WA4VZQ wrote:
Jeff, N6NMI, wrote in message news:ce12ab6a
...
Is there a 651S-1 mod that retains the last listening frequency when
the radio is turned off? Now I get ".0000" each time I turn the radio
on, regardless of what frequency I was tuned to when I turned it off.
A youtube video shows the radio coming up tuned to 20 meters when it
is turned on: how is this implemented?

I added a 6 VDC source to the terminal strip on the back, and that
retains the frequency when I unplug the radio, but when I turn it off
using the power switch it still comes up .0000 when I next turn it on.

From the website, http://www.collinsmuseum.com/651s1.html:

"FREQUENCY MEMORY KEEP-ALIVE POWER
Used to maintain storage of frequency information during power
interruptions. An external 6- to 8-volt battery supplies the necessary
power for the circuit. This option is implemented by wiring the special
keep-alive assembly into the chassis subassembly. Refer to the
configuration chart for status numbers of receivers that include this
option and for the part number of the chassis subassembly that includes
the special keep-alive power assembly."

That's the skinny. We used a rack of four of them at the U.S. Embassy
in Guinea-Bissau in 1987-89. Each had been modified by having its blue
fluorescent displays replaced with LEDs. The receivers each had had a
6-volt gel cell. All the gear was replaced by Harris equipment shortly
after I left in September, 1989 and was replaced by Harris equipment.