Channel Master CM 7777 Help - AVS Forum
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post #1 of 39 Old 08-06-2009, 01:16 PM - Thread Starter
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Hey all,

I ordered a Channel Master CM 7777 unit from SolidSignal.com for use on my parents house in Mississippi. Dad and I installed it on an outdoor antenna (40 ft high) putting the amp right below the rotor. Power supply of course indoors. The cable run was about 50-60 ft total. Anyway once we hooked everything up according to the directions and tried it out, all the HDTV channels that they were sort of kind of getting completely dropped out. According to Solid Signal this is what happened " Its quite possible the amp is bad. ESPECIALLY if you unplug the power supply and you still get the same amount of channels. If an amp is not working then you will get an 80% reduced signal. So even on a working amp when you unplug it you lose most of your stations. If the amp didn't work then you would get a 80% reduced signal no matter if its plugged in or not. Based on this quick test I can deem this unit defective, and get a replacement underway." So we did the test and sure enough it was the amp (or at least we think).

My question is should we continue to stick with the CM 7777 or is their another system that would be better for my parents setup? I know there are probably some details I left out but I would appreciate any thoughts on this matter...
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post #2 of 39 Old 08-06-2009, 04:32 PM
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Post your TVFool results. Either the amp is bad or overloading was the problem. This will help in answering whether or not the 7777 is right for you.
John
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post #3 of 39 Old 08-06-2009, 05:12 PM
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Are you sure you hooked it up correctly? Amp has option of separate or combined VHF and UHF antenna inputs.

Could also be a problem with DC continuity between power supply and preamp or a bad power supply. Disconnect F connector at power supply and measure voltage. Then do the same at the preamp.
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post #4 of 39 Old 08-06-2009, 07:02 PM - Thread Starter
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can't post url until three post...test 1
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post #5 of 39 Old 08-06-2009, 07:02 PM - Thread Starter
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test post 2
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post #6 of 39 Old 08-06-2009, 07:03 PM - Thread Starter
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post #7 of 39 Old 08-06-2009, 07:05 PM - Thread Starter
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We tried the amp with the combined UHF/VHF and the FM trap set to "out". We did check the power supply voltage and it was floating all over the place.
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post #8 of 39 Old 08-07-2009, 09:19 AM - Thread Starter
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So any thoughts on whether or not I am overloading the amp based on the tvfool url I posted?
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post #9 of 39 Old 08-07-2009, 10:06 AM
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Quote:
Originally Posted by msu12181 View Post

So any thoughts on whether or not I am overloading the amp based on the tvfool url I posted?

No TV overload. Did you try the FM trap set to "in"? I doubt it is the problem, but personally, I would see if it makes any difference.
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post #10 of 39 Old 08-07-2009, 11:32 AM - Thread Starter
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Yea when we first hooked the unit up, we followed the directions and left everything in its default factory setting (FM trap in, combined UHF/VHF). Seeing that this didn't work we called our local Radio Shack and they said it needed to be set to FM trap OUT. Tried that and still no luck.

We sent the unit back to SolidSignal and got a refund on the non working unit. My question is now - Do I take the chance that it was just a bad CM 7777 unit or do I need to consider another setup?
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post #11 of 39 Old 08-07-2009, 11:34 AM - Thread Starter
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By the way too, when I opened the pre amp box up to change these settings I noticed a strong odor like burnt electronics. However I didn't see any changes in the color of the solder or burn marks on the board itself.
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post #12 of 39 Old 08-07-2009, 12:28 PM
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I have a question for other cm-7777 owners:
Does the 'preamp box' (the gray metal box that is mounted on the mast) run pretty hot?
As in too hot to hold a finger, much less an entire hand, on?
(I'm guesstimating that it must be 120+ degrees F on the metal casing if I can't even hold a hand on it for longer than 5 seconds!)

Is this normal for a CM7777 that is powered up, pre-amping 2 antennas?
(One homemade 2-bay VHF, and one homemade 4-bay for UHF?)
Oh yeah, the antennas and the preamp are in an attic.
(in Southeast Minnesota, so it shouldn't be too extremely hot in the attic.)

The operation of the CM7777 has been great for me, so it doesn't appear that anything has failed internally.

Sort of along the lines of msu's prior post....

Always tweaking, modifying and re-arranging my electronics....
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post #13 of 39 Old 08-07-2009, 12:43 PM - Thread Starter
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Quote:
Originally Posted by strudel.chris View Post

I have a question for other cm-7777 owners:
Does the 'preamp box' (the gray metal box that is mounted on the mast) run pretty hot?
As in too hot to hold a finger, much less an entire hand, on?
(I'm guesstimating that it must be 120+ degrees F on the metal casing if I can't even hold a hand on it for longer than 5 seconds!)

