AXT Systems

Dual 1176LN Release Pot
One part that was difficult to locate was the 5Meg Release potentiometer. It would appear that stock rationalisation has in many cases limited the availability of high value potentiometers. The highest value obtainable was 2Meg, so I set about trying to do the same job with a dual 2Meg pot configured in series.

The Release pot configuration is that of a variable resistor, with the fixed resistor setting the lower value and the pot resistance the upper value.
Adjusting this fixed resistor value slightly allows me to match the lower value in the CCW position. The maximum value is now 4Meg instead of 5Meg, which reduces the maximum release time by about 25%.

A spreadsheet was created to plot the end-to-end resistance curves of both linear and logarithmic types of pots for both the 5Meg and 2Meg dual configurations. Notice how the 274K resistor has been changed to 300K to achieve the CW resistance of 260K.
Release pot replacement
Original circuit (left) and replacement circuit (right)
Comparison of pot curves
Comparison of pot curves