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-   -   troubleshoot uhf dropout (http://forum.tvfool.com/showthread.php?t=15147)

devidog 31-Dec-2014 2:23 PM

troubleshoot uhf dropout
 
I have recently installed a db8, y-10713, and rca preamp-1 with a rotator on a mast. It worked well but now drops out all uhf signals periodicaly. Thinking it was probably a bad connection I replaced the wire from the pre-amp to the db8 balun with new wire and compression fittings. It still drops out and I have figured out that if I bump the rotator 1 time and then back the picture comes back. How can I determine what part is causing the issue. It seems to me that either the balun or the amp has to be the problem. I can replace the amp off of a ladder but the balun will require bringing down the mast. I assume the balun is available from antennas direct and the pre-amp is only $22.00. I've read that these pre-amps can break at the connection if you overtighten? I don't think I did but I did use a wrench. I don't mess with the rotator much just use it to fine tune the signal for my weakest channel. The wire from amp to balun is taped to the mast above the rotor with a fairly large loop then taped again below the pre-amp. I figured this would eliminate issues when turning the antenna. Any opinions ?

Jake V 31-Dec-2014 5:49 PM

Without a TV Fool report no one can comment. I'd post the report, note what direction the antenna(s) are aimed, and then list the stations you are getting and not getting.

Have you tried bypassing the amp? What happens? If your signal strength is not great you'd loose channels but you should have some consistency on those that you do get. Is the amp on both VHF and UHF or just UHF? How far from the antenna is the amp?

I've not seen baluns fail the way you describe (but I'm not an expert). They sell for a few bucks at places like Home Depot. Very easy to replace.

devidog 31-Dec-2014 6:08 PM

Quote:

Originally Posted by Jake V (Post 48481)
Without a TV Fool report no one can comment. I'd post the report, note what direction the antenna(s) are aimed, and then list the stations you are getting and not getting.

Have you tried bypassing the amp? What happens? If your signal strength is not great you'd loose channels but you should have some consistency on those that you do get. Is the amp on both VHF and UHF or just UHF? How far from the antenna is the amp?

I've not seen baluns fail the way you describe (but I'm not an expert). They sell for a few bucks at places like Home Depot. Very easy to replace.

It's like a bad connection, doesn't affect the vhf signal just the uhf. Just moving the antenna 1 bump west then back one bump north to the same position brings it back. No I didn't bypass the amp. The balun on the db8 isn't standard at all and would only be available from the manufacturer. The tvfool report has nothing to play here as the signal is gone from all uhf channels then back on all uhf channels. If it were just 1 channel it would be different. As I stated the only thing I've tried is to replace the wire and connectors from the balun to the amp which requires me to lower the mast. I will probably just replace the pre-amp because I can do that from an extension ladder. The other question you asked is where the pre-amp is. It is on the mast about 5 feet down from the db8 and about a foot below the vhf antenna.

Jake V 31-Dec-2014 8:08 PM

If it affects only the UHF and not the VHF, and comes and goes with movement of the antenna using the rotor, and the amplifier is located below the rotor (and is stationary), then it seems likely that there might be an intermittent connection somewhere between the antenna and the UHF input of the amplifier. I'd check the connections at the antenna and the amplifier and even replace the coax before buying anything.

devidog 31-Dec-2014 9:16 PM

Quote:

Originally Posted by Jake V (Post 48487)
If it affects only the UHF and not the VHF, and comes and goes with movement of the antenna using the rotor, and the amplifier is located below the rotor (and is stationary), then it seems likely that there might be an intermittent connection somewhere between the antenna and the UHF input of the amplifier. I'd check the connections at the antenna and the amplifier and even replace the coax before buying anything.

Read my entire post... I replaced the wire and connectors from the uhf balun to the rca pre-amp. Nothing changed.

Jake V 31-Dec-2014 9:18 PM

Sorry. Missed it. Then if your new wire and compression fittings are OK, then your only next steps are the balun and the amplifier.

devidog 31-Dec-2014 10:12 PM

Thanks for the reply. I'm just looking for a more analytical solution. I'll get a pre-amp and replace it. If that don't work I'll take the mast down and replace the balun. Just seems like there should be a way to check things out and not be a "parts chaser".

