Re: Cossor 3339 Oscillograph(Scope).
My wife has gone to visit her father for a few days ..... the cats away etc .... Have taken over the kitchen to work on the 339's - see attached photos. I decided to start at the back of the scopes and work forward. The chassis of the 339B is not in too bad nick so I am going to try and keep that as original as possible. All the rubber wire insulation is perished and I have been quite surprised at how brittle the heavy duty single strand inner copper wire is where it enters the solder, several have broken on the least movement - it must have "work hardened" over the last 70 years. I am therefore replacing all the wiring. As I remove and replace a wire on the old chassis I am putting a new one on the resprayed chassis. Along with labels and annotating the circuit diagram I hope to be able to keep track!! All the components are being checked as I get to them. All the 1500v 0.5µF metal cased capacitors showed no leak at 540v (as high as I can get) so will hopefully be OK.
Interestingly some old repairs were wrong - electrolytic polarity reversed wrong values etc, also, one original joint had not been soldered at all and a couple of dry joints so far - hope that I can do better. I have an original 339 blue print which I think Sean gave to me, it does not quite match the diagram in the 339 manual. If anyone is interested I will copy the relevant bits.
Mark
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