I opened a circa-2005 TV tuner VHF/UHF “can” from an 19″ CRT Emerson TV and found these hollow MELF components. Can anyone identify what they are? They measure as capacitors but I initially suspected they might be bead inductors. Please see attached photos. Note that the circuit also includes multilayer ceramic capacitors.
They didn’t appear hollow when soldered on the PCB because solder filled in the ends. However once they were desoldered I noticed some hollow ends. Inside one end of the component there is what appears to be a “plug” blocking the hole (I forced one out by pushing a lead through the open end). The ‘plug’ is round and flat like a short flat cylinder (like a hockey puck). I’m not sure of the purpose. Since these are hollow (except for the plug) I initially suspected they might be bead inductors. However my LCR measurements don’t confirm that (not confident about UNI-T readings):
2.612 nF, 0.L ohms, — mH / measured with DER EE DE-5004 LCR
2.65 nF, 0.L ohms, 6.87 mH / measued with UNI-T UT603 LCR
The tuner PCB is labeled SMEWN870A and the can had the label UTUNNTUAL025 / TEDH9-300A / 1227CT3A. I couldn’t find a schematic or datasheet.
(last image is courtesy of electronicrepairguide.com)
Reminds me of tube ceramic caps, but those went the way of the Dodo a long time ago, probably in the 80's...
Although some were adjustable, so maybe that's what the plug was for? A factory trimmed cap?... Quite dubious.
Seems like tubular ceramic caps are still being made but as 3-terminal feedthrough caps. That makes sense for filtering connectors for example.
But that doesn't really answer why they used tubular caps in your tuner when they had MLCCs available...
Answered by bobflux on December 26, 2020
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