Desk Caller ID Telephone Repaired- MODEL: GEEPAS GTP7212
I received this desk Teflon by compliant that the hum voice is in the earphone. First I connect the telephone to the line and that was true, the hum was excite in ear phone.
I replace the hand set of earphone and microphone with another good and trusted one but still hum was present there and this indicated that the problem was inside the machine.
From old days the hum in the CRT and any audio machine was because of bad filter parts of the power supply (PSU). And was due to dirty DC voltages. When I was repairing such machines the first job was to replace the big bad capacitor from PSU by a good one and that was all. This was the first time I was trying to open this model of desk telephone but there was no big capacitor inside. The first component that I found in the telephone PCB that directly was connected to the line was a diode shape component with the part number of P6KE200A.
By testing the poles of this diode the meter did not show anything and the diode was completely open so I Googled the code and I found out that this is a special component for protection of sensitive electronic machine against any momentarily spikes and or very high unwanted frequencies that may produce in the line of transmissions. This component act also as a fuse. Since this device did not answer to my meters I decided to replace it with fresh one after replacement the hum on earphone disappears. And telephone returned to services again.
You can click on the photo below to access the information of the diode:
This article was prepared for you by Mr Beh from Iran.
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Robert Calk Jr.
December 14, 2018 at 12:43 pm
Good job, Beh.
beh
December 15, 2018 at 12:54 pm
You are welcome Robert.
Parasuraman S
December 14, 2018 at 1:22 pm
Excellent! This is a part that I have never handled.
beh
December 15, 2018 at 12:56 pm
Parasuraman thanks for supports.
Albert van Bemmelen
December 14, 2018 at 3:42 pm
Nice repair Beh. If I remember it well the same component happened to be bad in one of my monitor power adapters. After replacement also that one was fixed again.
beh
December 15, 2018 at 1:08 pm
Albert thank you so much .but let me tell you that before i install the fresh TVS diodes to circulate i test them all with multi meter but still no answer from the meter .any way i installed the diode on theboard and the result was good the hum disappeared . i searched the web to find a way to test these kind of components but could not found any .
Albert van Bemmelen
December 16, 2018 at 4:14 am
Just use the terrific DY294 tester Beh! My P6KE150 unidirection (one direction only) did perfectly limit the voltage to about 150V when inserted between Emitter and Collector of the meter and tested on DC 1000V scale. In the other direction the display shows only 000 Volts.
So just use the DY294 which also limits the current while testing and so saves the Diode from destroying at Avalanche currents. A standard DMM only can show if the diode is a defective shorting diode.
Robert Calk Jr.
December 16, 2018 at 5:33 pm
That is what I found out Albert when I got readings on my bad TVS diodes. Thanks for letting us know that we can check them with our DY294's. After studying the datasheets more, I figured that an insulation tester might check the TVS. But these 0402 TVS's are so tiny I decided not to try and test them with them. I guess I need to build some probes especially for my DY294 so I can test tiny SMD's.
beh
December 16, 2018 at 7:55 pm
Thanks Albert.
Robert Calk Jr.
December 16, 2018 at 7:32 am
None of my meters will test one either. I found a couple of bad 0402 bi-directional TVS diodes in a Kindle a while back because it did show a reading with my VOM. The new ones that I bought #LXES15AAA1-133 show no readings with any of my meters.
beh
December 17, 2018 at 12:48 pm
Hi Robert
I recommend you to get one of these DY tester .is cheap but is a great tester in our job.
cheers
beh
Robert Calk Jr.
December 17, 2018 at 8:37 pm
I do have one, Beh. I have had it for a long time.
beh
December 18, 2018 at 9:38 am
GOOD to know this.
Mihai
December 15, 2018 at 2:14 am
Hello Mr. Beh ! Thanks for sharing your experience with us !
beh
December 15, 2018 at 1:10 pm
Mihai
You are most welcome .
Mark
December 15, 2018 at 1:40 pm
Hey Beh,
Well done on your repair.
beh
December 16, 2018 at 10:20 am
MARK
I am happy you find this report useful .you are welcome .
beh
Yogesh Panchal
December 17, 2018 at 12:20 am
Good job! Beh
beh
December 17, 2018 at 3:47 pm
You are welcome Yogesh.