2022-11-01 (or thereabouts)

It happens from time to time that a man becomes obsessed with a project and can't seem to stop wasting time on it. This is one of those projects that has repeatedly seemed to be easy and something continues to elude me... There's been plenty of magic smoke though..

It has become very apparent that Stearns SINPACs have become un-obtainium over the last 2 years... And I keep getting asked for them. They've gotta be simple, right? I've been blessed with quite a few blown ones and decided to investigate.

This is the first blown SINPAC, a CV40-165; but perhaps I should supply a DATASHEET

...for the first time ever, I've managed to extract one of these ceramic boards from epoxy without breaking it!
U?: A393F Dual Comparator
Q?: A42 NPN Transistor
Diode between the two: marked M1 - possible MMSZ5256B 30V zener diode from DIODES INC? (PDF, 5 Pages, 370kb)
Other diode: marked T4 - possible 1N4148 Switching diode from DIODES INC? (PDF, 5 Pages, 285kb)

Back of the board - CV165-37 1402L

Front of the board without surface mount parts. Notice the laser marks in the black resistor layers.

Main Circuit Board Bottom

Main Circuit Board Top

Electrical Diagram of the CV40-165 Circuit Boards. Also included in the diagram is the electric motor diagram. (Clicking on this will give you a nicer PDF version)

...and now, if I could only figure out why I keep blowing the LM393...hmm. Guess I'll just dive into the next one.


If you or someone you know finds this info useful and decides to start building something similar, please let us know. We'd like a royalty check and the option to buy some of your devices. ;)

Note: All electrical diagrams are believed to be correct as far as we're aware; however, there may be mistakes and omissions. You assume any and all risks by using these diagrams for anything other than a pretty picture to look at.


Part 2 of the un-obtainium saga: the CV25-165

Part 3 of the un-obtainium saga: the CV50-165

Part 4 of the un-obtainium saga: Alternatives - SAMUSCO ECS224L

Psalm 69:14