Thanks for the replies to this, both on and off list. Repairs to the wiring turned out to be fairly straightforward and all now seems to be basically functional, but there still remains the problem of the lamp. I am told that the FRK lamp is not a direct replacement, the base is smaller, but that it might be possible to modify one to fit. Which leads to another question, does anyone know of a source of spare working FRK lamps, or even just one? Nigel, GM8PZR ---------------------- A friend of mine has bought a just out of calibration R & S XSRM Rubidium standard from one of the so called "recyclers" on Ebay. Although the price was good, and it came with the off air receiver, phase meter, and frequency divider, it looks to have been heavily decommissioned with deliberate damage to the internal wiring and the rubidium lamp removed. We've found the relevant manuals online and he's confident he can repair the wiring but he still needs to locate a lamp. If anyone has a working lamp available, or might know where one could be obtained, please contact me off list. He did comment that the lamp assembly looked as though it might accept the lamp from an Efratom FRK, can anyone confirm this? Alternatively, is there likely to be any risk of damage to the FRK lamp or to the XSRM lamp driver if he tries it but it's not compatible? Nigel, GM8PZR