{Collins} Re: 75S1 - 6BF5




George,

Years ago I tried that swap in a 75S-3 and I didn't like the audio quality.  
To me that indicated it was not a direct replacement and I used the orginal 
tube.  I suppose it could be an emergency replacement if you were out of 
6BF5s.

John WA9ZBW


>From: George J Misic <ke8rn@xxxxxxxx>
>Reply-To: ke8rn@xxxxxxxx
>To: tllind@xxxxxxxxxxxxxxxx
>CC: COLLINS@xxxxxxxxxxxxx
>Subject: {Collins} Re: 75S1 - 6BF5
>Date: Tue, 1 Jan 2002 20:04:51 -0500
>
>
> > While I was listening to the Collins New Year's Eve party, I was paging
>through some Collins Collector's monthly magazines and found an article
>on p.9 of the December, 1991 issue about replacing the hot 6BF5 with the
>more common 6AQ5A in the 75S1.  The writer stated that the filiment
>current of the 6AQ5A was only 450 mils or about 38% of the 1.2 amps
>required by the 6BF5.  Since it ran cooler it was better for the rig.
>Somewhere else, I read that one could not just plug in a 6AQ5A (as the
>first writer indicated) and run the receiver, but extensive rewiring was
>required.  Question:  Which is right?
>
>I looked both tubes up in an old copy of GE ESSENTIAL CHARACTERISTICS
>Tube Data; both tubes have the same basing [EIA base7BZ], so no rewiring
>of the base should be needed except to balance the filament current if
>the rig is operated from an external power source [12.6 or 25.2 volts].
>I assume that Collins used the 6BF5 to balance the filament current for
>12.6 or 25.2 volt operation; it is really a TV vertical deflection
>amplifier tube.
>
>I seem to remenber hearing about the base rewiring a few years back and
>never checked it out personally.  As it turns out, both tubes are based
>the same.  73 and Happy New Year.
>
>George KE8RN
>Sponsored by the Collins Collectors Association http://www.collinsradio.org
>Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
>Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
>1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
>Sun AM Net: 29.050 Mc-1200 Central
>


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Sponsored by the Collins Collectors Association http://www.collinsradio.org
Nets: Tues: 3.805 Mc-2000 Central / Thur: 3.875 Mc-2000 Central
Fri: 3.895 Mc-2000 Pacific / Sun: 14.263 Mc-2000 UTC
1st Wed (of the month) AM Net 3.880 Mc-2000 local (ET, CT, MT, PT)
Sun AM Net: 29.050 Mc-1200 Central





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