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Old 23-Nov-2015, 12:24 AM   #25
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,569
Simply disconnect the coax lead from the amp and measure between the shield and the center conductor of the coax. Anything between 12 and 18 volts is expected.
That is a little tricky to do with the end of the coax coming up from the power inserter that connects to the preamp. You have to connect one voltmeter probe to the coax shield and touch the other probe to the center conductor without shorting it to the shield. I sometimes insert the cable connector into an F81 adapter and insert a short length of 18 gauge bare copper wire into the other end of the F81. The 18 gauge wire is the same size as the center conductor of the RG6 coax. The attachments show me checking the voltage at the lower end of the coax when the preamp (old model 7777) is powered.

Do you have the new model 7777 with only one antenna input?

Troubleshooting the new 7777:

It appears my channel master 7777 quit working?
What makes you think it is bad?
If my cable wires cross from my preamp will this do?
Please explain what you mean by that.

Can you receive anything on either antenna without the 7777?
Attached Images
File Type: jpg F81snip.JPG (69.9 KB, 293 views)
File Type: jpg 0747test2a_1.jpg (98.7 KB, 286 views)
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 23-Nov-2015 at 11:18 AM.
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