[AMRadio] Re: Modulation transformer ID and repair

[Brett Gazdzinski]

I always wanted to try feedback, from something like
the mod monitor, or some sort of detector, and injecting into a low level
audio stage....

Have not tried it yet tho...

Brett
N2DTS

> -----Original Message-----
> From: amradio-admin at mailman.qth.net
> [mailto:amradio-admin at mailman.qth.net]On Behalf Of John Coleman, ARS
> WA5BXO
> Sent: Monday, December 01, 2003 1:57 PM
> To: amradio at mailman.qth.net
> Subject: RE: [AMRadio] Re: Modulation transformer ID and repair
> 
> 
> 	That's very true Bret. I got an idea about 20 years ago from RCA
> and Gates BC XMTRS diagrams.  They use direct coupled cathode 
> followers
> to drive the grids of the 833s.  Not a lot of trouble 
> considering the HV
> transistors that we have today.  The FETs and bipolar transistors have
> better characteristics for that sort of thing than the 807s they used
> back then.  I would never go to a class B or AB2 grids with out my
> transistor drivers.  
> See http://www.qsl.net/wa5bxo/driver1.html
> 
> 	I have always wanted to try the inverse feed back circuits that
> RCA and Gates used on the modulators.  But I never have.  I 
> once had the
> schematic diagram of the Gates 1KW but lost it in the flood 
> of 94.  I'm
> sure there are a lot of ways to do it I just have never taken the time
> to try. 
> 
> 	BTW I think your right. I have learned a lot more from stuff
> that didn't work out quite right.
> 	I think the most time consuming thing I ever did was to
> neutralize a single triode using an inductor from plate to grid (in
> series with a blocking cap of course. The inductor resonates 
> with the G
> - P capacitance of the tube.  Let me say "It Works very well, 
> but it is
> not my first choice for construction mechanics, plus it has 
> to be tuned
> every time you change frequency.) 
> 
> 73, 
> John, WA5BXO
> 
>   
> 
> -----Original Message-----
> From: amradio-admin at mailman.qth.net
> [mailto:amradio-admin at mailman.qth.net] On Behalf Of Brett Gazdzinski
> Sent: Sunday, November 30, 2003 9:41 PM
> To: amradio at mailman.qth.net
> Subject: RE: [AMRadio] Re: Modulation transformer ID and repair
> 
> The push pull parallel 100TH deck does take quite a bit of 
> driving power, with the losses, likely close to 20 watts,
> which is what the UTC LS grid transformer is good for.
> 
> That may be part of the problem, but class B triodes always
> seem to sound less clean than a good AB1 amp.
> 
> Brett
> N2DTS
> 
> 
> 
> 
> 
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