067-0500-00/Repairs

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Revision as of 17:46, 26 September 2023 by Jadney (talk | contribs) (Created page with "In order to allow my 3M1 to work with 40 V pulses, I added a second resistor in parallel to R104, increasing the quiescent bias point of the 6DJ8. The resistor I added was a 620 kΩ, and the resulting parallel combination measures ~185 kΩ. This now works perfectly in my 564B. It should work equally well in any 560 series scope. You can see the extra resistor piggy-backed on R104 in the last two photos of the 3M1. It's worth noting that the input circuit in the 3M1 a...")
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In order to allow my 3M1 to work with 40 V pulses, I added a second resistor in parallel to R104, increasing the quiescent bias point of the 6DJ8. The resistor I added was a 620 kΩ, and the resulting parallel combination measures ~185 kΩ. This now works perfectly in my 564B. It should work equally well in any 560 series scope.

You can see the extra resistor piggy-backed on R104 in the last two photos of the 3M1.

It's worth noting that the input circuit in the 3M1 and the 067-0500-00 is different from the latest (067-0500-00) version. The latest version has a 56 V Zener diode in the center of that resistor chain. That version may require a different approach, but the approach above should be a good start. It's likely that replacing the middle resistor in the input divider of a 3M1 or 067-500 with a 56 V, 1 W Zener diode would be a good choice, but I chose the minimally invasive option.

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