[R-390] Intermittent Calibrator Signal

[Steve Hobensack]

The calibration signal comes from a multi-vibrator cicuit at the back right hand corner of the rf deck. The circuit involves a 5814 dual triode tube and a crystal module. The crystal module has an octal plug and can be removed easily for testing. The best test is to insert a know good module.

If the problem persists, the tube or involved circuits are responsible. If the module is bad, sometimes they are repairable. it contains a 17 mHz crystal and a 200 kHz crystal. Do not mess with the 17 mHz crystal. The 200 kHz crystal can be opened and cleaned. Look for a broken copper lead going down into the pin. Clean the crystal with soapy water and dry with lint free cloth. Handle the cleaned crystal by its edge or use clean tweezers. Clean the steel pressure plates also. Be sure to remember how the crystal and pressure plates came out of the holder. Fair Radio used to sell these modules but that was years ago.

Steve N8YE