[TenTec] Omni VI Rubbery crud on PCB

Gary F dukeshifi at comcast.net
Tue Jul 18 08:18:02 EDT 2017

That stuff IS conformal coating!

It it put there to reduce microphonics in VCO's.

Paraffin wax would have worked as well and would not have been acidic. EE's are not chemists...


Sent from my iPad

> On Jul 17, 2017, at 9:22 PM, Bwana Bob <wb2vuf at verizon.net> wrote:
> Yuk!  I've seen brown crud on the foil side of the circuit boards  my Paragon and another one that I worked on. In those cases the crud was excess soldering flux. I cleaned it off with isopropyl alcohol and cotton swabs.  The white stuff may be some kind of oxidation or corrosion.  Mold would be black.
> 73,
> Bob WB2VUF
>> On 7/15/2017 7:32 PM, Ken Brown wrote:
>> My Omni VI had some dark brown rubbery stuff on the XTAL osc and BFO
>> printed circuit boards, It is sort of like rubber cement and reminds me of
>> similar stuff I found in Kenwood TS-440s. There is also blue green copper
>> corrosion on the edges of the rubbery crud along with with white powdery
>> stuff. I think the powdery stuff may be mold or fungus. I have spent
>> several hours on each board trying to remove it as best I can.
>> It is not on every board, and not on any of the boards in an older Omni VI.
>> I am wondering if it is something that was put there by the Ten-Tec
>> factory, or if some previous owner did it? I guess it's purpose may be to
>> dampen possible microphonics in the oscillators. It definitely caused some
>> undesirable, unintended consequences in a humid climate.
>> Has anyone else seen this in an Omni VI?
>> DE Ken N6KB
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