[BC] RE: substitute driver for tube for FM-2.5K ?

[dhultsman5@aol.com]

I have sold several  Continental 802-A and 802-B FM Exciter to users of the Gates/Harris  FM-2.5H&K transmitters.   The onlt recommendation we made was to use a BNC "T" to parallel the PA Grid input with a quarter-wave shoted coax.  This is strictly a protected in case the is a short to grid in the tube, it will protect the output transistorsof the exciter.
 
Most users agreed that the transmitter sounds better without the IPA stage being used.  One Customer originally installed the exciter and drove the IPA stage, he then found out that the exciter would drive it between 30-40 Watts easily so he removed the IPA.  He was very impressed with the sound.  
 
I have likewise sold alot of 802-A&B Exciter to users of Gates and Harris FM40H and 40K series parallel transmitters which also used the driver stage IPA from the 2.5 kW transmitter to drive the splitter to the two PA stages.
 
Dave Hultsman
Continental Electronics .
Birmingham, AL
Tel Toll Free (888) 822-1078
Fax (205) 822-6441
 
 
-----Original Message-----
From: gglaenzer at hqradio.com
To: broadcast at radiolists.net
Sent: Tue, 27 Mar 2007 10:08 AM
Subject: Re: [BC] RE: substitute driver tube for FM-2.5K ?


yes, this one does have the connector

I will keep that idea in mind

Thanks !
G


----- Original Message ----- 
From: "Tom Taggart" <tpt at eurekanet.com>
To: <broadcast at radiolists.net>
Sent: Tuesday, March 27, 2007 6:07 AM
Subject: [BC] RE: substitute driver tube for FM-2.5K ?


> The "H" and at least some of the "K"'s had a coaxial connection from the
IPA to the PA cavity.
>
> Get a good exciter with at least 30 watts of drive, pull the IPA out, and
feed the exciter directly into the PA.
>
> Works fine.
>
> Remember that Collins (later Continental) had a similar design 2.5 kw
transmitter which had no IPA.  Instead their exciter had 20 watts driving
the final.
>
> I have a 2.5 "H" that developed a short in the IPA socket.  Was blowing
the fuse on the 700 volt IPA plate supply (which also supplies screen
voltage to the final).  This happened on a weekend, of course.  At the time
I was using an MX-15 to get  1100 watts out (small Class A with a high
AHAAT).  To get something up and running I snipped & taped the plate
connection to the IPA & ran the MX directly into the PA.  Had to turn the
exciter's output down because the IPA was acting more like a buffer than an
amplifier.
>
> Now, of course, you need more drive than that to run the transmitter at
full power. The MX, at full bore, will only get you half power.  We
subsequently got a mod on this station to increase power to near equivalent
6 kw A, which required a TPO of 2450 watts. So the MX was replaced with an
802A, then a much newer BE FX-50.  About 25 watts gives me the required TPO.
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