[TenTec] RE: Omni V Fm'ing

[Robert & Linda McGraw K4TAX]

I still say it is still a connector problem which no one has seemed to
explore.

Regulation in a PSU is the result of an abundance of fast slew rate gain in
the regulator circuit.  In fact, a fast dynamic regulator (not a 723 type
device either) does not need a filter capacitor at all, as it will follow
the fluctuations of the AC ripple, much faster than a dynamic load of speech
or CW keying.

There is no problem with the design of the Tentec 962 power supply.  It
works up to 22 amps and does not cause a problem with the Omni or Paragon
series radios.  Now, is there a fault in the PSU such as one of the series
pass transistors, Q1 or Q2, open (not a typical failure mode), or no drive
to the base or an emitter resistor (R3...R6) open and  etc. That's another
problem.

One problem that I discovered with my Omni VI+ was the fuse holder was
broken at the threads on the inside of the radio.  The fuse had inadequate
contact pressure and thus higher in-circuit resistance.  Replaced the fuse
holder.........problem solved.

73

Bob K4TAX


----- Original Message -----
From: "MW0CDO" <gw7lhi@hotmail.com>
To: <VE1BN@aol.com>
Cc: "Ten-Tec List" <tentec@contesting.com>
Sent: Wednesday, March 27, 2002 1:02 PM
Subject: Re: [TenTec] RE: Omni V Fm'ing


> Hi Don.
>
> Thanks for the info.
>
> The PSU has 33000uF reservoir already, and all other radios tried on the
> supply work fine.
>
> I'm going to check out the internal wiring etc. of the TT radio and if
> nothing found a car battery will be tried.
>
> Paul MW0CDO
> ----- Original Message -----
> From: <VE1BN@aol.com>
> To: <gw7lhi@hotmail.com>
> Sent: Wednesday, March 27, 2002 1:36 PM
> Subject: Re: [TenTec] RE: Omni V Fm'ing
>
>
> > Hello Paul -
> >
> > Perhaps you need a much larger filter capacitor in your PS to increase
its
> > dynamic stability.
> >
> > Many (not all) PS today are a bit "undercapt" with the result the steady
> > no-load voltage output will drop instantaneously (and relatively deeply)
> at
> > the start of a CW or SSB load for a few milliseconds, then recover.  It
is
> > quite noticeable on an oscilloscope looking at the output voltage.
> Remember
> > these drops are only at the instantaneous starting of a load and are
very
> > short.  Probably enough of a drop to vary the voltage on a sensitive
> circuit
> > to cause the "FM-ing" you are plagued with.
> >
> > I found by adding capacity, a large one for the 12-15 volts high current
> PS
> > needed by today's rigs, the voltage will not have this effect, and
remains
> > steady.  My homemade regulated PS have a minimum cap of 30,000 uF.
> >
> > Steady state voltage under load (minimum change from load to no load) is
> > really a problem with insufficient capability of the power transformer
or
> the
> > general dynamics of the PS.  If the output voltage droops too far, then
> the
> > transformer is to be blamed.   But - this is not what would cause your
> > "FM-ing".  Just another thought (ha).
> >
> > Hope this will give you some food for thought, and will be of help.
Good
> > luck.
> >
> > 73 -
> >
> > Don     ve1bn@aol.com
> >
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>