help with oscilloscope model 34

Started by whomeno, October 11, 2018, 11:24:12 AM

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whomeno

if i set meter to 2v I get 1 error
set meter to 20
probe + 1.64
probe-  1.62
probe earth= 1.61
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

Quoteif 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.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

meter dose not have a 2 ma - 600v 200v 20v 2v 200m
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

i'm sorry i found it.
getting 0 on all
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

I am using c33a as 400volt source
dimm - to ground
each lead of probe to dimm +
1 at a time
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

Quotei'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.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

fuse is shot.
will need to find another one.
will let you know when back up and running
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

Quotefuse 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).
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

ok will do need to order some in.
nobody around here has them
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

#129
Quoteif 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.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

leak down test
probe + lead = .006
probe - Lead =.006
probe earth lead =.006
meter set on 2ma
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

redid the 10m ohm test
on 20v it gives a 0.86
on 2 v it gives a 0.867
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

Quoteleak down test
probe + lead = .006
probe - Lead =.006
probe earth lead =.006
meter set on 2ma
OK, all those look good.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

Rob Strand

Quoteredid 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.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

whomeno

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
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

Quotekewl, 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.

Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

ok I replaced R63 220k measures 260 now instead of  360
Gear as of now
Gibson 2017 Les Paul Tribute T
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals

Rob Strand

QuoteI 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. 

Quoteok 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.
Send:     . .- .-. - .... / - --- / --. --- .-. -
According to the water analogy of electricity, transistor leakage is caused by holes.

whomeno

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
Epiphone Les paul Special (upgraded)
Marshall DSL 20 Head
Peavy Valve king 20 W
2 X 12 Cabinet with celestion vintage 30 & celestion G12T-75
And a lot of pedals