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Old 3rd Jul 2013, 11:38 pm   #53
Leon Crampin
Octode
 
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
Default Re: Tektronix 465B Scope - Some problems.

I've been following this thread with interest as a confirmed Tek admirer and user.

Why not disconnect the deflection plates and join x to x' and y to y' (on the tube) with short pieces of wire? This should eliminate the possibility of noise or interference giving a thickened trace. If the EHT system is giving all of the correct electrode voltages, a CRT fault remains an unfortunate possibility.

Tek portables can suffer from loose screws securing pc assemblies which also double as earthing points for the tracks. Likewise, any loose fixings on (by now) slightly corroded or tarnished screens can give this effect. Also, the Fairchild plastic "TO-18" devices so beloved by Tek are non-hermetic and end up noisy or faulty. Replace with metal can devices. Finally, check the decoupling to the EHT oscillator (47uF from memory).

The 465B was my all time favourite portable work horse - used in the field in unspeakable conditions, in the rain and powered from a diesel generator. Impeccable performance at the time.

Best of luck with your problem.

Leon.

David, I'm afraid for me, Tek were the King of 'scopes but my H-P 41 holds a similar position as a problem solving machine. Mine has worked impeccably since about 1980. Both organisations have a proud history of achievement.

Last edited by Leon Crampin; 3rd Jul 2013 at 11:45 pm.
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