I had two CM 7777 preamps in the attic over heat, " Im guessing" in the past 5 years. Its not the power supply or the inserter. The first CM preamp only works with the strongest UHF signals no VHF. Seconded CM preamp total failure. Reconnected the first preamp using the same power supply and inserter just to have some TV. I had them hanging from a rafter not in the insulation. House has soffit and ridge ventilation, no attic fan. Im thinking about placing the new one in the soffit hoping the, "cooler" air will stop it from over heating. I have orders not to place it in any closet. Looking for other ideas and/or better preamps. Thanks
How to keep a preamplifier cool in the attic?
- Thread starter freeisforme
- Start date
- Latest activity Latest activity:
- Replies 24
- Views 4K
Do you own the property or rent? Wondering since you said you have been 'ordered' not to put it in any closet. If you own you can install one or more solared powered attic ventilators to reduce the heat build-up. Your only cost would be the initial purchase price (plus installation if you are unable to do it yourself). After that you will enjoy the benefits of them for free as the sun will foot the bill for their operation. In addition to helping with the preamp issue they will also make it cheaper to cool your home in the summer.
Last edited:
You could put the power inserter just about anywhere... it doesn't have to be in the attic
Wife, cant take up her closet space. Good idea on the fans but im not cutting a whole in the gable ends or roof.Do you own the property or rent? Wondering since you said you have been 'ordered' not to put it in any closet. If you own you can install one or more solared powered attic ventilators to reduce the heat build-up. Your only cost would be the initial purchase price (plus installation if you are unable to do it yourself). After that you will enjoy the benefits of them for free as the sun will foot the bill for their operation. In addition to helping with the preamp issue they will also make it cheaper to cool your home in the summer.
Some ideas:
1. Buy another preamp. The 30dB 7777 was known to be less reliable.
2. Put the preamp down near the TV. Not ideal, but it might work.
3. If you have power in the attic, use a thermoelectric cooler for the preamp.
Amazon.com : thermoelectric cooler
I think you just had some bad luck, I don't think it's the heat. These things bake in the Phoenix sun and keep chugging along.
I do have power in the attic. Im thinking about the CM Amplify+ or the televes 560483. If they offer the extended warranty im getting it. I will keep the cooler in mind.
Side note rabbit73: CM still didnt update the LTE filter in the JOINTenna I never did buy it for the RF channel 2 antenna. I did buy CMs HPF 50MHZ filter, it helped some. Also got a nanaVNA for 5$ yard sale find. I trimed the antenna about an inch, that help some more but needs more. Last, the electric company did a massive upgrade of the town. Just in my immediate area they replace evey pole on the main road. Channel 2 comes in 8PM to 8AM. Im ok with that. Thanks again.
Huh? I've had a CM 7777HD for years with no issues.
Well hell. If it's out of the weather and dry why not drill a series of holes in the case for ventilation? Did you try running it without the case at all and see if that helps? If it d.oes and you're worried about critters getting in glue a chunk of fiberglass window screen to cover the holes. How hot is hot? Component failure hot? Or hot like attic temperature plus normal operating temp. hot?
Attic hot + operating temp. no critters. We did have some 95 degree weather for a few days. I thought of leaving the case off but when you take the cover off there a part that touches the case. Not sure if its a ground or using the case as a heat sink. I could drill holes in it. I didn't think of that
Never mind the last post. Your right. I could have remove the case. The parts are attached to the cover not the case. Im a dumb a@#. Some darken areas area the power input. I wounder if thats where it failed.
Attachments
It does appear to have heat sinks mounted on the back plate. So don't take that off!
If you are looking at the dark spots on those solder bumps in the second (right) image, I don't think that's indicative of a failure.
Not the same amp. CM caused a lot of trouble when they used the number 7777 for many different amps.
I like the CM7777HD Amplify. It has high and low gain: 30 and 17 dB.
The original 7777 had two antenna inputs; one for VHF and one for UHF. That was my favorite preamp.
It was replaced by a 7777 that only had one antenna input.
That is the preamp that freeisforme shows in his attic photo. Its gain was stated as 30 dB. CM received many returns. Some users had high signal levels which caused overload. Also it wasn't very reliable; it failed soon. CM changed the design to 24 dB gain, but they didn't change the printed specs.
And now there is yet another 7777:
Last edited:
Well here's a thread from way back. I saw that 7808 linear regulator. If it's dropping the 15 volt wall wart pixies down to 8 volts. Well those pixies have to go somewhere. In the form of heat. I'm pretty sure you will get some loss in a long run of coax. But short runs will definitely get almost all of the juice (and amperage) to the amp.
See where the guy dropped it to 12V? I'll bet you the regulator was cooler too.
If it were me. On my 7777 I would slap a lab supply on it and drop the voltage to where I start losing dB. But I bet if I keep it a touch above 8 volts AT the regulator.....it's gonna' work just fine. The data sheet mentions thermal protection as well as short circuit protection. That one looks kind of chinesium. If you touched it with 15 v running to the amp. Would you blister your finger? How hot is hot? Like, you power it on and it works for a few minutes and then craps out hot?
www.satelliteguys.us
See where the guy dropped it to 12V? I'll bet you the regulator was cooler too.
If it were me. On my 7777 I would slap a lab supply on it and drop the voltage to where I start losing dB. But I bet if I keep it a touch above 8 volts AT the regulator.....it's gonna' work just fine. The data sheet mentions thermal protection as well as short circuit protection. That one looks kind of chinesium. If you touched it with 15 v running to the amp. Would you blister your finger? How hot is hot? Like, you power it on and it works for a few minutes and then craps out hot?
CM-7777 Using 12Vdc Power Supply
Has anyone ever powered a CM-7777 with approximately 12Vdc instead of the provided 15Vdc power supply? Instead on reinventing the wheel I am hoping to minimize my OTA rebuild with any member's experience. The loaded voltage at the amplifier is 14.5Vdc. Using POE breakout, the loaded voltage is...
www.satelliteguys.us
