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Old 18-Dec-2016, 2:58 PM   #14
jerrymc
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Join Date: Jan 2015
Location: 92336
Posts: 30
CM-7777 Failure in COLD Temps

Quote:
Originally Posted by jerrymc View Post
OK...I'm pretty sure I found that it was in fact the balun 300 ohm crappy leads.
I barely unscrewed the first lead and it simply broke right off.

I took the balun and tested continuity between the metal fork lead and wire and it was iffy; IE: I had to press pretty hard with my VOM leads to get any reading.

So, I decided to cut and replace the end leads with the round type ones and tin and solder the wires inside, rubbed some dielectric gel on all metal, and wrapped them nicely with elect. tape.

My UHF stations are all back and it's 66F outside tonight; granted only a couple weak stations are out, but that's normal for me behind this damn mountain.

I'll wait for tomorrow's weather as we're expecting rain this weekend and possibly another thunderstorm...

THANK YOU, THANK YOU, THANK YOU, FOR EVERYONE'S HELP!
Well, I spoke too soon about the balun being bad...

When the temps dipped to below 50F, almost all channels would disappear again!

I contacted Channel Master, even though my 90 day warranty was over, and their suggestion was "signal overload."
I'm no engineer, but how in the hell can their be a good signal at 60F+ temps as opposed to signal overload at 40F?
One other thing I noted, in the evening KVCR (a local station) would also drop out COMPLETELY.

So, I ordered another $22 RCA preamp TVPRAMP1Z from Walmart.
Replaced the CM-7777 with the TVPRAMP1Z on Tuesday. VIOLA!
Not only did I get all my channels back, I now receive about 15 more!

Right now it's 36F outside and ALL CHANNELS ARE PERFECT!

While the CM-7777 was still installed, during a cool day, I aimed my thermometer at it from the upstairs bedroom and noticed the left side of the box was 10F colder than the right side, even though the sun was not shining on the box. (Maybe the warmth power on the left side?)

So my only guess is either a cold solder on the board or a bad component...?

I recently read a similar story on Amazon's reviews...

"These amps fail in cold temps, I install professionally and right now I have three for three failed. They said they fixed the problem but they did not. I will no longer use these amps." Markus Kemp, Amazon reviewer Oct 23, 2016.

Any thoughts???
__________________
HD8200XL and HDB91X with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

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