Is this normal for a CM7777 that is powered up, pre-amping 2 antennas?
(One homemade 2-bay VHF, and one homemade 4-bay for UHF?)
Oh yeah, the antennas and the preamp are in an attic.
(in Southeast Minnesota, so it shouldn't be too extremely hot in the attic.)

The operation of the CM7777 has been great for me, so it doesn't appear that anything has failed internally.

Sort of along the lines of msu's prior post....

I noticed it was getting that way on me when we were checking it out after the initial install. The preamp box was really hot, had to have a pair of work gloves on to handle it. Of course, I was on a metal roof in South MS in the middle of July too...
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post #14 of 39 Old 08-07-2009, 12:55 PM
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Winegard has a video on youtube showing how to troubleshoot a preamp power supply. The video is for winegard preamps, but channel master preamps get power the same way except the power injector/splitter and power transformer are combined into a single unit.
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post #15 of 39 Old 08-08-2009, 06:43 AM - Thread Starter
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What do you guys think about a Winegard AP 8275 Chromstar 2000 Series VHF/UHF Pre Amplifier for my situation given the TVFool results or should I stick with the CM7777? I have yet to order anything and I read that the Winegard has a circuit layout that virtually eliminates transistor burnout.
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post #16 of 39 Old 08-10-2009, 06:04 PM
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Quote:
Originally Posted by msu12181 View Post

What do you guys think about a Winegard AP 8275 Chromstar 2000 Series VHF/UHF Pre Amplifier for my situation given the TVFool results or should I stick with the CM7777? I have yet to order anything and I read that the Winegard has a circuit layout that virtually eliminates transistor burnout.

I've never had a problem with a CM7777, except one I broke off a connector on, which was my fault. Just curious, did you notice what country your 7777 was assembled in?

The 8275 is "OK" but from your TVFool, I would stick with a lower-noise 7777.

Check all your connections and make sure it's connected like this:
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post #17 of 39 Old 08-10-2009, 06:15 PM
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Quote:
Originally Posted by Digital Rules View Post

No TV overload. Did you try the FM trap set to "in"? I doubt it is the problem, but personally, I would see if it makes any difference.

There is a strong possibility of overload from WFFF-FM on 96.7. Run fmfool from your house to see the signal strength.

The advice from the Radio Shack clerk was wrong.

FM overload is more likely to occur with a 2-69 antenna, but not so much with a 7-69 or a UHF only. There is no reason to use a 2-69 antenna unless there is a channel 2-6 within range of your house.
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post #18 of 39 Old 08-11-2009, 06:18 PM
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Quote:
Originally Posted by msu12181 View Post

I noticed it was getting that way on me when we were checking it out after the initial install. The preamp box was really hot, had to have a pair of work gloves on to handle it. Of course, I was on a metal roof in South MS in the middle of July too...

My CM7777 is cool to the touch, always. It is connected to an indoor antenna on the bedroom TV.

Bob 61231
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post #19 of 39 Old 07-18-2012, 03:07 PM
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Hello there,
I am planning to buy a CM7777.
Stumbled across on this thread from google.

Below are my TV fool results:
TV Fool Results

Do you guys think a CM7777 will help?

Thanks so much in advance. I am a complete newbie for this stuff.
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post #20 of 39 Old 07-18-2012, 03:32 PM
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Note: turrmoil is not the thread starter for this thread.
He has posted his question on an old thread because his problem is similar.

Hello, turrmoil:
Quote:
Do you guys think a CM7777 will help?
No, it will hurt because the preamp will be overloaded by WATC, which is only 1.1 mi away from you in Atlanta. Even without a preamp it might be strong enough to overload your tuner.

The only way you could use a preamp for your weak signals, if that is what you want, would be to insert a custom bandstop filter to attenuate WATC before the preamp.

What antenna are you using? Where is it located?

What channels do you want?

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post #21 of 39 Old 07-18-2012, 03:59 PM
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I have yet to receive reliable performance reviews of the new version of the CM7777. The original dual input version was one of the best reviewed consumer grade preamps available. The new single input version has a higher gain of up to 30db, but it does not apparently have the same low noise figure of 2.0. That spec is unclear and has yet to be determined. Since the classic old version is for the most part no longer available, any further 7777 discussion should focus on the new version. If PCT is using design circuitry similar to their dist amps, then it may be a decent product. But that has yet to be determined. Reviews welcome, and a comparison between the old and new versions even better.
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post #22 of 39 Old 07-18-2012, 04:06 PM
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Quote:
Originally Posted by rabbit73 View Post

Note: turrmoil is not the thread starter for this thread.
He has posted his question on an old thread because his problem is similar.
Hello, turrmoil:
Quote:
Do you guys think a CM7777 will help?
No, it will hurt because the preamp will be overloaded by WATC, which is only 1.1 mi away from you in Atlanta. Even without a preamp it might be strong enough to overload your tuner.
The only way you could use a preamp for your weak signals, if that is what you want, would be to insert a custom bandstop filter to attenuate WATC before the preamp.
What antenna are you using? Where is it located?
What channels do you want?

