Inspiration for a kit

The new Morse Dial Timer mentioned yesterday:

https://wb9kzy.blogspot.com/2025/05/a-new-kit-for-2025.html

was inspired by a couple of products I've noticed over the years.  First was the PRC-74 solid state transceiver used in Vietnam:

https://wb9kzy.blogspot.com/2022/09/just-dream-prc-74-transceiver.html

and the RF-301 transceiver:

https://wb9kzy.blogspot.com/2023/01/radio-with-thousands-of-channels.html

The main idea was setting the frequency with rotary switches, they serve both as a "dial" and as a "display", neat, just pivot the idea to a timer !

And of course the second, more direct inspiration was the Heathkit PT-15 photo timer:

source: https://www.ebay.com/itm/334835327435
 

It's an RC hardware timer with a OA2 tube (!) to regulate the line voltage.  But the delay is set in 2 decades, there is also an x10 slide switch, start momentary switch and a stop slide switch.

The Heathkit catalog listing for the PT-15 in 1977:

The semi-obligatory inflated price:

Heathkit later came out with the PT-1500 timer with a keypad, LED display and microprocessor control but I think they lost the elegance and simplicity of the PT-15 design.

A previous Heathkit timer, the ET-1:

source: https://www.ebay.com/itm/286265564708

used a bakelite box with aluminum top plate and a single pot to set the time.  I used the aluminum top and bakelite box in the Morse Dial Timer.  But the single pot was no good for setting the time to the minute.  It was too hard to get it right on the money even with a large pointer knob.  I also tried two pots with detents but that was also kinda iffy.  I finally settled on two decade switches with a string of 1 percent resistors to reliably set the time interval.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm