Realistic 43-212 wireless intercom
Recently, I repaired a Realistic 43-212 wireless intercom (28 years old) for a friend, with the fault being that there is no reception on either end.
A frequency measurement from the RF input/output transformer shows that the frequency of this model is about 190 kHz when the "Talk" button is depressed.
With this information, a signal generator was attached and one of the units had distortion, while the other one produced a clean test tone.
Disconnecting C7 and C8 and applying a signal to the RF input/output transformer in the faulty unit resulted in a clear signal.
C7 and C8 (both 250VAC X-class units which couple the RF frequency to the mains wiring) were replaced (one or both units had faulty C7 and C8) with new units, and testing revealed no further problems.
One adjustment (without the need to remove the cover) is set the Squelch setting on both units on-site, because their electrical wiring is different to ours.
Note in the picture of the faulty capacitors that the epoxy/resin is flaking off one unit (with internal oxidisation) and another unit has a visible split in it (also with internal oxidisation).
This reminds me of a failure of a similar-looking capacitor at: https://www.badcaps.net/forum/showthread.php?t=3979
Maybe we should be wary of capacitors with clear epoxy or resin?
A frequency measurement from the RF input/output transformer shows that the frequency of this model is about 190 kHz when the "Talk" button is depressed.
With this information, a signal generator was attached and one of the units had distortion, while the other one produced a clean test tone.
Disconnecting C7 and C8 and applying a signal to the RF input/output transformer in the faulty unit resulted in a clear signal.
C7 and C8 (both 250VAC X-class units which couple the RF frequency to the mains wiring) were replaced (one or both units had faulty C7 and C8) with new units, and testing revealed no further problems.
One adjustment (without the need to remove the cover) is set the Squelch setting on both units on-site, because their electrical wiring is different to ours.
Note in the picture of the faulty capacitors that the epoxy/resin is flaking off one unit (with internal oxidisation) and another unit has a visible split in it (also with internal oxidisation).
This reminds me of a failure of a similar-looking capacitor at: https://www.badcaps.net/forum/showthread.php?t=3979
Maybe we should be wary of capacitors with clear epoxy or resin?
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