190VDC Reference Revisited.

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MED6753
Posts: 487
Joined: Sun Oct 23, 2022 6:02 pm
Location: Middletown, NY USA

190VDC Reference Revisited.

Post by MED6753 »

Finally got some lab time after nearly 2 months of doctor's appointments and other assorted distractions. Yes, Blondie is doing well. Revisiting a 190VDC reference that I built up several years ago. It was never very stable and in fact quit working all together. Discovered that the Inverter card would spike to over 270VDC at initial turn on which blew out the LR-8 regulator. This was solved by adding a 100K/2 watt resistor across the Inverter output. Replaced the LR-8 regulator and now have a much more stable output.

Schematic
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Internal view.
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External view.
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Results in low res mode.
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Results in high res mode.
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Cross check on a 8800A
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The reference was allowed to stabilize for about 45 minutes. I would consider it accurate enough to check/calibrate 3.5 and 4.5 digit DMM's but not something like the 3456A. So now I have a complete set of 190mV, 1.9V, 19V, and 190V references.
An old gray beard with an attitude. I don't bite.....sometimes :twisted:

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