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

Thu May 2 23:53:49 EDT 2013

A little further progress, I had a chance last night to check the 48v 
supplies with the scope and all seem to be good for regulation with no sign 
of rf on the power.  Line regulation is about 3 to 4 volts of voice ripple. 
Bias seems to have nearly no ripple on modulation and is sitting at about 9 
volts before entering into the pa modules.

I took a detour after that to fix up the display lights and after that work 
was done I noticed tonight that the display lights were flickering ever so 
slightly.  It traced down to the control cable connectors between the power 
supply and the pa.  This line supplies the power to the control board, the 
display board, and also supplies the power for the ALC circuitry.  I think 
that maybe (crossing fingers) this may be the source.  Cleaned the 
connectors and placed deoxit on the contacts and things seem to be stable on 
the lights.  Bench test and on air testing, while monitoring my audio, seem 
to sound ok.  Comm test set shows the noise sidebands a little lower now, 
about -45 dB.  I am going to try a group that is familiar with the nature of 
the signal from before to see if this tagged the problem.

--------------------------------------------------
From: "Chris Miller" <c_miller_1 at hotmail.com>
Sent: Wednesday, May 01, 2013 7:36 PM
To: <garyk9gs at wi.rr.com>
Cc: <amps at contesting.com>
Subject: Re: [Amps] odd problem with Yaesu Quadra vl-1000 amp

> 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
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>> -- 
>>
>>
>> 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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