[Amps] Protecting the tubes!

Tue May 13 10:32:20 EDT 2003

Traian, the TS-850 transverter output goes to the "IF OUT" jack (RCA phone
jack).  To enable the transverter, the internal cable to the jack gets
replugged - this of course disables the IF OUT capability.  When the
transverter relay is picked by applying 12V thru an RFC to the IF OUT jack,
the Kenwood's output pre-driver is switched by the relay to the IF OUT jack.

I will be connecting the Kenwood's normal high power output to the RECEIVE
side of the Harris T/R relay. So... when the transverter is OFF (barefoot),
the 100W output flows thru the Harris coax relay to the antenna.  I
interlock the transverter enabling with the Harris HV on line.

In either case, in receive the TS-850 "listens" via the Harris T/R relay.

So, even if there is some failure in the Kenwood... the only place the
Kenwood 100W PA goes is to the RX side of the Harris coax relay.

I hope to document my connection scheme & a slight mod I made to the Harris
power control on my home pages in a few days.

73, Bill
~~~~~~~~~~~~~~~~
Bill Coleman    N2BC
http://home.stny.rr.com/n2bc
----- Original Message -----
From: "Traian" <yo9fzs at office.deck.ro>
To: <amps at contesting.com>
Sent: Monday, May 12, 2003 9:17 AM
Subject: Re: [Amps] Protecting the tubes!

> Hi all,
>
> The screen voltages for drivers and finals is derived from the +500V
> 8122 drivers anode voltage and is stabilised using power zener string.
> So, if the drivers anode voltage fail, no problem for their screens.
>
> RF-110A include also various protections including anode RF voltage
> sampling, (dependant of  load), anode finals current, output both peak
> and average forward power, output reflected power, air flow,
> PS overheating and interlock.
> It include its own output power limiting and protection feedback system
> (PPC and APC, a sort of internal ALC) which act to the drivers bias
> (and can be used also with  an external exciter), and even a protection
> for the case of arc discharge inside the tubes.
> If properly aligned, the RF-110A should not have problems, unless
> internal component failure or missalignment will occur.
>
> The output power limiting feedback system can be adapted for use
> with the TS850 by using an external adapter/level converter which to make
> the conversion from the RF-110A PPC output signal to the needed ALC
> level for the 850.
> These signal levels and their action are stated in the respective manuals.
> (RF-110A PPC output signal is positive, ALC needed is negative).
> For this must to experiment.
>
> Anyway, when I used TS850 for the RF-110A, I choose not to use
> the 850's transverter out but to use a power attenuator.
> The 850 is switched to the transverter state by applying an external
> voltage to one of its jacks. The low level output is available at the
> same SO239 output jack as the normal full power.
> So, if this external switching voltage is missing, a full 100W instead
> the 30mW out will be applied to the load (i.e. 8122 grids)...
> This is of great concern for the grids, not the 100mW level, no matter
> if the anode or screen voltages are on or off!
> And this because Kenwood choose to be cheaper with the separate
> low level output $1 cost jack...
>
>
> 73,
> Traian
>
>
>
> 2 wrote:
>
> > >Thanks Rich
> > >
> > >There is indeed a termination resistor - before the blocking cap there
is a
> > >.22uH coil to a 56 ohm resistor to ground.  The input is quite flat
from 160
> > >through 10M according to my analyzer.
> > >
> > >So... does that load protect the tubes & nullify the need to interlock
> > >application of RF drive?
> >
> > **  the 8122s' 2w control grids should be able to do without an
> > interlock.  How are the 8w screen grids protected from excessive current
> > caused by too-light loading, from reverse screen current, and from loss
> > of anode-V?
> >
> > >----- Original Message -----
> > >From: "2" <2 at vc.net>
> > >To: "Bill Coleman N2BC" <n2bc at stny.rr.com>; "AMPS"
<amps at contesting.com>
> > >Sent: Friday, May 09, 2003 9:38 AM
> > >Subject: Re: [Amps] Protecting the tubes!
> > >
> > >
> > >>
> > >>
> > >> >I am in the early stages of lashing together a Harris RF-110 amp.
It runs
> > >> >a pair of 8122s in class A driving a pair of 4CX1500Bs.  I am
driving it
> > >> >with the transverter output of my Kenwood TS-850, about 20 to 30 mW.
> > >> >
> > >> >I'm sure that when mated to the proper Harris exciter, there is
> > >fool-proof
> > >> >interlocking between the exciter and the amp - i.e. applying drive
> > >without
> > >> >HV.    I haven't yet found a convenient way to do this with the
Kenwood.
> > >> >There are a couple possibilities, but they involve feeding some
signals
> > >> >out of the amp & if you know the innards of this thing, additional
output
> > >> >lines will be at least a small challenge because of the physical
layout of
> > >> >things.
> > >> >
> > >> >Anyway - to the real question:  Am I worried about a non-problem?
If I
> > >> >apply 20 or 30mW drive to the 8122s without plate or screen voltage,
will
> > >> >they be damaged?
> > >>
> > >> **  In Class A, there is no grid-current, so all of the exciter power
> > >> flows into the grid terminating resistor.  If there is no 50-ohm grid
> > >> termination, your radio will likely be in a state of vexation.
> > >>
> > >> > The input is untuned and unswitched, fed directly to
> > >> >the grids of the 8122s thru a .01uF cap.  Looking at the datasheet
for the
> > >> >8122, the control grid appears to be pretty tough
> > >>
> > >> **  as I recall, the rated control grid dissipation is 2w max and the
> > >> screen is 8w.
> > >>
> > >> >- but grid dissipation
> > >> >per se is not specified.  I can't imagine a couple volts of RF doing
any
> > >> >damage.  WATSA?
> > >> >
> > >> >By the way - this is a pretty nifty box.  20mW in, 1000W out, brick
on the
> > >> >key, no tune-up, etc etc.
> > >> >
> > >> >Thanks!   73, Bill
> >
> > -  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
> > www.vcnet.com/measures.
> > end
> >
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