Re: Damaged 606

Roger Evans

Before you give up all hope, check for very large values of ripple on the -30V and +120V supplies. The bulk smoothing capacitors can go low capacitance / high ESR with age and you get almost 100% modulation of the raw DC into the low voltage regulator. As a quick fix you can just tack on an external capacitor in parallel, even on long leads, to see if the distorted trace returns to something more nearly normal.

The -30V biasses the X and Y amplifiers and if it goes way out of spec twice every mains cycle you will see the spot trace out a possibly complex shape as the amplifier operating point changes. I saw something similar on a 475 with three power rails showing large ripple and the timebase not working due to an open circuit switching transistor.


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