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Re: Positonal Hum



Al,

In my experience this supply has not been a major contributor to Positional Hum.

Most Turbos had this supply replaced by a separate regulated 70v supply because
older machines (which most Turbos were made from) only had a 50v supply
available to run the line timebase, and to achieve full range of XY zoom
you need the full 70v.

I have found that most positional hum is caused by radiated magnetic fields,
rather than electrical hum on power supply rails. Therefore I would suggest
you check:
        1. Digiscan PSU (Hewlett Packard fans radiate something rotten).
        2. External influences, such as power wiring close by.
        3. Internal Scan & Signal, & Traction (both transformers have
           Mu Metal screens that should be in place.
        4. Amplitude hum on the XY zoom control lines (Does it change between
           local and remote?) Amigo (remember that) was a prime culprit.

Hope this helps

Paul Chapman