[Amps] Internal QSK-5

[Kim Elmore]

I looked at the manuals available Ameritron site. I can't find a 
schematic, but simply by looking at the parts list, it's clear that 
these two switches are different. How different remains a mystery. 
I'll compare installation notes and see if I can deduce anything significant.

73,

Kim Elmore, N5OP

At 10:12 PM 1/31/2009, Joe Subich, W4TV wrote:

> > Recently, though, I had some 160 m antenna
> > problems under high power and blew the fuse lamps that protect the rx
> > PIN diodes.
>
>Wrong ... the fuse lamps protect the transceiver if the "receive"
>PIN diodes or HV power supply fails and amplifier RF gets through.
>They are also there to prevent the amplifier from running away in
>the event of a diode/HV failure.
>
> > I'll check the schematic, but does anyone have an idea or two about
> > what might be going on?
>
>Check D2, D3, D4 and D11.  Also make sure that the high voltage is
>present on L6 in transmit.  Flashing of the fuse lamps indicates
>that RF is getting back from the output of the amplifier to the
>transceiver.  D2/D3/D4/D11 should be reverse biased (through Q3)
>in transmit and forward biased (through D6 and Q4) in receive.
>
>If you had a high SWR or arcing situation, I would expect D4 and
>D11 to short and significantly impair the isolation between the
>antenna (amplifier output!) and transceiver during transmit!
>
>In the QSK-5, D1 is the normally open path from transceiver
>to the amplifier input (drive).  D2/D3/D4/D11 is the normally
>closed (amplifier bypass) path between the transceiver and the
>antenna, and D7-D10 are the normally open path from the amplifier
>output to the antenna (RF Out).
>
>73,
>
>    ... Joe, W4TV
>
>
>
>
> > -----Original Message-----
> > From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]
> > On Behalf Of Kim Elmore
> > Sent: Saturday, January 31, 2009 8:55 PM
> > To: amps
> > Subject: [Amps] Internal QSK-5
> >
> >
> > I have an AL80A with an internal QSK 5 switch (one of the early ones)
> > that I've had since new (S/N 095). For well over 20 years, it's been
> > working flawlessly. Recently, though, I had some 160 m antenna
> > problems under high power and blew the fuse lamps that protect the rx
> > PIN diodes. Blowing these is no biggie as it's happened before when I
> > mis-selected an antenna or has a switch set wrong. I replace them and
> > go on my merry way.
> >
> > WIth K3LR's help, may 160 m antenna seems to be going again. So, as a
> > final smoke test, I stated testing it under high power. But, this time
> > I'm seeing the fuse lamps light up when I transmit with more that a
> > few hundred watts on 160 m into a dummy load. I don't see this on 80 m
> > or any of the higher frequencies. As far as I know, this is new,
> > though I've never had much of a 160 m antenna and so didn't use the
> > amp it much down there.
> >
> > I'll check the schematic, but does anyone have an idea or two about
> > what might be going on?
> >
> > 73,
> >
> > Kim Elmore, N5OP
> >
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