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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