How 10“ Wired Video Intercom System Doorbell With Camera And Monitor Plus Memory Door Security System TABA Is Repaired model: TVD-1035
Installation purpose of this machine is to open the door of a property automatically when client is outside and wants to enter in and the person behind the monitor can see and talk and after approval by pushing a button opens the door. Machine has also this ability to take a photo of person behind the door and save the photo in the memory plus date and time of request for entrance for further references. I received this machine with no sign of life….completely dead.
After opening I found inside three PCB. 1. PSU
Mostly with conventional parts and with just one out put 15 volts 1 Amp but multi read zero volts on output of psu.
- Mother board
- Display board assembly for lcd and cpu By looking at solder side of mother board and power supply I found many bad and cold joints that I resoldered again all of them but no progress after turning On the machine. My first experiment was by inserting the 15 volt DC 1 Amp with external power supply to motherboard wanted to see if two other boards are turning on separate from their own power supply or not ? Fortunately machine turned on and also the memory of machine started to display the photo of clients that took and saved them. This experiment also was useful to estimate how much machine is damaged? And answered to these questions, is LCD still is good or not and how much would be the total cost of this repair? Is it worth to spent money and time for this or not? Compare to price of a new set I received positive answers. By repairing the psu the machine will work again (I have mention that display board is receiving voltages from mother board not from psu directly) then I started to find problem in psu.
I test the transformer of power supply by BLUE RINGS first of all before any other components that I found it very good, full glowing all LEDs. Since such transformers are not available much and also not in the web either and if I find one is very expensive and make the repairer job not economical also the code numbers on this transformer was erased. That is why I test these transformers before all other parts in such smps power supplies. If transformer is not good the repair of such board will not economical.
By testing the voltages of psu I just could read 310 volts Dc on the pins of big cap this means all parts behind this point must be good. But no more voltages from this point forward to the downstream.
By using of ohm meter and other test equipment I try to find the other bad components, by experience in such small smps most problematic parts are electrolytic caps that are getting open or their value are changing or getting very high ESR. I started to check electro caps first and I found a bad cap 47micro@50v that was completely opened. Second components that are making problems are ¼ watt resistors that getting open and or their values getting very high in my case I found one five band resistor that must be 1500 ohm by reading color bands but was changed to 10000 ohm. That was the supply voltage to three pin TL431 IC (adjustable precision shunt voltage regulator). This IC controls and regulate the voltages for IC STRA6053M (this is a switching power supply IC) the supply voltages are reaching to this IC via an opto 2501, and mentioned opened electro cap
By replacing the bad five band resistors and bad cap the PSU started to work again and produced the 15 volts in output terminal and display board start to work. But this was not the end after turning on the display I noticed that the touch screen of lcd does not work and has no reaction at all, as I told before this board was consist of only smc (surface mount component’s) ICs, Diodes, Caps, and Crystal ….. And by putting the
display board of machine under the digital microscope and LED Monitor that gives me the images of joints and component up to x4000 time. I found many bad cold joints that are not visible by naked eyes on pcb and by help of hot air gun with 450 degree Celsius and very low velocity of air I resoldered all bad joints and problem of touch screen also solved.
The cost of this repair was just few American cents.
Consuming time was: 1 hour.
The price of such machine with above abilities is between 100-180 USD in the market.
This article was prepared for you by Mr Beh from Iran
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Note: You can check his previous article on Day/Night Switch Sensor Light Repair (With Hand Drawn Schematic Diagram)
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Abigail Karonga
July 1, 2022 at 11:53 am
Greetings Beh
This article shows that you are not only a good technician but also a good Mentor in the field of electronics, Some of us would have simply abandoned this repair somehow but you persevered until the gadget was resurrected Well done and great job.
Albert van Bemmelen
July 1, 2022 at 12:28 pm
Very well explained and nicely detailed repair Beh! And a successful one in no time was time well spent! I guess that the TVD-1035 display on the Taba intercom doorbell is black & white only, although the screen looks kind of bluish in the photo? Thanks for sharing!
Parasuraman S
July 1, 2022 at 3:48 pm
Excellent article and useful tips! I liked the way you mentioned the temperature of the Hot Blower. That is a good tip, indeed! Many, many thanks for your article!
Waleed Rishmawi
July 1, 2022 at 4:17 pm
i like the details in your article and it is fun to read all that information you have provided us with. keep up the good work and have a blessed day
Paris Azis
July 1, 2022 at 4:29 pm
Good job Beh! Interesting repair and well presented!
beh
July 2, 2022 at 3:53 pm
Hi to All
Thank you so much of your encouraging words and supports.
cheers
beh
Yogesh Panchal
July 3, 2022 at 11:58 pm
Beh,
Welcome! to the Group.
You have followed very practical approach for investigate the problematic area by connecting external supply & checked whether rest of the stage working properly or not before spending time for repair this will gives clear idea still how long you have to go.
Once you understand the fundamental working of Power supply Circuit you will troubleshoot it easily & this circuit Tracing is possible in single layer PCB; in multilayered PCB it is very difficult to Trace the Circuit without Diagram like any motherboard where components are on both the side.
Now repairing any motherboard is very difficult without Microscope a must have tool.
Thanks! for sharing your experience.
Abraham Egede
July 6, 2022 at 2:15 am
Thank you very much Beh,the presentation is excellent, job explicit, and approach amazing.
Keep it up please.