[MelJon66]

It is with great sadness that I have to report that battleship HMS Cossor CDU150 has sunk to the bottom and is probably beyond economical rescue. Unless you know otherwise!!!

Yesterday I checked all the LV supplies and they were spot on. I then checked the EHT and adjusted to the required -1140V. It had been -1170V so it had been a bit out. The anode voltage was then checked at 11.16kV which was also spot on. The trace was sharper and the focus worked well so I was well pleased. I had some trouble with the beam current but that is irrelevant now.

Later in the day the scope was taking a very long time to produce a trace and then it was a bit jumpy. I found that the 50V and 12.6V LV supplies were not producing any output. It was difficult to check why as by the time I got in there it had warmed up and the outputs were back. I suspected a bad joint or a dodgy bridge rectifier.

Today it won't switch on at all and I have found that the transformer secondary to the 50V supply (secondary taps m and n on circuit A) is open circuit at 5M ohm. The 50V supply feeds the regulation circuit of the 12.6V supply so this is reading very low too. Strangely the -50V supply takes input from the +50V but this still works.

So, the failure is just down to old age I suppose and is probably terminal. I will hang on to it as these machines are either given way or very cheap and one might pop up when the lockdown is over. Patience pays with these things.

My next project is a HP 1743A. I know someone has already been messing around with it big time as it came with a bag of bits that were left over from the last attempt so I am expecting trouble! I will not rush into this project and it will proceed slowly as I am also converting a campervan. I will post something when I get started.

Thanks for your contributions.

Cheers
Mel