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ND-25 Problem

Posted: Thu Feb 13, 2020 3:56 pm
by dd92251
I've been asked to look at a dead Nautel ND-25...It's not putting out any RF yet appears to be OK otherwise. I haven't been to the site yet, I'm just looking for ideas on what might be a cause for its problem... so I know where to start.

The unit doesn't have any warning lites on it, ...but the PA Modules, I'm told, have flashing lites on all of them. Their fan motors can be heard working but no RF output.

I'm wondering if one of the 240 Volt phases may be out... .or possibly an Interlock is open from the Antenna Controller.

This isn't a rig that I have close familiarity with, so a little direction from someone who knows the rig is appreciated.

Thanks ...
Best Wishes
Dave Dybas

Re: ND-25 Problem

Posted: Fri Feb 14, 2020 7:54 am
by BroadcastDoc
Almost sounds like a drive or a controller issue.

Re: ND-25 Problem

Posted: Fri Feb 14, 2020 8:12 am
Never worked on one myself, but a wild thought comes to there a "FAIL SAFE CONNECTION" that mutes the rig when control path is lost"? If that opens, it might mute the RF.

The flashing lights, however could could indicate what Doc mentioned as a place to look.


Re: ND-25 Problem

Posted: Fri Feb 14, 2020 10:08 am
by rfn
Sounds all too familiar. Had to deal with an ND25 with similar symptoms a couple of years ago. It traced to a power bus having burned up in the rack with the major power transformer. It's in a difficult to reach location which allows it to escape notice when doing the annual tightening down of all connections. Nautel no longer had a replacement and though one could be fabricated at great cost and a long lead time. We were able to have one fabricated from copper service entrance cable (I vaguely remember it being 4/0) with crimped AND soldered lugs on both ends. I never liked the patchwork and a year or so later replaced the whole thing with an NX25.

One more problem with the ND25: Check the rack with the L/C combiner network. When we took the ND25 out of operation and were disassembling it found several broken connections to many of the coils. Seems fan vibration over 20+ years was to blame.

Re: ND-25 Problem

Posted: Fri Feb 14, 2020 10:30 am
by sallen
A good person to talk to at Nautel is Steve Braley, he did the floor test on a lot of ND series transmitters. He floor tested an ND50 I work on. He is a good source of knowledge on the ND transmitter. If you call the Nautel customer support number they can have Steve contact you.

Re: ND-25 Problem

Posted: Fri Feb 14, 2020 12:05 pm
by Dale H. Cook
sallen wrote: Fri Feb 14, 2020 10:30 amA good person to talk to at Nautel is Steve Braley
I'll second that. Steve is the go-to guy in tech support for the ND and XL series transmitters, and perhaps the only person left in Nautel support who has substantial hands-on experience with those series.