Dear Time-nuts, I have been following the list for a number of years from the sideline. A lot of interesting discussions taking place. I'm sending this mail, because I'm looking for some information on the RACAL SA500 frequency standard. The RACAL SA500 is part of the RACAL MA259 system. It consists of a 5MHz reference oscillator and a backup battery unit. Recently I acquired the complete oscillator and a partial backup battery unit. During the Holidays I powered up the oscillator from my lab power supply. The unit seems to be working almost fine. A very nice (on the spectrum analyzer) 5 MHz signal comes out. When checking the readings on the meter, most readings are approximately okay. However, the temperature setting moves the meter below zero, so there is a small error somewhere. The SA500 looks a bit like the Sulzer 5MHz standards. For the MA259 system a manual can be found on the KO4BB website. However, this manual is for the old type of reference, with the "analog" frequency dividers. The unit I have is much more modern, with logic-ICs instead of transistors! Now I'm looking for schematics, or even better, a service-manual for this modernized MA259. The PCB-boards inside are labelled "RACAL". I hope someone has a PDF of the manual, or can provide a pointer to the correct manual. Most manuals/schematics available seem to be the same as the document from KO4BB. For identification, I include some pictures. Thank you for your time & help. Best regards, Jeroen Bastemeijer