Thankyou Rabbit73.

Below are the details you asked:
I have a ClearStream 2 50 mile antenna... details below:
Antenna Specs on Amazon

The antenna is installed on a mast left behind by Dish Network which is about 5.5 to 6.0 ft from the ground.

I added the GE signal amplifier inside in my distribution box and it seemed to help a little... I started getting the channels listed above... earlier I was not getting these at all.
Link to amplifier I installed yesterday

After installation I started getting channels like CBS, GPB Kids, GPB Knowledge and a few more. Earlier without the signal booster even ABC and Fox5 were cutting in and out.

After installation of GE amplifier, Fox5 and ABC seem to be stable (do not cu out) but new channels I started getting do cut in and out.

What do u say?
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post #23 of 39 Old 07-18-2012, 04:18 PM
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turrmoil,

if you identify the specific stations (by either call sign or channel, not content), it will help us to figure out what's wrong. Chances are, you're having problems with WXIA (11.x) and WGTV (8.x). If so, you need to add the C2 VHF Reflector Upgrade.

As mentioned, your proximity to WATC will cause most amps to overload.
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post #24 of 39 Old 07-18-2012, 04:33 PM
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Quote:
Originally Posted by ProjectSHO89 View Post

turrmoil,
if you identify the specific stations (by either call sign or channel, not content), it will help us to figure out what's wrong. Chances are, you're having problems with WXIA (11.x) and WGTV (8.x). If so, you need to add the C2 VHF Reflector Upgrade.
As mentioned, your proximity to WATC will cause most amps to overload.

I'm having trouble with 18-1 ; 18-2 ; 18-3 ; 21-6 ; 21-7 ; WUVG

Does this help?
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post #25 of 39 Old 07-18-2012, 05:54 PM
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That GE dist amp is probably not the best choice, and as you can see, it gets poor reviews on the Home Depot site. It probably has a high noise figure and poor design circuitry. A better choice for a dist amp is the PCT/Channel Master 3414 which gets good reviews and does not overload easily. They also make one and 2 port versions. They may still have some at Fry's, although recently it looks like they've stopped carrying most Channel Master products. It can also be used as a preamp at the antenna with a remote power supply that can be purchased from pctstore.com or channelmasterstore.com. And Dow Electronics carries the CM4228HD antenna which they say works best for all Atlanta stations, including HiVHF and of course UHF. They are in Gwinnett Co right off 85 at Boggs Rd. Ask for a wholesale account to get the best price.
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post #26 of 39 Old 07-18-2012, 06:59 PM
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Quote:
I'm having trouble with 18-1 ; 18-2 ; 18-3 ; 21-6 ; 21-7 ;

There aren't any stations in the Atlanta area with those virtual channel numbers. See of you can get the call signs.

You're likely catching summertime tropo from Chattanooga.

Edit: Okay, 18.x is from Chatsworth. Rotate the antenna towards Chattanooga for that one as you're trying to receive it off the back of the C2.
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post #27 of 39 Old 07-19-2012, 08:41 AM
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Thanks tylersc and ProjectSHO89

I will preferably replace the antenna... hopefully 4228 will bring better luck... smile.gif I also plan to add CM3414. Between the two I think I should be all set.

Cheapest new 4228 I see online is $65 and $70

Will call this Dow company as well to see how much they can give it for.

Thanks all, I'll report after I have the new antenna up.
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post #28 of 39 Old 07-19-2012, 08:55 AM
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Quote:
Originally Posted by tylerSC View Post

That GE dist amp is probably not the best choice, and as you can see, it gets poor reviews on the Home Depot site. It probably has a high noise figure and poor design circuitry. A better choice for a dist amp is the PCT/Channel Master 3414 which gets good reviews and does not overload easily. They also make one and 2 port versions. They may still have some at Fry's, although recently it looks like they've stopped carrying most Channel Master products. It can also be used as a preamp at the antenna with a remote power supply that can be purchased from pctstore.com or channelmasterstore.com. And Dow Electronics carries the CM4228HD antenna which they say works best for all Atlanta stations, including HiVHF and of course UHF. They are in Gwinnett Co right off 85 at Boggs Rd. Ask for a wholesale account to get the best price.

Spoke to Dow Electronics, best price they said was $85 !!
Amazon has it for $89, couple of other sites have it for $65 and $70 as well.
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post #29 of 39 Old 07-19-2012, 06:24 PM
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Did you ask for wholesale account price? I'm thinking it was about $49. Well I would go for the $65 if you decide to get one.
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post #30 of 39 Old 07-20-2012, 10:45 AM
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Called them again today. Price is $85.
Will try the $65 place next

BTW, I am expecting to get my 3414 either today or tomorrow. Will report back if adding that on my existing setup helps.
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