RCA-BTA1M

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RCA-BTA1M

Post by burninbob »

I work on KGRV's transmitters in Winston, Oregon. The night transmitter is an old RCA-BTA1M transmitter. In the audio feedback circuit many resitors were burnt. I replaced them with 2 meg resitors as on orig spec. The audio level is extremely low. This transmitter has been through many owners and patched together well before I was handed the old beast. Could the 807's be at fault in the first or second stage?
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Re: RCA-BTA1M

Post by Deep Thought »

Check the capacitor between the modulation transformer and reactor. If it goes very little of your audio is making it to the PA.
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Re: RCA-BTA1M

Post by ChuckG »

It's been years since I worked on one of those old RCA's, certainly swapping the audio driver tubes with known good tubes would be a start. Losing one of them will drop your audio level considerably. Has the audio distortion level increased, or is it just too low?
I don't recall if that box has cathode return resistors on the drivers or modulators, but that'd be another place to look, they are necessary to complete the audio path.
If you've lost the resistors in the feedback network there are likely others that went bad elsewhere along with them.
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Re: RCA-BTA1M

Post by burninbob »

I have found the problem, a burnt resitor hidden on the multimeter switch. It leads right to the right 1st audio stage!
Also at the same time on the 807's final bias, a 47 ohm resitor was open. After replacing both...it worked and back in business! Thanks for the input as those areas will be checked to prevent future outages!
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Re: RCA-BTA1M

Post by K9EZ »

burninbob wrote:I have found the problem, a burnt resitor hidden on the multimeter switch. It leads right to the right 1st audio stage!
Also at the same time on the 807's final bias, a 47 ohm resitor was open. After replacing both...it worked and back in business! Thanks for the input as those areas will be checked to prevent future outages!

Awww now Bob.... there is a requirement of PICTURES of said transmitter!! :D
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Re: RCA-BTA1M

Post by PaulBWalkerJr »

K9EZ wrote:
burninbob wrote:I have found the problem, a burnt resitor hidden on the multimeter switch. It leads right to the right 1st audio stage!
Also at the same time on the 807's final bias, a 47 ohm resitor was open. After replacing both...it worked and back in business! Thanks for the input as those areas will be checked to prevent future outages!

Awww now Bob.... there is a requirement of PICTURES of said transmitter!! :D
I have a few pictures of an RCA BTA1-M that finally died after something like 40 years of continuous service to one station and countless instances of jurry rigging where only one interlock, a front bottom cabinet door worked right.
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Re: RCA-BTA1M

Post by Scott.Cason »

How's this? It's the back up for WLOU in Louisville, and as you can see, still works!
RCA.jpg
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Re: RCA-BTA1M

Post by BroadcastDoc »

I can tell you right now that you'll fit right in here. :D

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Re: RCA-BTA1M

Post by Scott.Cason »

BroadcastDoc wrote:I can tell you right now that you'll fit right in here. :D

Welcome!
Thanks Doc. Jeff Welton with Nautel just told me about this place. I take care of about 8 stations on a regular basis. I have more where that came from.
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Re: RCA-BTA1M

Post by BroadcastDoc »

Scott.Cason wrote:Jeff Welton with Nautel just told me about this place.
Now usually we'd ban anyone that Jeff has invited, but we'll let it slide this time. :lol:
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Re: RCA-BTA1M

Post by ernie »

hello folks..long time lurker..had to post in this one

WRCS Ahoskie NC ..and complete with CBS labs Volumax/Audimax processing
Image
and yes..thats been their main transmitter since 1968 when they bought it new
Last edited by ernie on Tue Sep 01, 2009 7:28 am, edited 1 time in total.
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Re: RCA-BTA1M

Post by BroadcastDoc »

Thanks for sharing, Ernie!

I'll have to post some more pics of my still functioning BTA5...
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Re: RCA-BTA1M

Post by NECRAT »

Image
WBBF 1120 Buffalo's main RCA...

Image
And the backup RCA BTA-1MX
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Re: RCA-BTA1M

Post by NECRAT »

Awww. a couple more. Why not??

Image
WKBW 1520 Buffalo, NY. Working backup..

Image
WXXI 1370 Rochester, NY. Semi-Working backup... (Yes this IS the official Mr. Fybush station.)

Image
WHYN 560 in Springfield, MA.
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Re: RCA-BTA1M

Post by NECRAT »

OK This is AM Video... but....

RCA early generation TV transmitter
Image
WSYR TV 9 Syracuse, NY.
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