National CRO Oscilliscope

[jr_tech]

Looks like a simple ham modulation monitor, likely for displaying trapezoid patterns when connected to an AM transmitter. I suspect that it is very similar to this smaller CRM model:

http://www.oscilloscopemuseum.com/os...-crm-sxxx.html

http://www.oscilloscopemuseum.com/up..._schematic.jpg

jr

[Zsuttle]

Well, some of the values on the resistors differ, but they're known values. Any idea for a range for the filter caps?

[jr_tech]

The 2 inch model (CRU) isn't much different in design from the 1 inch CRM:

https://stevenjohnson.com/oscillosco...tional-cru.pdf

But i'm guessing that the 3 inch model might use somewhat higher voltage. The max for the 3 inch CRT is specified as 1500 Volts, so C2 might have to be rated at a higher voltage.

jr

[ChuckA]

Originally Posted by Zsuttle

Well, some of the values on the resistors differ, but they're known values. Any idea for a range for the filter caps?

There is only one filter cap, it's 1uF @ 1000V

Chuck

[Zsuttle]

Then, anyone have any advice on where to get this type of a capacitor? I've yet to see an electrolytic with such little capacitance but such a high voltage. I've seen quite a few of the film style though, and at reasonable prices. Would using one of there in series with a diode (say a 4007) work as a substitute? I'm not very well versed with caps, but something tells me that this wouldn't work (Though doesn't stop me from asking)

[ChuckA]

They're not electrolytic.

Is it bad ? I can't remember what is actually in it, but usually they are oil filled cans and rarely are bad.

If it is bad you can use a couple of 2uf @600v units in series.

Chuck

[Zsuttle]

Originally Posted by ChuckA

They're not electrolytic.

Is it bad ? I can't remember what is actually in it, but usually they are oil filled cans and rarely are bad.

If it is bad you can use a couple of 2uf @600v units in series.

Chuck

I wish it was oil filled, It tested leaky and I decided to restuff the enormous container. It's a pretty standard metal housing, paper innards, tar filled, pain in the rear, cap.