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Old 1st Mar 2018, 10:53 pm   #33
MotorBikeLes
Nonode
 
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,346
Default Re: Oscilloscope not used in years

OK Dave, my observations:-- With most of these older valved TQ scopes (all of which I would repair and fully calibrate before sale) a few had occasional low EHT (HV rectifiers going resistive) which if they failed my relaxation oscillator test, would be replaced by B&W TV EHT diodes. A very few needed one of the 100Ufd caps in the HT doubler circuit replacing. Quite a few resistors going high value. Only the very old S31 and D31 had brown German capacitors (Wima) already dead or dying -- replace on sight. I did have a very few transformers with O/C or shorted turns.
Obviously calibration showed a few valves that needed replacing, though I generally tested all of them (I had an Avo Mk.IV) and either replaced or moved to a less important location. I was lucky having a big stock of ECF80 and ECC88 which fitted most sockets. Anything else was the odd thing you just have to trace out using logic. I had very few TEK valved scopes, and quickly learned that apart from TQ and TEK, very few valved scopes were worth touching. I had a couple of Marconis (2200/2200A) but so many valves you were likely to hit faults, plus dozens of not very reliable carbon resistors causing uncontrollable free running or other problems (but they must have been fantastic scopes when new). Big solatron, like the Marconis, Advance, poor, Hartley, terrible. I found I could make some money from TQ scopes, but obviously the later solid state ones were better.
Les.

Last edited by MotorBikeLes; 1st Mar 2018 at 10:55 pm. Reason: added Wima
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