RF Modulators

Discussions around the satellite system and video distribution.
russellhltn
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RF Modulators

Postby russellhltn » Mon Sep 10, 2012 12:24 am

RussellHltn wrote:Speaking of 1U black modulators, I've seen two different brands used. On the last renovation, they installed something like a "Pico" brand. Of the 6 we had, all but one died with a bad hum in the audio. They've since been replaced with (I think) Blonder-Tongue. If I'm not mistaken, Blonder-Tongue is one of the "big boys" in the CATV business so hopefully they will hold up.


I posted that 5 years ago. Now I've had my first Blonder-Tongue fail with the same problem - a loud hum in the audio and a "hum bar" in the video. Poping the cover I see the main filter cap is bulging. Kinda unusual for a 60Hz non-switching power supply. I may decide to fix it myself. See if I can find a higher quality part.
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Mikerowaved
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Postby Mikerowaved » Mon Sep 10, 2012 1:54 am

RussellHltn wrote:I posted that 5 years ago. Now I've had my first Blonder-Tongue fail with the same problem - a loud hum in the audio and a "hum bar" in the video. Poping the cover I see the main filter cap is bulging. Kinda unusual for a 60Hz non-switching power supply. I may decide to fix it myself. See if I can find a higher quality part.

Not all that unusual to have caps on linear supplies go bad too. Without it, you'll definitely get a high 120Hz ripple on the DC supply, which (as you noticed) will manifest itself on both the audio and video signals. It shouldn't be too hard to find a suitable replacement. Probably have better specs than the old one, such as a lower and more stable ESR.
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