Author Topic: help with oscilloscope model 34  (Read 9456 times)

whomeno

Re: help with oscilloscope model 34
« Reply #40 on: October 12, 2018, 04:55:29 AM »
I am so sorry I was using ac side not dc v7 pin 7 is 429v dc

v6 pin 1 300v   dose change
pin6  144v


v2 1   324v pin2  234v
dose not change much
« Last Edit: October 12, 2018, 05:00:10 AM by whomeno »
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whomeno

Re: help with oscilloscope model 34
« Reply #41 on: October 12, 2018, 05:03:44 AM »
still no line or dot to be found
with the probe it is 1.8v from 429
« Last Edit: October 12, 2018, 05:07:25 AM by whomeno »
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whomeno

Re: help with oscilloscope model 34
« Reply #42 on: October 12, 2018, 05:27:59 AM »
in the schmatic  v4 is a 6j6  my v4 is a 12au7
in the schmatic v7 is a 12au7  my v7 is a 6x4
will this matter?
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Rob Strand

Re: help with oscilloscope model 34
« Reply #43 on: October 12, 2018, 05:33:33 AM »
OK cool that's starting to make more sense.

Quote
still no line or dot to be found
You won't see a dot until both V2 and V6 balance,
 in that
Voltages V2 pin 1 = Voltage V2 pin 6, and
Voltage V6 pin 1 = Voltage V6 pin pin 6.

I suspect V6 is a good place to start.      The aim is to get Voltage V6 pin 1 = Voltage V6 pin pin 6 when the Horizontal position is set to about half way.  When you check the voltages make sure the width control (R44) is fully counter clockwise (ie the wiper at position 1 on the schematic).

It might a good idea to power the unit down, discharge all the caps, pull out V6, then measure the values of R53, R52, R51.  If the values have drifted it might cause problems.

« Last Edit: October 12, 2018, 05:54:03 AM by Rob Strand »
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Rob Strand

Re: help with oscilloscope model 34
« Reply #44 on: October 12, 2018, 05:36:16 AM »
Quote
in the schmatic  v4 is a 6j6  my v4 is a 12au7
in the schmatic v7 is a 12au7  my v7 is a 6x4
will this matter?
Use the schematic you posted.
From what I can see it matches your unit.
The Heathkit schematics I posted are only good to get an idea of the voltages because your schematic doesn't show any voltages.

« Last Edit: October 12, 2018, 05:54:34 AM by Rob Strand »
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whomeno

Re: help with oscilloscope model 34
« Reply #45 on: October 12, 2018, 06:00:55 AM »
ok
R53  27K    34.8
R52  27K     36
R51  10K      11.1

v6
p1 226
p6  224
« Last Edit: October 12, 2018, 06:05:53 AM by whomeno »
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Re: help with oscilloscope model 34
« Reply #46 on: October 12, 2018, 06:46:11 AM »
how close dose pin 1 and 6 need to be?
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Rob Strand

Re: help with oscilloscope model 34
« Reply #47 on: October 12, 2018, 08:24:53 AM »
Quote
ok
R53  27K    34.8
R52  27K     36
R51  10K      11.1

That shows the resistors have drifted quite a bit. Luckily R53 and R52 have drifted equally.
It's not uncommon for old resistors to go off.  What it does mean is there's probably a
lot of other resistors in the unit that have drifted like that and you have to be aware that
the values of resistors might not be what you think they are.

Quote
v6
p1 226
p6  224
Those are quite good readings.

Quote
how close dose pin 1 and 6 need to be?
At one extreme of the horizontal position control you should be able to have one higher than the other at one extreme and at the other extreme the lower one should then become higher than the higher one.  In the middle there is a place where they are about equal.    In other words if you measure the voltage *between* pins 1 and pin 6 you will see a negative voltage, zero voltage, and a positive voltage as you adjust the horizontal position.

The same idea applies with V2 and the vertical position control.  You should measure the resistances R21, R22, R23, R24, R25, R26, R27 to see if there are any way-off resistances.

