Forty years ago, installing a color TV set by hand opened your eyes (Part 2)

Tech 2023-06-20 09:14:18 Source: Network

Author: Dai ZhongqunHello radio electronics enthusiasts! In the previous episode, I talked about how 40 years ago I personally installed a Venus C37-401 14 inch color TV. Actually, there was a lot of effort involved in assembling and debugging a color TV! Let me talk about it today

Author: Dai Zhongqun

Hello radio electronics enthusiasts! In the previous episode, I talked about how 40 years ago I personally installed a Venus C37-401 14 inch color TV. Actually, there was a lot of effort involved in assembling and debugging a color TV! Let me talk about it today.

The author of this article first installed the Venus C37-401 14 inch color TV 40 years ago, and now everything is watching normally.

In 1983, after preparing the complete set of materials, before assembly, I repeatedly read the two books "Color TV" purchased from the service department of Shanghai TV Factory that year. I read them carefully and repeatedly, mastered the essentials, and achieved a clear understanding.

The author of this article repeatedly and carefully read the two books' Color Television 'back then.

The color TV to be assembled consists of a total of 496 components, which are officially assembled according to the circuit diagram of the Venus C37-401 14 inch color TV and the finished printed circuit board purchased from the service department of Shanghai TV Factory 1.

Some of these components are substandard, in order to ensure a "first shot" At that time, I tested these 496 components one by one, confirmed them to be correct, and then welded them one by one. Among them:

171 various capacitors;

189 various resistors;

39 various coil transformers

29 other devices

The author of this article reminisces about the hardships and fun of welding assembly back then.

Finally, it was successfully assembled by welding for 7 days and nights.

After the assembly was successful, in order to be foolproof, I carefully read the "Maintenance Manual" of the 14 inch Golden Star color TV purchased from the service department of Shanghai TV Factory that year

The author of this article carefully read the "Maintenance Manual" of the 14 inch C37-401 Golden Star color TV purchased from the service department of Shanghai TV Factory at that time.

According to the discussion on TV adjustment in the Maintenance Manual, turn on the machine for coarse adjustment, fine adjustment and general adjustment. When the test card broadcast by the TV station is clearly received (it was 11pm at that time, the TV program was finished, and Mengshan Launch pad only broadcast the test card)

After a burst of excitement, I saw that only black and white images could be displayed. I looked up relevant information and estimated that the fault was in the decoding circuit.

The next day, I moved this color TV to the power supply bureau laboratory not far away and used an SR-8 oscilloscope to measure the signal waveforms at TP301 and TP501, all of which were normal.

After returning home, I looked at the relevant chapters in the book "Color TV" and estimated that the fault was in the peripheral circuit of the decoding circuit integrated block TA7193.

After careful investigation, it was found that there may be a problem with the D305 diode in the reverse trip trigger circuit. Using a multimeter, it was found that D305 had a breakdown and short circuit,

After replacing a new diode of the same model and confirming that there is no error, once the power is turned on, "Yau Yat Tsuen will be bright in the dark", there is a color test card broadcast by the TV station (it has already passed the TV station's program broadcast period when the pilot is tested), the scene is really "all smiles after the three armies", and my heart is even sweeter than honey, let alone more excited!

The color test card broadcasted by the TV station as shown in the picture was received after troubleshooting the decoding circuit that year.

The author of this article reflects on the joyful mood after receiving the signal that year.

Of course, in the process of use, there were various situations, such as "the soldiers came to block, the water came to cover the earth", and "climbing the slope and crossing the barrier" There are still many things to discuss, so I will explain them to my friends in detail next time. Thank you!

(Copyright statement: This article is an original work by the author. The text and images in the article may not be reproduced or cited without the author's consent)

June 20, 2023

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