Does anyone have an opinion on it's accuracy, releablilty, history of design problems, service modifications or restoration issues?
Any and all comments would be appreciated.
Gary
I had a Mk3 for a number of years, but sold it when I got a CT160.
The Mk3 is a good instrument, and is very reliable, though it does have a valve rectifier inside for the screen supply (EB91). All other electrodes are supplied with AC, and measurements taken by a bridge method, which gives high accuracy and repeatability.
There are a good selection of sockets on the machine, but it does not have sockets for Nuvistors or Compactrons as standard (the AVO VCM163 does, if you can find one!).
These instruments are valve characteristic meters rather than valve testers, and are geared up for taking sets of valve characteristic curves in a lab enviroment. The can be used as testers, but the "backing off" process to take gm measurements is time consuming if you have a lot ofvalves to test (the AVO CT160 is easoer to use in tester mode).
As for faults, the main problem is dirty control pots, which can be easily remedied. There are a couple of firms in the UK offering refurbishment service for the meter movement as well.
I still have a copy of the manual, if you need it.
The other thing you need is "The AVO Valve Data Manual", which was supplied with each instrument, I think the last edition was the 17th (the higher the edition, the more valves covered). There are some copies available, but they run to a lot of pages = expensive.
Jim.