I used to have an old Vox Continental Baroque organ from 1969, made in
Italy, with Ducati capacitors. It had a piano register and an organ
register. The thing had been through a hard life when ound it at the
thrift store, and I had to invent a new power supply and a top cover for
it to get it to work.
When I powered up the piano section, it made this multi-tone growling
noise. After a good bit of poking around, I eventually concluded that it
was due to the high-impedance, pressure-sensitive switches in the piano
keyboard. They had just enough leakage, when not pressed, to turn on
most of the notes just a little bit, all the time. It might have been
due to too many beers spilled on top of the thing in its former life.
On 2/11/16 6:22 PM, 'threeneurons' via neonixie-l wrote:
Well I'll go to the end, with the solution ... Clean your Boards !!!!
Now to the problem at hand, and its inadvertent solution. A customer
returns a board (for evaluation) on what's causing his ghosting problem. I
turn it on to confirm the problem ... yep, ghosting. Pretty severe, too. I
examine the board visually, but all the parts are in the right place, and
the solder joints look okay. So, before probing around further, I decide to
clean off the flux residue. When I'm done, I let it dry for a half hour,
before applying power. Turn it On ... no ghosting. Apparently, the flux
residue (and whatever contaminants it trapped) was conductive enough, to
turn ON, inactive "nodes" (transistors).
In conclusion, clean the flux residue off the board !
--
David Forbes, Tucson AZ
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