[BC] BT-20-A

[Dana Puopolo]

Yu are partly correct. Te driver tube in this transmitter was a 6076.
The PA tubes  were 5671's.

-D

------ Original Message ------
Received: Fri, 30 Mar 2007 05:43:23 PM EDT
From: nakayle at gmail.com
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Subject: Re: [BC] BT-20-A

Hmmm, I don't think so.
Wasn't the driver a 4CX5000?   The PA was a 6697.

 - Nat


On 3/30/07, Dana  Puopolo <dpuopolo at usa.net> wrote:
> It was a 6697 driver tube, not a PA tube.
>
> And I was the man....
>
> -D
>
> ------ Original Message ------
> Received: Fri, 30 Mar 2007 05:17:37 PM EDT
> From: nakayle at gmail.com
> To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
> Subject: Re: [BC] BT-20-A
>
> I assume this was part of "5K1".   I don't recall this happening with
> our 50H which was similar but we did have a lot of problems with 5K1
> and it's various trip and reset coils.  But the 50H did have levers
> that shorted the 15-KV bus whenever a PA door was open.  The most
> dangerous part of that transmitter was the capacitor bank.  Power dips
> would often blow one or more of the fuse-wires on the HV caps.  There
> were spring loaded plungers on each that were suppose to short the cap
> if the wire broke but they often didn't work.  First thing I always
> did when I opened the rect cubicle was ground each of those caps with
> the stick- and very often I got a arc that sounded like a shotgun
> going off.  And you had better keep a ground on them while you
> replaced the fusewire because those suckers would build back up a
> charge just from 'memory' effect.
>
> -Nat Kayle
>
>
> On 3/29/07, gRAdy Moates <lists at loudandclean.com> wrote:
> > Just a quick note. . .
> >
> > I saw a man come within 2 inches of dying because of a similar
> > relay on a BTA-50G 50,000 Watt transmitter.  We were trying to
> > find and fix a problem, and had cycled the transmitter completely
> > off, filaments and all.  We had been working for hours, and the
> > guy had skipped the shorting stick procedure this one time.
> >
> > He touched the control grid ring on one of the PA tubes and
> > felt a "tingle", so he grabbed the shorting stick and brushed
> > the tube with it. . .
> >
> > . . .and drew a 2" arc from the anode!!
> >
> > Even though the entire transmitter was shut down, the
> > "ReClosing Relay", which actually connected primary 480V
> > 3-phase power to the HV supply, was physically stuck in the
> > "on" position, and the tubes had full plate voltage on them!
> >
> > That relay was so unreliable, even after rebuilding by the
> > Boston GE Apparatus Service Shop, that we had to add a
> > step in the shutdown procedure in the remote control that
> > would energize the overload relay to force the ReClosing
> > Relay to open.
> >
> > Grady
> >
> >
> >
> >
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