Servicing Two Valve Radios
I received two Valve Radios from a customer, with the complaint ‘No sound’. One was GEC and another UMS. Very sorry that I do not have the latest picture of UMS, as I forgot to click it. What I have put here is an old snap taken a few years back in my very old mobile. (Both of these Radios had come to me for service a few years back in a totally bad condition, having bought from a scrap dealer.
I had to do a lot of work to bring these two to working condition then!)
I opened UMS and found a burnt resistor on the output transformer and found the primary of the transformer was open. In order to ensure that all else was ok, I connected an output transformer, which I always keep in stock for testing purposes. The Radio worked very well. Since the transformer has to go for rewinding, I kept this set aside and opened the GEC. Surprisingly and coincidently, that was the same problem in that set too! Removed it. Checked GEC also similarly using the testing output transformer and found the Radio to be working very well, the output of EZ80 Rectifier valve was not that good.
Got back the transformers rewound after a week and refit them. Both Radios performed very well. Unfortunately, I forgot to click further snaps of these two lovely Radios. GEC service was already covered by me in yet another article published long back.
Jobs completed, but not to my full satisfaction, as this customer did not want to spend money on complete refurbishing.
This article was prepared for you by Parasuraman Subramanian from India. He is 68 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/servicing-yamaha-amp-ax-530/
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vince
December 4, 2017 at 9:03 pm
if the output transformer is open best to change the Grid coupling Capacitor as if leaky cause high current through transformer ,and back to having open circuit transformer very soon
i change this capacitor when ever i work on valve radio as cheap part that can sve whole lot of trouble
Parasuraman
December 5, 2017 at 10:39 am
That was already done in the first service. The cap was rechecked and found to be OK. The fact that both TX failed indicates poor workmanship when these were rewound.
Albert van Bemmelen
December 5, 2017 at 4:21 am
Great job Parasuraman. And a fantastic engineer at the transformer repair centre. A repair service that I think simply doesn't exist in my country.
Humberto
December 5, 2017 at 1:04 pm
Good repair anyway. You are a Master.
suranag Electronics
December 5, 2017 at 2:11 pm
Very good job Mr.Parasuraman
however You are Expert for Audio Repairs.
James
December 5, 2017 at 6:16 pm
You Da Man yo'' 🙂
Yogesh Panchal
December 6, 2017 at 9:54 pm
Good job Sir,
OSCAR
February 10, 2018 at 11:33 pm
thanks i never knew that that problem can affect the audio but now i know thanks so much
Muhammad Ashfaq
February 19, 2018 at 5:25 pm
wow sir its amazing an old technique i see after a long time.