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

[Rick Poole]

At 09:01 PM 11/19/2011, Gary Schafer wrote:

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

Good evening, Gary.

There isn't a jumper, but there is continuity between pin 1 and 
ground regardless of the position of the Plate switch.  I did check 
the schematic and pin 1 is connected, through a choke, to the hot end 
of the side of the Plate switch that connects to the Phone/CW switch 
and thence to the cathodes of the VFO and buffer tubes.  So, that 
side of the Plate switch (and, the cathodes of the VFO and buffer 
tubes) are always grounded whether the Plate switch is on or not.

That explains a lot; in addition to explaining this issue, it also 
explains my other issue, that I get a "spotting" signal in the 
receiver even when I don't have spotting turned on.

When I bought this transmitter, it came with an SB-10, and I'm pretty 
sure the previous owner meant to only use it in SSB and never in 
AM.  So it looks like there is some undocumented mod made on the 
assumption that it would never be run in AM (although the previous 
owner was very good about documenting things... the manual is 
liberally marked up in many different places with lots of notes).

I'll have to get ahold of the previous owner... he has been very 
helpful to me in the last couple of weeks although he does take a 
long time (many days) to answer email.  Meanwhile I'll open 'er up 
and trace down what he did.

Thanks for the pointer, looks like you were spot on...

Rick WA1RKT