Stereocraig 2-Jan-2015 11:23 AM

Quote:

Originally Posted by devidog (Post 48493)
Thanks for the reply. I'm just looking for a more analytical solution. I'll get a pre-amp and replace it. If that don't work I'll take the mast down and replace the balun. Just seems like there should be a way to check things out and not be a "parts chaser".

Other than testing for shorts and/ or continuity on cables, the equipment to give "analytical" solutions, can be a bit on the pricey side.

Common schmoes like me, are pretty much relegated to being "Parts Chasers".

This does in fact, sound like one of the connectors on one of the circuit boards may have become loose.

Some RG6 is not very cold climate friendly and can create additional stress on the fittings, from stiffness.

rickbb 2-Jan-2015 2:18 PM

Try removing the pre amp completely and see what happens.

Are the drop outs on close/strong stations or far away/weak ones? etc.

To do this analytically start with a known good setup. One TV, straight short cable run, then add one thing at a time. When it fails, that is/may be the problem.

This was recommended to me by a member and solved my pre-amp issue.

devidog 2-Jan-2015 2:40 PM

Quote:

Originally Posted by rickbb (Post 48519)
Try removing the pre amp completely and see what happens.

Are the drop outs on close/strong stations or far away/weak ones? etc.

To do this analytically start with a known good setup. One TV, straight short cable run, then add one thing at a time. When it fails, that is/may be the problem.

This was recommended to me by a member and solved my pre-amp issue.

All uhf stations drop out ... all vhf stations stay ... without pre-amp I don't get the uhf stations anyway. It's obviously one or the other, balun or amp so for $22 I'm going to pick up another rca preamp and install it next time I go to the farm. If I didn't have to take the mast down to change the balun I'd do that too. I would have to contact Antennas Direct to get one, but I don't think that's a problem, they have a facility here in the St.Louis area. I've read a lot of comments on people overtightening the connections and breaking the rca tvpreamp. I did tighten with a wrench so there's a possibile failure.

rickbb 2-Jan-2015 4:56 PM

I had the same preamp, my whole OTA is new, just installed it all this week, it worked for great for about 4 to 5 hours. Then the same thing happened, no UHF at all, just the one VHF. (Which oddly I was not getting at all with the preamp.)

When I removed the preamp completely, all the channels came back including the VHF channel. I actually got more without the preamp.

I'm guessing it's the preamp, if the balun was broken you wouldn't be getting VHF, IMHO.

I'd be hesitant to try another RCA, that's 2 with the same exact symptoms. Doesn't mean much other than a coincidence, but still.

You can get a CM7778 or CM7777 on Amazon, more pricey than the RCA, but maybe there is something going on with the RCA's?

devidog 2-Jan-2015 7:04 PM

Quote:

Originally Posted by rickbb (Post 48529)
I had the same preamp, my whole OTA is new, just installed it all this week, it worked for great for about 4 to 5 hours. Then the same thing happened, no UHF at all, just the one VHF. (Which oddly I was not getting at all with the preamp.)

When I removed the preamp completely, all the channels came back including the VHF channel. I actually got more without the preamp.

I'm guessing it's the preamp, if the balun was broken you wouldn't be getting VHF, IMHO.

I'd be hesitant to try another RCA, that's 2 with the same exact symptoms. Doesn't mean much other than a coincidence, but still.

You can get a CM7778 or CM7777 on Amazon, more pricey than the RCA, but maybe there is something going on with the RCA's?

Two separate antennas, db8 for uhf with rotor... y10713 mounted directly to the mast. I'm out on the fringe of reception and get no uhf without the amp.

rickbb 2-Jan-2015 7:26 PM

Quote:

Originally Posted by devidog (Post 48532)
Two separate antennas, db8 for uhf with rotor... y10713 mounted directly to the mast. I'm out on the fringe of reception and get no uhf without the amp.

Ah yes, makes sense and matches your original post, (now that I've gone back and read it again. :o ).

My vote goes to the preamp being bad.


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