Hello,
I didnt' see my post make it the first time (maybe I deleted it by accident).
I had a QSK switch from MFJ (PIN diode T/R switch). It had a bulb fuse in it
and it blew eventually. The guy at Ameritron told me to replace it with a bulb
from a christmas tree. Sure enough it worked like gangbusters and when the
VSWR climbed the bulb began to glow. I have a huge inventory of spares that
can be replenished off christmas season at garage sales or in christmas season
at K-mart or wallmart.
Regards,
ETC(SW/AW) Mike Kendall USN.....IT9/KE6CVH
"Joe Subich, W4TV" <k4ik@subich.com> wrote:
As one who helped Doc Sheller design and build the DEO-1500
back in the early 80's ...
> I own a DEO QSK-1500 and a previous owner wired a bulb in
> series with the fuse. When the QSK-1500 is presented with
> a SWR higher than what it wants to see the bulb begins to
> glow.
The DEO-1500 "fuse" is a standard light bulb - Chicago Miniature
#12. Other than lightning or operator error the only reason
it should blow is if the transceiver is generating RF before
the unit is switched into transmit. The QSK-1500 was designed
to be connected between the keyer and the transceiver "Key In"
jack so that it could switch the amplifier at the same time the
key was closed. This generally allowed even the slowest amplifier
relays to get settled before the QSK transceivers of the day
produced any RF.
If you are relying on the PTT output from a transceiver (even
the solid state output from the modern transceivers) to drive
the QSK-1500 (or QSK amplifier), you will blow fuse lamps.
If the fuse lamp glows with high SWR, one of three things is
happening: 1) the feedline impedance is greater than 150 Ohms
(3:1 SWR), 2) at least one of the pin diodes D3, D4, D5 are
shorted, or 3) the 500 volt supply is not right. Of course,
the 3:1 SWR must be derated if you are running "smoke" .
> The bulb is mounted on top of the unit so it is easy to see.
> I believe the bulb is a #47.
This is unnecessary. I have not refreshed my memory as to the
characteristics of the #12 and similar lamps and can't say how
much additional loss the #47 is creating on receive.
> Can these guys be popping fuses because the QSK switch
> doesn't see a match?
Fuse popping is almost always due to failure to run the keyer
through the switch (I believe the Alpha also has loop through
for a key/keyer) or lightning. Years ago the info we had put
the unknown fuse lamp failures in the 2 to 3% area. The other
failures were about half and half operator error (improper hook
up or running the amp into the wrong antenna) and lightning.
73,
... Joe, W4TV (ex K4IK)
PS. I still have one copy of the QSK-1500 service manual and
my design notes for a version that was intended to be used
with the R4C/T4XC. Unfortunately, transceivers replaced
the C-lines far too soon.
>
> At 01:49 PM 07/14/2005, you wrote:
> >ke6cvh@yahoo.com wrote:
> >
> > > I blew the PIN diode fuse.
> >
> >This is strange. I had an 86 for a couple of years, used it a lot --
> >always full QSK at at least 1300 watts output on all bands, and NEVER
> >blew the fuse. Yet some guys have continual problems with this.
> >Something is going on that isn't clear to me.
> >
> >--
> >73,
> >Vic, K2VCO
> >Fresno CA
> >http://www.qsl.net/k2vco
>
> John and Susan Bohnovic
> (954) 432-1467 voice
> (954) 431-7751 fax/data
> curlhead@bellsouth.net (she)
> bohnovic@bellsouth.net (he)
>
>
> _______________________________________________
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> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
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