Re: Ubitx microphony

Bob Lunsford <nocrud222@...>

The usual method to locate a microphonic device problem area
is to use a small stiff non-metalic brush and sweep the board in
small passes and this tends to show the general area. Then I have
used a drinking straw and tapped lightly the components in that
general area. In a way, a microphonic problem is the easy one to
fix because locating the problem does not require diagnostics of
any electronic circuits with a 'scope, etc.

Some components can be microphonic but all things considered,
I would guess it's a bad solder joint. Suspect this first. If you see
some joints with a magnifying glass that look "frosty" or granular,
touch them with the tip of a hot soldering iron AFTER turning off
the power, of course. This usually is the fix for a bad joint. Some
bad joints are hard to detect, though.

Bad solder joints are not all that uncommon. On the BitX boards,
considering that they are flow soldered, suspect the wires connected
to the board first. However, don't forget the components on the front

Please let us know what you find. This falls in the unique list of what
can be wrong with a radio.

Bob — KK5R


On Thu, 12/20/18, Peter Russell <peter.russell@...> wrote:

Subject: Re: [BITX20] Ubitx microphony
Date: Thursday, December 20, 2018, 11:00 AM

When I say "microphony"
I mean that the circuit boards are acting as a
microphone - any slight tap on the case can be
heard loudly in the phones.
I haven't
tried it on transmit yet, so I don't know whether it
will be a
problem there also.
I'm sure I've seen reference to it
somewhere but I'm not sure where.
ideas will be welcome.

Peter. G8FWY

On 20/12/2018 15:05, iz oos
> What do you mean exactly with
'bit' of microphone? If you refer to low
> average SSB output, I replaced to add
another resistor (47ohm)in
> parallel to
R63 and worked nicely. However late November Barry Underwood

> suggested to use a VOGAD. So I have
just made (I still need to test it)
another external box with that compressor to use also with
other SSB
> QRPs, like ILER. I have a
mil surplus radio that use the VOGAD and I
> have always been impressed by it, as you
can just whisper and have a lot
> of
output. See the attached file made by Barry.
> Il 20/dic/2018 12:35, "Peter
Russell" <peter.russell@...

> <mailto:peter.russell@...>>
ha scritto:
Hello from a newbie!
>    I've
just completed the build of my uBITX and I have to say,
>    impressed!
>    Just one little niggle - and I'm
sure I've seen it mentioned
somewhere but I can't remember where - I seem to have a
bit of
>    microphony. Can anyone
point me in the right direction?
>    Peter, G8FWY.
>    ---
>    This email has been checked for
viruses by AVG.


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