Murata trimmer caps

 Here are a few observations on Murata trimmer caps:  

1) The yellow cap aka TZ03P450F169B00  is specified as a 6.8 pF to 45 pF trimmer capacitor.   I tried measuring one using a B&K 810C capacitance meter and got a range of 6.8 pF to 55.4 pF.

2) The terminal on the rounded end is directly connected to the brass rotor (verified with an ohmmeter) so it is usually connected to ground in a circuit.   When the round end is grounded a metal adjustment tool will not cause a significant shift in capacitance when it touches the rotor.

3) There are two square "dots" on the brass rotor that give the user an indication of the capacitance setting.  When the two dots are towards the rounded end the cap is at maximum capacitance.  When the dots are at the flat end the cap is at minimum capacitance.

4) Unfortunately Murata doesn't make these caps anymore although there may be subs from other vendors.  Luckily I did buy a bag of 1000 pc. a few years ago so I should be set for life :)

Here is the drawing of the cap from the Murata spec, notice from the square dots position that the cap is at maximum capacitance:

Here is the cap installed on a VE3DNL marker generator board from FAR Circuits:

Here is that VE3DNL board along with a nice adjustment tool from Vectron Labs that a GTE co-worker gave me:

I've tried making my own adjustment tools from bamboo skewers or old nut starters with a metal blade installed, nothing works quite as well as something like this Vectron tool (Vectron made oscillators used in telephone systems).

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm