Description

Do you have a Sinclair DM235 meter with a blown resistor network? If so, this is just the part you need! I have reproduced this previously impossible-to-find part so you can get your trusty old meter working like new again. It may work in other Sinclair models (I don’t have any others to compare with so I don’t know. If you find another meter which this divider will work in, please let me know.) Even if you don’t own a meter that this will fit in, it would work nicely as part of a DIY project. Note that the ‘missing’ resistor in the picture will be present on the part you receive – it is not needed in the DM235 so I omitted it in the prototype.

Specifications:
-0.1% tolerance
-Replaces Sinclair P/N 23301-807 (Parts are marked the same as the originals – 744388 WEL)
-All the resistors except the 9M resistor are implemented with 1/8W Vishey TNPW series precision surface mount resistors
-The 9M resistor is implemented with one 1/4W Vishey/Dale CMF55 series precision metal film resistor and one 1/4W Ohmite MOX200 series precision thick film resistor.

Download the schematic and PCB layout for this product here. Note that these files are available for PERSONAL, NON-COMMERCIAL USE ONLY. In short, you are welcome to use them to build this product yourself, but you must contact me to work out a commission if you wish to sell anything derived from them. This product was designed in ExpressPCB so you will need to download a copy of that software fromexpresspcb.com before you can view the files.