HW-5400

[Multi-Volti Devices]

Hello:

HW-5400 has a tendency towards distorted audio on SSB...I don't remember if
the problem occurs on cw.

Heath remade the PA board due to a supposed manufacturing error using a
thinner gauge of copper foil than spec'ed.
The service department when I was there in the early  nineties was
rebuilding PA modules routinely to eliminate the question of PC foil
thickness, but when it was observed that some rigs still had a problem, it
was eventually found that rf gets in the cable between the power supply and
the rig. If you  are using a non-heath power supply (most people do not ,
but it's helpful to consider the question), this may not apply.

The Heath PS has a speaker in it...rf goes back up the audio cable to the
audio output stage, and passes by the synthesizer circuitry by virtue of the
cable harness routing...once the rf gets in the synthesizer, it 'pollutes'
everything, rx and tx.

Bypass caps, etc helped little. The synthesizer is extremely sensitive to
this. A helpful fix was to pick at the cable harness and extract the audio
cable (RG-174 if I remember) over the entire length and reroute it (I can't
remember if it's long enough or if you have to replace it with more RG-174)
as far as possible away from the synthesizer boards.

One guy (this might be an SB-1400 story) was not running a power supply ,
but a car battery in the basement (to save money), with a LONG cable (20-25
feet) to the rig...he had some serious problems, and I assumed he had a
normal power supply...that's why I mentioned this early on...you never know
what's out there.

Murray

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