Author Topic: help with oscilloscope model 34  (Read 9229 times)

whomeno

Re: help with oscilloscope model 34
« Reply #120 on: October 16, 2018, 07:13:55 PM »
if i set meter to 2v I get 1 error
set meter to 20
probe + 1.64
probe-  1.62
probe earth= 1.61
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Rob Strand

Re: help with oscilloscope model 34
« Reply #121 on: October 16, 2018, 07:37:52 PM »
Quote
if i set meter to 2v I get 1 error
set meter to 20
probe + 1.64
probe-  1.62
probe earth= 1.61
I think you did the test wrong.
For the leakage test only you need to set the meter to 2mA DC.
When you finish the test set the meter back to volts.
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #122 on: October 16, 2018, 07:46:53 PM »
meter dose not have a 2 ma - 600v 200v 20v 2v 200m
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whomeno

Re: help with oscilloscope model 34
« Reply #123 on: October 16, 2018, 07:53:26 PM »
i'm sorry i found it.
getting 0 on all
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whomeno

Re: help with oscilloscope model 34
« Reply #124 on: October 16, 2018, 07:57:10 PM »
I am using c33a as 400volt source
dimm - to ground
each lead of probe to dimm +
1 at a time
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Rob Strand

Re: help with oscilloscope model 34
« Reply #125 on: October 16, 2018, 08:00:18 PM »
Quote
i'm sorry i found it.
getting 0 on all
Not good.   
I think the fuse in your meter is blown.

You can check the fuse as follows using a 9V battery:

- Set meter to 2mA DC

- Connect up a circuit like this (a big circle)

        +9V  ->  10 k ohm resistor ->  Meter + terminals
and    0V    ->   Meter -  terminals   

- Take the measurement.
   If it is 0.9mA then the fuse is OK. 
   If it is 0 then the fuse is blown.

- Set the meter to 2V DC.
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #126 on: October 16, 2018, 08:35:04 PM »
fuse is shot.
will need to find another one.
will let you know when back up and running
Gear as of now
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Marshall DSL40cr
Peavey valveking2

Rob Strand

Re: help with oscilloscope model 34
« Reply #127 on: October 16, 2018, 08:39:13 PM »
Quote
fuse is shot.
will need to find another one.
will let you know when back up and running
No worries.
What can happen is if you are measuring a voltage and spin the meter switch over any of those mA or A ranges it will create a near short across the meter leads and normally blow the fuse.   You should watch out for this because it can create a hazard (and blow-up the circuit).
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #128 on: October 16, 2018, 08:41:48 PM »
ok will do need to order some in.
nobody around here has them
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Marshall DSL40cr
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Rob Strand

Re: help with oscilloscope model 34
« Reply #129 on: October 17, 2018, 01:29:11 AM »
Quote
if i set meter to 2v I get 1 error
set meter to 20
probe + 1.64
probe-  1.62
probe earth= 1.61
Your meter has some funky behaviour.

The previous battery +10M test in Post Reply #88 shows the multimeter input impedance is 1MEG on the 2V range.  For 1M input impedance I would expect the result of this "incorrect" test to produce 6.7V,  which is expected to overload the 2V range (ie. the  "1" on the DMM display).

However for the 20V range we don't get 6.7V we get 1.6V.  That implies the input impedance of your meter on the 20V ranges is only 244k ohm.   So it has dropped by a factor of 4.   An input impedance of 244k ohm is quite low for a DMM.  Notice also if you were on 20V range and saw a 1.6V reading you would think you could step down to the 2V range but when you did it you would get an overload.
« Last Edit: October 17, 2018, 05:32:37 PM by Rob Strand »
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #130 on: October 17, 2018, 09:34:01 AM »
leak down test
probe + lead = .006
probe - Lead =.006
probe earth lead =.006
meter set on 2ma
Gear as of now
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whomeno

Re: help with oscilloscope model 34
« Reply #131 on: October 17, 2018, 09:45:52 AM »
redid the 10m ohm test
on 20v it gives a 0.86
on 2 v it gives a 0.867
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Rob Strand

Re: help with oscilloscope model 34
« Reply #132 on: October 17, 2018, 05:33:32 PM »
Quote
leak down test
probe + lead = .006
probe - Lead =.006
probe earth lead =.006
meter set on 2ma
OK, all those look good.
The mind often distorts without gain.

Rob Strand

Re: help with oscilloscope model 34
« Reply #133 on: October 17, 2018, 05:37:38 PM »
Quote
redid the 10m ohm test
on 20v it gives a 0.86
on 2 v it gives a 0.867
Hmmm.  From those measurements the impedance works out to be 1M ohm on both 2V and 20V.  That's more of a normal result.

Not sure what happened in the previous test.    It worries me when I see weird results.
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #134 on: October 17, 2018, 06:22:43 PM »
kewl, so what is the next steps
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whomeno

Re: help with oscilloscope model 34
« Reply #135 on: October 17, 2018, 07:09:47 PM »
I will replace resisters and capacitors if need be. Would like to know if the 5Up1 is ok.
On the resistors that is not marked with a wattage ,what size would I use?
Gear as of now
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Rob Strand

Re: help with oscilloscope model 34
« Reply #136 on: October 17, 2018, 07:45:27 PM »
Quote
kewl, so what is the next steps
The next steps you have to be freaking careful as you need to measure dangerous voltages!!!
You have to make sure all the connections are correct, the meter is set correctly
and you are probing the right points, even which side of the resistors,  *before you start*. 
Plan it all out up front.   

Don't measure anything yet.  I'll mark-up the schematic.

The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #137 on: October 17, 2018, 07:50:00 PM »
ok I replaced R63 220k measures 260 now instead of  360
Gear as of now
Gibson 2017 Les Paul Tribute T
Marshall DSL40cr
Peavey valveking2

Rob Strand

Re: help with oscilloscope model 34
« Reply #138 on: October 17, 2018, 08:30:32 PM »
Quote
I will replace resisters and capacitors if need be. Would like to know if the 5Up1 is ok.
On the resistors that is not marked with a wattage ,what size would I use?
These days the best resistors for that part of the of circuit probably Flame Proof Metal Oxides.
I'll have to check you pics for the wattage.   
The caps are special items. 

Quote
ok I replaced R63 220k measures 260 now instead of  360
I'm not fond of using standard resistors in HV circuits.   The standard resistors only handle 250V.
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #139 on: October 17, 2018, 08:38:51 PM »
i had some old stock here. it is the same type of resistor. that is why it read 260 instead of 220.
Gear as of now
Gibson 2017 Les Paul Tribute T
Marshall DSL40cr
Peavey valveking2