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

[Chris Miller]

That is what I was thinking initially, but it seems to be there with the amp 
in full bypass.  Also it seems to disappear if the amp is removed from the 
circuit with a barrel connector.  Supply is separate and the whole system 
was working fine with the previous rig at the original station.  One caveat 
is the original rig blew up from a loss of regulation for the 13 volts stage 
(ft-1000mp).  That was my first thought that maybe the control system change 
with the new rig may have introduced weird behavior or that the failure may 
have cooked something related to the automatic band change interface.

I have tried it on two bands with the same result at the original station. 
I will have to record the audio and play it back to myself on the dummy load 
to judge off air, but I believe it is there ( hard to judge with your own 
voice in your head and the return audio in a headset at the same time :-D ) 
I think we tried it on a dummy load at the original station as well, but my 
memory fades.  One thing I noticed originally is that the Pa section seemed 
to 'talk' with modulation, that is something sounded a lot like  a modulated 
arc.  on arrival here I seemed to have a loss of sensitivity through the 
unit and it traced to tone of the BNC connectors on the tuner stage, but it 
still was giving that raspy audio after.

It is my plan to scope the bias and mains at the connector and see if there 
is something that may be slipping past my meter.

The RF audio sound was my attempt to describe that raspyness that audio can 
develop when rf is entering into your rig via the mic circuit.  It is not 
ridiculously bad but it seems to be the closest description that seems to 
best fit.
Maybe I should figure out a way to post a number of sample audio tracks if 
my description is still not the best match.

Chris

--------------------------------------------------
From: "Gary K9GS" <garyk9gs at wi.rr.com>
Sent: Tuesday, April 30, 2013 10:57 PM
To: <amps at contesting.com>
Subject: Re: [Amps] odd problem with Yaesu Quadra vl-1000 amp

> Hello Chris,
>
> It sounds like RF is coupling into the supply leads.  I'm not at all 
> familiar with the Quadra amp.  Does it use a separate supply?
>
> I'm not sure what "RF Audio Sound" is describing.  Does this happen with 
> both an antenna and into a dummy load?  Does this happen on every band or 
> only one/certain ones?  Another thought is a regulation problem with the 
> power supply.
>
>
> On 4/30/2013 9:17 PM, Chris Miller wrote:
>> 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
>>
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>
> -- 
>
>
> 73,
>
> Gary K9GS
>
> Greater Milwaukee DX Association: http://www.gmdxa.org
> Society of Midwest Contesters: http://www.w9smc.com
> CW Ops #1032   http://www.cwops.org
>
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