Re: Type 503 Oscilloscope Issues

Dave Casey


The diagram I promised is attached. As for your other issues, you mean to
say you have about -85V on the -100V bus? Do you also have about +85V on
the +100V bus? If so, then I would suspect V620 as having been weakened by
the stress, though there are certainly other possibilities.

Dave Casey

On Apr 24, 2017 10:52 PM, "enchanter464@... [TekScopes]" <
TekScopes@...> wrote:

Hello all,

The filament transformer came in today, and to Hank's concern, looking at
the data sheet on Digikey, the 6.3 VAC transformer does support an
isolation voltage of 2500 Vrms, which should account sufficiently for the
-3000 V load (as noted by Dave). It is also the same breakdown voltage (and
other specs) as the older model transformer that Mike had used, so it
should work for the repair.

However, this brings me to my current issue. When adjusting R641 (the -100
V adj), there was no change in the voltage reading at the -100 V bus, still
measuring at ~85 VDC, even with the dial changed a significant amount.

Is there something I am overlooking in adjusting the voltage, or could
there be another component (Aside from the transformer) affecting the
baseline voltage, as Albert had noted?

- Evan

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