[AMRadio] Re: Need ID Help for 1930's Transmitter

Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Wed Sep 13 13:59:03 EDT 2006

Tubes like the 75th and 100th sometimes had caps
on the grid, the modulators in my 30k1 had caps
for the grids.

I suspect they were supposed to have caps but they
were 'extra' from eimac?

I would have to dig in the books to find a circuit
for a single ended? triode final, then look at the components
power/voltage rating on the RF deck, tube base types, filament
voltage, etc, to see what was likely used.

Looking in the OLD handbooks, there were loads of 
tubes I never saw or heard of, and they were not 
listed in newer handbooks.


> -----Original Message-----
> From: amradio-bounces at mailman.qth.net 
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of A.R.S. - W5AMI
> Sent: Wednesday, September 13, 2006 1:16 PM
> To: Discussion of AM Radio in the Amateur Service
> Cc: Glowbugs
> Subject: [AMRadio] Re: Need ID Help for 1930's Transmitter
> On 9/12/06, Don Merz <n3rht at yahoo.com> wrote:
> > The final deck has a socket for a single tube with the
> > large, twist-lock base and 2 plate-cap-size
> > connections for plate and grid caps. Not many tubes
> > fit that description, so I am thinking maybe an 810
> > goes there? The Eimac tubes are out because they used
> > a pin for the grid--not a full-size plate cap. The
> > final deck has a filament transformer (I haven't
> Don,
> Determine the filament voltage.  Also, was the bias supply for the
> final in the power supply section that's missing?  If not, what does
> the voltage appear to be on it?  This would help narrow down a final
> tube.  The Eimac tubes above the 250T (450 up) used the standard .5"
> grid and plate caps.  The 450T had both the pin and a .5" cap on the
> grid.  GE also made some Eimac like triodes such as the GE806 which
> was a close cousin to the 250T only it had .5" caps on the grid and
> plate.  Of course there are other possibilities like Taylor, etc.
> Brian / w5ami
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