Core what a lot of queries about test equipment accuracy
I have for some time been on the lookout for an off air standard. As far as I can see these things receive the same signal the BBC use for the pips before the news on radio 4. A broken radio controlled clock would also be a candidate for making a home brew off air standard too.
A 10Mhz clock is divided down and phase locked to the pips themselves.
All you need to do is put the clock from the off air standard on one trace of a scope and the clock in the DFM on the other trace.
My Racal shown in the earlier post has a crystal oven in it so it is quite a posh one from the 1970s.
So back to the Marconi.
I took the cover off the oscillator and checked the resistors and as I predicted some of them are actually high and out of spec the wort of these being on the lower ranges.
The worst were the two 820K ones on the lowest range. These were reading over 1 meg.
I have not yet fitted the new ones due to a dinner call although I did get time to select them from stock parts.
With all the Qs and As about test equipment accuracy my big Fluke came into play in order to double check my every day DMM.
The access to replace the resistors is easy enough so it is not a lot of bother to sort out.