EMS SYNTHI 100 restoration

Working on the Dawe 3000A Frequency Counter:

It was decided to restore the ‘test equipment’ sections of the Synthi 100 first, as these items would prove very useful during the fault-finding and calibration of the rest of the instrument.

As it arrived the counter would power up and display a static row of random digits which did not change. Pressing the mode buttons would sometimes cause it to start counting, other times it would do nothing. One of the Nixie segments was missing from the 3rd display, and the left-most display always got stuck between 6 and 7.

The first task was to remove all the cards and clean the oxidisation from the edge connectors. Next, to clean the push switch contacts, and free-up the 2 stuck slider switches. After that, it worked rather more reliably. However there were still some issues to be resolved.