On Wednesday 27 November 2024 03:46:21 pm wn4isx via groups.io wrote:
I've been working on a Simpson 460-3 DVM with analog sub-meter.
I've done a bit of work on my Simpson DVMs, not fun!
There are 2 primary scales, .200V and 2.0V, all the higher voltages are attenuated to one of those.
The zero and +/-2.0V was a breeze, the .200V has been a nightmare. Two controls interact. After switching the Vin bananas a few dozen times I decided enough and rigged a special 'calibration cable' with a 4PDT switch with gold/palladium contacts as a DPDT to reduce any contact resistance.
To change from Vcal+ or - to the opposite means flipping the switch.
I've got it so the V+ is 10.00V, and the V- 10.01, I'd prefer V- to be 10.00 but I'll accept what I've got.
Okay...
I obtained this meter because of the analog sub meter. Aligning RF stages is a challenge with a DVM, the analog meter is an ~3 inch wide and ~0.5 inch wide edge meter and very nice for peaking and nulling RF stages.
I've managed to accumulate a few analog meters here for such stuff. None of them have especially high input impediance like a DVM would have, but that's okay.
My next project is assembling a Heathkit IM-28 VTVM. While labeled as a VTVM it is actually a FET and opamp meter.
Advantages are that you don't have to wait for it to warm up, I guess. Disadvantage is that it's not anywhere near as robust as a tube would be in the event of overloading the input.
As I've noted before, I no longer use alkaline cells because of repeated leakage problems and use primary lithium. Lithium cells have a ~10 year life expectancy and don't leak.
Right. What does that meter take?
Can you drown in test equipment.
Check out "Mr. Carlson's Lab" on youtube, I don't know how that guy manages to get all that stuff stacked up that high. If it ever falls on him he's gonna be in some serious trouble! :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