Once you can get equal voltages on pin 1 and pin 6 of V2 it shouldn't be too hard to get a dot.
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #48 on: October 12, 2018, 02:54:42 PM »
ok I,m back
here is my findings so far
R21 1.2k = 1.26
R22 2.7k= 2.65
R23  1K  =  1.24
R24  5.6K = 5.48
R25  2.7K = 2.60
R26  1K    = 1.26
R27  5.6K = 5.58
v2 pin1 =332   pin6 = 309

could it be the main tube is bad?
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Re: help with oscilloscope model 34
« Reply #49 on: October 12, 2018, 03:18:31 PM »
ok v6 is working fine

now to get v2 going
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whomeno

Re: help with oscilloscope model 34
« Reply #50 on: October 12, 2018, 03:28:25 PM »
ok v2 pin1 =264
 pin6 = 250
but moving switch dose nothing
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Rob Strand

Re: help with oscilloscope model 34
« Reply #51 on: October 12, 2018, 03:53:25 PM »
Quote
ok v6 is working fine
Great.

Quote
ok v2 pin1 =264
 pin6 = 250
but moving switch dose nothing
The thing that changes the voltages on V2 is the Vertical Position pot.

The pot is R19 on the schematic and has four wires.   The middle wire of the group of three pot connections is marked "2" on the schematic.   Make sure there is a wire from Vertical Pot  "pin 2"  to V2 pin 2.
The voltage on V2 pin 2 should vary with the Vertical Postion pot from about 30V to 45V.
The voltage between V2 pin 2 and V2 pin 7 should be adjustable  from -7.5 to -7.5V.
(The voltage on V2 pin 7 cannot be measure directly because the multimeter loading will change the measurement. Also excessive leakage on V2 pin 7 can shift the voltage.)

« Last Edit: October 12, 2018, 03:56:11 PM by Rob Strand »
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whomeno

Re: help with oscilloscope model 34
« Reply #52 on: October 12, 2018, 04:13:38 PM »
ok wire is there to pins 2. switch moves voltage on v2 pin 2
how do i measure pin 7 if i can't do it directly?
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Re: help with oscilloscope model 34
« Reply #53 on: October 12, 2018, 04:15:46 PM »
v2 pin 2 = 34v to 54v
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Rob Strand

Re: help with oscilloscope model 34
« Reply #54 on: October 12, 2018, 04:23:49 PM »
Quote
how do i measure pin 7 if i can't do it directly?
Just measure the difference between pin V2 pin 2 and V2 pin 7; see previous post.
The thing that is important it to get + and - voltage when you vary the Vertical Position pot.

Quote
v2 pin 2 = 34v to 54v
That is probably OK. 
Next do the voltage difference test.
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #55 on: October 12, 2018, 04:30:37 PM »
ok with switch at 0 pin2 54.2  pin7  5.05
switch at 10  pin2  35.3          pin 7   6.6
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whomeno

Re: help with oscilloscope model 34
« Reply #56 on: October 12, 2018, 04:33:56 PM »
R17  3.3m  = 3.7m
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Rob Strand

Re: help with oscilloscope model 34
« Reply #57 on: October 12, 2018, 04:35:53 PM »
Quote
ok with switch at 0 pin2 54.2  pin7  5.05
switch at 10  pin2  35.3          pin 7   6.6
You need to measure the voltage difference by putting the probe on pin 7 and on pin 2 at the same time then measure the voltage with the Vertical Position pot at each extreme.

(Notice that the pin 7 is low because the multimeter loads it down.  To me it looks like it is loading it down a lot.)
The mind often distorts without gain.

Rob Strand

Re: help with oscilloscope model 34
« Reply #58 on: October 12, 2018, 04:37:02 PM »
Quote
R17  3.3m  = 3.7m
That's good to know. It looks OK (yet it has drifted up but the value isn't that critical).
The mind often distorts without gain.

whomeno

Re: help with oscilloscope model 34
« Reply #59 on: October 12, 2018, 04:43:04 PM »
ok    sw on 0   2.0
        sw on 10    it jumps around from -8.0  to -34
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