Hi Guys,
To-day I just discovered something that is specific to the old EICO Model 717
electronic keyer---but it just *could* be applicable to any other gear in your
possession that utilizes a field coil / reed relay to accomplish rapid circuit
switching...
Anyway, FWIW---delete if uninterested...
I found that the keying characteristics of the internal audio oscillator in
this vintage tube-type keyer followed that of the mechanical keying mechanism
very well: however, the external device being keyed displayed a noticeably
truncated first dit---almost a contact bounce effect. The circuitry of the 717
in this application utilizes an ultra-miniature reed relay to key one's
rig---the relay is located right in the middle of a field coil that activates
it.
I found with my keyer that the location of the relay inside the coil was
haphazard, at best---plenty of room to "float"---and so I experimented with
moving the relay through the length of the coil, to see what effect, if any,
this might have on the make of the first dit. I found that (obviously) moving
the relay too far OUT of the field coil stopped the keying process entirely.
However, moving it too far INTO the coil merely exaggerated the "bounce"
effect...
I finally located the relay so that about 1/4" of it extended OUTSIDE of the
field coil itself---and I'm very happy to proclaim that the keying is perfect
now.
Previous to this "discovery", I had swapped & subbed tube after tube n the
circuit, with various degrees of success. In hindsight, I can see now that any
"good" or "bad" effects were most likely induced by the relay/coil moving
fore/aft of one another during the process of my removing the keyer from its
enclosure!
To guard against any future such variables, I applied two blobs of silicone
sealant to the coil, bonding each end to the chassis...hopefully this will
forever preserve "...the sweet spot" of the location betwixt these two
components...
~73~ de Eddy VE3CUI - VE3XZ
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