I looked through every page I have, but no luck. Sorry.
I never tinkered with these models.
Hope this helps though !!!!
Good Luck with your search !!!!!
I did Google "Sun RC Tachometer" and found lots of articles and info.
Here's a couple of samples,
http://67-72chevytrucks.com/vboard/s...d.php?t=392461
http://www.bobsspeedometer.com/1/120...sp?artID=43376
https://www.jalopyjournal.com/forum/...meter.1030481/
https://picclick.com/Used-Vintage-Su...601544109.html