[Amps] odd problem with Yaesu Quadra vl-1000 amp

[Chris Miller]

Hi to all, 

I am attempting to help out a friend with a Yaesu Quadra VL-1000 amp that appears to be giving a weird problem after a recent radio upgrade.

When transmitting through the amp there appears to be a slight distortion of the transmitted signal such that it sounds like it has a slight rf audio sound to the voice.  When transmitting at power the rf audio sound slightly increases.  We tried changing rigs to a different models with similar results.  Also tried the amp in a different station, just in case there was some rf interference related with the first station, with similar results.  Second station has clean audio with high power so the station should be ok.  Second station is only using the manual band switching method.

Rf signal on each module looks similar and bias on each module seems good.  Carrier through amp seems good.  Looking on a Motorola comm test set there appears to be no extra spurs and  the noise either side of the carrier appears to be about 35 dB down.

Before I chase my tail some more, has anyone run across a similar description of the audio getting a slight rf sound related to this amp?  Solutions?

Thanks in advance for any help,

Chris
VE3CEA