I had the same problem with my Corsair I. Maybe the designs are
similar. See if the Delta has a Counter Logic Board for the display.
On the Corsair, this is in a shielded box along with the Counter Time
Base Board. In this design, an MK58398N is used as a preset/programmable
counter. The programming pins are 11, 12, 13, 14. They are set by a
combination of diodes, IC's and transistors to preset the counter
depending on band and USB/LSB. In my case, one of the bypass
capacitors on the preset lines was shorted, causing that line
to be pulled high all the time.
Also, the PTO signal goes through an SN7490 prescaler before it goes
into the counter chip. This is another area to look. The manual may
tell you what the counter presets should be for various bands when
the VFO jumper is removed. If these are correct, then the preset circuit
is working and the PTO signal is just not getting in. As always, check
the "mass term" connectors and the harness wires that attach to them.
Sometimes the connector is ok, but the wire isn't in tight.
73, Bob WB2VUF
Irena & Richard Jenkins wrote:
>
> Hi there everyone...
>
> I have a 580_Delta ... which I have had since 1985. Until a little
> while ago it has given me no problems. Now the rig works perfectly ...
> and I can use it for casual SSB contacts from this (holiday) location.
> However, the digital readout has failed ... in that it reads a fixed
> frequency ... which is different for each band. It seems like a crystal
> frequency ... but not one I can directly relate to.
>
> Earlier suggestions included checking the the VFO_OUT/IN bridge was in
> place. This is correct ... although I can see that the absence of a VFO
> signal to the display gives the symptoms I can observe. I next looked
> at the mixer (a double_gate FET ... on the display board. Although this
> seemed to be faulty, replacing it with a new one did not produce a
> result! I'm stumped. Not being in the repair game I find it difficult
> to get my head around the possibilities.
>
> Any suggestions would be sincerely appreciated, because this fine rig is
> an excellent performer. The fixed dial frequency is a bit off_putting
> however.
>
> Can you help??
>
> Richard
> --
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
> Irena & Richard Jenkins rjenkins@batemansbay.com
> Batemans Bay (NSW)
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>
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