[AMRadio] DX-100B, output falls off gradually

[Gary Schafer]

Rick,

Check to see if there is a jumper wire on the accessory (8 pin socket) on
the back plugged into pin 1 to ground. 

The plate switch is a double pole switch. One side turns on the plate power
and the other side grounds the cathode of the vfo and buffer amp in the AM
mode when going into tx. A wire runs from that junction to pin 1 of the
socket on the back of the rig for remote keying. (Check the schematic to be
sure it is pin 1)

If that line remains grounded when the plate switch is turned off then you
will get the symptom that you describe. Checking the voltage at that pin
should go to zero on transmit and something positive when the plate switch
is turned off. 

73
Gary  K4FMX


> -----Original Message-----
> From: amradio-bounces at mailman.qth.net [mailto:amradio-
> bounces at mailman.qth.net] On Behalf Of Gary Schafer
> Sent: Saturday, November 19, 2011 8:15 PM
> To: 'Discussion of AM Radio in the Amateur Service'
> Subject: Re: [AMRadio] DX-100B, output falls off gradually
> 
> A better question might be "were any of the power supply filter
> capacitors
> changed to greater values than the originals"?
> 
> 73
> Gary  K4FMX
> 
> > -----Original Message-----
> > From: amradio-bounces at mailman.qth.net [mailto:amradio-
> > bounces at mailman.qth.net] On Behalf Of L L bahr
> > Sent: Saturday, November 19, 2011 7:45 PM
> > To: Discussion of AM Radio in the Amateur Service
> > Subject: Re: [AMRadio] DX-100B, output falls off gradually
> >
> > Would you think maybe the energy stored in the filter caps and choke
> > might have something to do with this?
> >
> > Lee, w0vt
> >
> > ----- Original Message -----
> > From: "Rick Poole" <wa1rkt at arrl.net>
> > To: amradio at mailman.qth.net
> > Sent: Saturday, November 19, 2011 2:15:01 PM
> > Subject: [AMRadio] DX-100B, output falls off gradually
> >
> >
> > Well, this is interesting...  Running some tests on my DX-100B into a
> > monitor scope and dummy load, I find that in AM mode, when I turn off
> > the Plate switch, the RF output as shown on the scope falls off
> > gradually over a period of about 1 second rather than dropping
> > immediately.
> >
> > Obviously, after I get my TR relay built and in line and hook up the
> > receiver, it's not going to be good if the TR relay drops out while
> > output power is still falling.
> >
> > Any idea what causes this?  Is this a known problem with a known fix?
> >
> > Rick WA1RKT
> >
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