[BC] Re: BE plate transformer

[Xmitters@aol.com]

In a message dated 5/3/05 12:02:23 AM Central Daylight Time, 
broadcast-request at radiolists.net writes:

<< Has anyone on the list experienced similar problems with these 
transformers?
 Is this likely a bizarre coincidence?  Or...is there some other probable
 source that is causing these failures?
 
 Thanks in advance.
 
 Gary Peterson, K?CX >>


Gary:

I have not had that particular experience but in addition to Tom O's 
suggestion, I would look at the rest of your transmitter parameters. Your plate 
current in particular. I know that might sound stupid because one would think that 
the plate overload would trip if it was high enough to kill your plate 
transformer. Verify that the plate supply is not overloaded. 

This would be a good time to be sure that your overload protection is 
actually working. Maybe there was an intermittent failure that drew lots of plate 
current and the transmitter failed to trip off. Make sure that the AC service to 
the transmitter is properly fused, etc. Is the plate circuit breaker on the 
transmitter functioning properly? Did someone bypass it because of an 
unexplained failure and then forgot to hook it back up? The plate O/L on my 20H3 here 
failed once. Transmitter sat there pulling lots of plate current and failed to 
shut off. Fortunately, I caught it in time before the plate transformer failed. 

Be sure that the proper taps are connected on all three plate transformer 
phases. Was the new transformer connected properly? Rule out any failures that 
may have resulted from improper connections. Did someone hook up the new one 
just like the old one, without verifying that both the new and old transformer 
are actually identical? Don't assume anything. Verify!

Give the transmitter a good visual inspection to see if there are any signs 
of arcover anyplace.

If you don't find anything obvious, you might call Peter Dahl, the great 
transformer guru, and see if he has seen this before. I have been doing this work 
for almost 30 years now and have never had a plate transformer failure in that 
whole time. I would say that this problem as you have described it is far 
from coincidental. 

There is either a major problem with the incoming AC or there is a concealed 
problem with the transmitter itself. In almost all of the stations I have 
worked however, the transmitter overloads and interlocks were bypassed upon my 
arrival! That's the first thing I check when taking a new job :-) Verify that 
nothing has been bypassed on your transmitter.

It is important to verify that the fault protection system in your 
transmitter is working and working properly.

Jeff Glass
WNIU WNIJ