help with oscilloscope model 34

[whomeno]

where would be the best place to get the Flame Proof Metal Oxides?

[whomeno]

I found them on digikey

[Rob Strand]

I found them on digikey

Bigger suppliers are more likely to keep them.

You have to get the correct power and voltage.
I don't know what's in the unit as it's not marked on the schematic.

Most old style carbon composites, the ones that are in the unit now, were 700V to 1000V.   At least that's what was quoted in the day.    Modern carbon composites are somewhat less for the same size package.

The voltage you want is working voltage (not overload or dielectric withstand).  Without any additional info a 1000V rating is safest.

"Limiting Element Voltage" comes up on the datasheet a lot.

[whomeno]

1000v what would that be in watts 1w 2 w?

[Rob Strand]

1000v what would that be in watts 1w 2 w?

They are completely different things.

No offense,  but I don't think you aren't up to doing this project.
You are going to get hurt. 
Stop!

[whomeno]

I just don't under stand .
you said use 1000 volt resistor
Resister are rated in watts not volts
on the schmatic it has which resisters need to be 1 watt -2watt and so on
if they are not marked as 1-2-3 watt what would the be?
smaller then 1 watt?
I ask question before doing any thing if I don't under stand.
I would love to finish this project. You have taught me a lot over the past days.

[bluebunny]

I just don't under stand .
you said use 1000 volt resistor
Resister are rated in watts not volts

If you look at the datasheet for a resistor, you will see that it has a maximum voltage rating too.

[whomeno]

I found a place that sells the same resistors used in the build.

[whomeno]

thanks bluebunny

[whomeno]

I hope I didn't make Rob mad at me. sure hope he helps finish this.

[whomeno]

measure votage across 60 62 63
intensity max
R60=7.68
R62 = .010
R63 = -2.161

intensity min
R60 = 5.914
R62 = .013
R63 = -1.57
done with new meter

[whomeno]

new meter is auto range and 10m input impedance

meter input impedance
battery = 9.60
with 10m resistor =5.01

Probe check
battery 9.60
with probe =.009

151v w probe= .154
234v w probe =.241
352.6 v w probe = .360
427.4 w probe = .436

resistance of probe
DMM- to earth =.4
dimm- to dimm + =OL
probe tip to earth =OL
probe tip to dimm=OL
probe tip to dimm+ =OL

leak down test meter set on auto dc volts
probe +  = 59
probe-  =  59
probe earth = 59

[Rob Strand]

I hope I didn't make Rob mad at me. sure hope he helps finish this.

I'm not mad.  I'm just concerned.   I've done this stuff a long time and I can see you have limited experience.  That's fair enough everyone is in the same position at some point.  This job is risky you can get electrocuted.   If your mind is thinking about how to set the meter you aren't thinking five steps ahead to avoid the dangers.

Imagine going on an climb to Mt Everest with limited experience.   It doesn't matter how experienced your guide is, you are at extreme risk.   Your guide can tell you stuff but  if you make a mistake tying one of the knots you will be in trouble.   The guide's not only thinking about the knots (which he can do easily) he's thinking about checking the knots and thinking many steps ahead, making choices so he doesn't get into trouble.   If you have limited experience you might not even be aware of the danger at all.   This is how you get in trouble.

Here's an example where you are close to danger. It's in the area of the power supply where
you are making measurements.   It's very easy to slip or make a mistake.

Click to enlarge:


I might add the unit is not Earthed. It uses a two-wire mains cable.

Also the mains inlet is just knotted and can push-in and get amongst the 1kV stuff.
That old mains cable is not rated for 1kV.

[whomeno]

I do understand your concerns. I know this can kill me that is why I have been taking my time and learning from you. Like i told you in messenger I have worked with 3 phase 440 and 410. But you have helped me through this so far and i hope we can continue or journey.

[Rob Strand]

leak down test meter set on auto dc volts
probe +  = 59
probe-  =  59
probe earth = 59

With the new meter the leakage test has to be done differently.

To measure current on your old meter you have to:
- Set the current range
- Use meter terminals  "COM" and "V".  ie. same meter terminals as the voltage measurements.

To measure current on the new meter you have
- Set the meter to current range
-  Use the terminals COM and mA/uA.

For the new meter there is essentially a short between COM and the 10A terminal and also a short between COM and the mA/uA terminal.

A good practice is to move the meter lead from mA/uA to V as soon as you are finished doing a current measurement.   If you leave the meter lead in the mA/uA socket and then later go to measure a voltage the meter will short out the circuit you are measuring and create a big bang.    Accidentally leaving the meter leads plugged into 10A then doing a mains measurement is a very hazardous situation because you are shorting out the mains supply with the meter.

[whomeno]

Set the meter to current range----That would be the ma  on the dial?

[Rob Strand]

new meter is auto range and 10m input impedance

meter input impedance
battery = 9.60
with 10m resistor =5.01

OK and that test confirms the meter is 10M

Probe check
battery 9.60
with probe =.009

151v w probe= .154
234v w probe =.241
352.6 v w probe = .360
427.4 w probe = .436

Ok those voltages look good.

FYI:  The R8 in the 1.5kV Probe was actually chosen for your old meter with 1M input impedances.
With the new 10M input impedance meter a value of R8=1M  should make the 1.5kV Probe should measure +5% higher.  However, because the parts have tolerances it is actually only 3% high; on the old meter it was 2% low.  Anyway, the accuracy is fine and there's no need to change R8.

resistance of probe
DMM- to earth =.4
dimm- to dimm + =OL
probe tip to earth =OL
probe tip to dimm=OL
probe tip to dimm+ =OL

The new meter only goes upto 20M ohm and we are expecting 60M ohm.   The old meter can go to 200M ohm, so it can do something the new meter can't.

[Rob Strand]

Set the meter to current range----That would be the ma  on the dial?

Yes.   Just set it to the 2mA range.

FYI: I think your new meter can do 200uA which will give a better measurement. 
You can try both.

[whomeno]

on ma ===0
on  UA all three are 6.8

[whomeno]

Have to go make supper. My wife has Brain cancer so I do all the work around the house. Be back in An hour.