12:39 am
Good Repair Mr. Parasuraman.
albert van bemmelen
June 29, 2018 at 12:43 am
Parasuraman, you'll do great in conducting classes on Valve Radios and Amplifiers! But I doubt that the old tubes will make a comeback. That is why no doubt Fets and Mosfets are invented. I hoped that the suspense was more about some kind of useful repair invention you may have discovered. Nevertheless I am sure that you are the right man for the task!
Parasuraman
June 29, 2018 at 11:04 am
You seem to have some Sherlock Holmes instinct! Yes, indeed it was originally about some achievement or milestone reached in service. But unfortunately due to a stupid miscalculation from my side, the announcement has to find a day much later! Which means, you may have to remain in suspense for some more weeks, perhaps!(LOL)
Parasuraman S
July 1, 2018 at 9:09 am
Regarding your doubt on valve tubes coming back, kindly visit this site: https://www.pinterest.com/pin/304626362289871343/sent/?sfo=1&sender=595108675669029140&invite_code=4ae6cc2c1a7b4a099004b7c60228e857
Debirt Maynard
June 29, 2018 at 6:40 am
Excellent job as usual.
moshe jacobson
June 29, 2018 at 9:03 am
Always a pleasure to read your posts!
Paul
June 29, 2018 at 4:59 pm
Thank you sir for your technical knowledge.please sir is it possble to replace Ecap of 16v 100uf with 15v 1000uf.
Parasuraman S
July 1, 2018 at 9:12 am
No. The value should be same or at least nearest. Voltages can slightly be higher, preferably, if not slightly less. It all depends where the capacitor is used. Power supply path or signal path.
Yogesh Panchal
June 29, 2018 at 10:40 pm
Good Job! Sir
ulises Aguilar pazzani
December 24, 2018 at 10:59 am
good for You Mi Friend