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@hotmail.com>
Sent: Wednesday, May 01, 2013 7:36 PM
To: <garyk9gs@wi.rr.com>
Cc: <amps@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@wi.rr.com>
Sent: Tuesday, April 30, 2013 10:57 PM
To: <amps@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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