BE AM-6A RF Out Problem

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Deep Thought
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Re: BE AM-6A RF Out Problem

Post by Deep Thought » Tue Jul 09, 2019 3:18 pm

rfn wrote:
Sun Jul 07, 2019 7:45 pm
I have never tangled with anything BE but I did have a similar-sounding problem with a Nautel ND25. A couple of PA modules showing red indicators but all the the regular checks found no problems. Just as an experiment I swapped modules around and found the problem stayed with the slot rather than traveling with the modules.

Ultimately, and quite by accident, I got inside the combiner cabinet and found the braided wires connecting two of the coils to the circuit board had broken. I blame it on fan vibration over 20+ years of 24/7 operation. Since I found the problem while decommissioning (installing an NX25 replacement) I tacked one back on, fired it up one last time; the one associated PA module no longer had a red light. Didn't bother with the second one or check any of the others because (there being no market for it, even for parts), it was destined for the dump.
As luck would have it, I have a client looking for one of these. :(
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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kkiddkkidd
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Re: BE AM-6A RF Out Problem

Post by kkiddkkidd » Tue Jul 09, 2019 6:06 pm

dd92251 wrote:
Tue Jul 09, 2019 1:42 pm
SOLVED !!! Inside the PA Harmonic Filter / Antenna Tuning Unit of the transmitter there was a burned up wire that became disconnected. On Coil L3 there is a 1/4-20 bolt that connects three wires together, the nut wasn't real tight on this bolt and the wire lugs connected with it and the bolt/nut itself overheated. The plastic on the coil where this bolt was located melted and some of the turns on L3 also lost their insulation to heat.

This is the second BE AM-6 transmitter I've come across that has had an issue in this part of the transmitter. For whatever reason the hardware gets loose inside this area. Probably a good idea to make a maintenance check of this area if you own one of these rigs.

Thanks to everyone for their suggestions ! :D
Glad you found it.
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
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kcbooboo
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Re: BE AM-6A RF Out Problem

Post by kcbooboo » Wed Jul 10, 2019 5:50 am

As I recall, the ATU isn't the easiest unit to get into for "routine" maintenance. However if you DO get inside it, make sure the roller inductor rotating shafts are clean and lubricated with an appropriate grease so they don't jam up. Had that happen one night. Couldn't get the roller shaft out without taking a lot apart, so we ended up drilling a hole in one of the end plates to extract the shaft. That let us clean the shaft and roller bearing. Worked great after that.

Loose hardware may have come that way from the factory. Back in the 70s a company I worked for purchased computers from another factory and every one came in with loose and missing hardware to hold the front panel hinge to the chassis. Eventually I rejected the units and returned them until they got their act together. This sort of problem didn't happen in shipping the units 90 miles; they were never tightened at the factory. $#it happens.

Bob M.

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Deep Thought
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Re: BE AM-6A RF Out Problem

Post by Deep Thought » Wed Jul 10, 2019 8:40 am

kcbooboo wrote:
Wed Jul 10, 2019 5:50 am
they were never tightened at the factory. $#it happens.
Just had another case of this last week. Kintronic Labs 40 amp roller coil...outer nuts and tubing connection tight, but someone forgot to tighten the inner nuts on the slip ring connection when this coil was made:
toasty.jpg
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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