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Oscilloscope UNAOHM G4020 = BECKMAN 9020 = Voltcraft_2040

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neuron

Hi,
A friend offered
Oscilloscope UNAOHM G4020 = BECKMAN 9020 = Voltcraft_2040

In first hours worked ok ... I saw the 0,2 V 1000Hz
and other signal in the cinescop.

But now I only see 1 or 2 dots (channel 1 or both or ch 2)

I can move the dots UP and DOWN, LEFT and RIGHT
so the screen - cinesc. is working.

I test the trigger, connect CAL 0,2V 1KHz to ch 1 or 2
and the dot go up - down, invert, etc.

A sinos. wave, I can rotate TRIG LEVEL and the dot follow
the wave.
But I can't see the wave in display

Some examples of scope:
youtube.com/watch?v=3nBYp1pN40U

youtube.com/watch?v=fPq1KgQ5ggQ

youtube.com/watch?v=5osskamWJHg

Manual and schemat. I have the French and Germany version.

archive.org/details/voltcraft_Voltcraft_2040_Oscilloscope_Service_manual

https://elektrotanya.com/beckman...

Can you please provide help?

Thank you,

Ruy

Comments
neuron

Thank for your info

The +260V -> +301V

Repaired and test all other Volts.

I have Brymen ... and will proceed with more test

Any advice is welcome.

Best Regards,
Ruy

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Ferenc.P

Hi!
Hmm, the lower side is floating, the -12V is missing...

Best Regards!

File csatolás: 

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neuron

Hi Ferenc,

The +24 ... minor float and

Volt in T908 and T909
5X - 2XX
and 2XX - 6X

please explain.
Ruy

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Ferenc.P

Hi: It is noticeable that on schematic (drawing) is missing the negative supply (-12V) value.

"Volt in T908 and T909
5X - 2XX
and 2XX - 6X"

Their values looks good, but as You have already mentioned, you checked it.

All the best, Feri

File csatolás: 

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Edmundson
Edmundson's picture

Hi neuron!

Do not use WD40 in electronics because that is an oil based substance. Use isopropyl alcohol or Kontakt WL.

Could you please take a video about the issues because sometimes is not clear. Upload it to Youtube or your cloud.

If you have a dot instead of line is very important to know where is it located. If it lit on the left side of the screen means the trigger signal is missing. It the dot is in the middle of the screen means the horizontal deflection (or timing south wave signal) is missing.

If you can move the dot from the left side to the right side of the screen (reel-to-reel) with the X-POS pot means the X deflection power amplifier is working.

So I think we need more precise information to be able to help.

BR

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Ferenc.P

Hi Ruy!
At the beginning the "X-Y" switsch must be on "Y" pos.
Is this setting on right position?
If YES then the problem is mainly in TIME-BASE generator (page 41 from Your linked file) or in triggering/SWEEP GENERATOR stages: if the trigger signal missing, the Time-base generator will not start particularly in NORMAL mode.

Sorry for grammar...

 I have (some) scanned pages from english user manual. If You can not find it elsewhere, I will upload it.

Best regards, Feri

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neuron

>Hi Ruy!
>At the beginning the "X-Y" switsch must be on "Y" pos.
>Is this setting on right position?
>If YES then the problem is mainly in TIME-BASE generator (page 41 from Your linked file) or in >triggering/SWEEP GENERATOR stages: if the trigger signal missing, the Time-base generator will not start >particularly in NORMAL mode.

Thank you your info,

I have other Scopes ... I have experience ... NO that's not the problem.

TimeBase or Trigger - with another Scope I can see (different Time/Div settings)
the Sawtooth in R6001, R6002, R961 and T908.
And we can see the changes HoldOFF and CAL.

> I have (some) scanned pages from english user manual. If You can not find it elsewhere, I will upload it.

I posted the link - Service Manual - BECKMAN 9020
German - Voltcraft_2040.

I have the French Version too.

With a Time/Div we can see a dot.
If we set a smaller Time / Div we get a comet.
With a sinos. wave we see the initial start of the wave and then disappear the rest of wave.

I try Upload JPG ... but exceed the 3 MB

Best Regards,
Ruy

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Ferenc.P

Hi Ruy!
Please, can You check the blanking pulse changing? ...only because of lighter search: start measure, for example from R734.

Best Regards, Feri

 

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neuron

>Hi Ruy!
>Please, can You check the blanking pulse changing? ...only because of lighter search: start measure, for example from R734.

>Hi Ferenc,

>Yes and R552, T507 .. but only in a few days, the scope in another warehouse.

Tested -> OK :-)

Please can you describe further info ... this spot?

Best Regards,
Ruy

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Ferenc.P

Hi!
So:
- "I can move the dots ..., LEFT and RIGHT".
   On full display width? 
   Is the X-FINAL amplifier tested, as good?
- "...see the initial start of the wave and then disappear the rest of wave"
   Is it sudden or gradual?

Best Regards, Feri

 

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neuron

Hi Ferenc,

>So:
>- "I can move the dots ..., LEFT and RIGHT".
> On full display width?
> Is the X-FINAL amplifier tested, as good?

Yes
From LEFT to RIGHT and RIGHT to LEFT

The volt in T908 and T909
5X - 2XX
and 2XX - 6X

> - "...see the initial start of the wave and then disappear the rest of wave"
> Is it sudden or gradual?

I see a comet.
If you observe a sin or a square ... we saw the first rise, no initial plateau (no fall) ... disappear the rest to the right.

The noise ( 220V ) from the house circuit ... we see lots of dots - vertical.

Best Regards,
Ruy

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Ferenc.P

Hi: In my opinion, the blanking circuit will remain to need check.
I mean, The "chopped blanking" from Y-stage (IC401 thru) and from the above mentioned line R734 too.
Both, to the CRO-cathode.

Best Regards, Feri

(As you know, special attention is needed for measurements around the IC506.)

 

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neuron

> Hi: In my opinion, the blanking circuit will remain to need check.
> I mean, The "chopped blanking" from Y-stage (IC401 thru) and from the above mentioned line R734 too.
> Both, to the CRO-cathode.

Thank you very much for your info.

1 - The procedure is select CHOP in front panel and ... ?
C555, R553

De-select CHOP ? observe the signal?

2 - I don't have a 2000 V Probe. So I can't R575, R576 ( -1867V ) arc?
and R574 any problem?

3 - Clean the VR567 with Kontakt, WD40 Specialist or ... ?

You work with Scopes and DMM ?

Best Regards,
Ruy

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Csu

Hi Ruy!
” 2 - I don't have a 2000 V Probe. So I can't R575, R576 ( -1867V ) arc?
and R574 any problem? ”
to fix this problem You ca build an 10:1 attenuator, or maybe better  100:1 by replaceing 9Mresistor to 99M

Regards
Csaba

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Kari

Ruy,
in my opinion WD40 has to banned from (fine) electronics!
Use please only right one Kontakt sprays-or similar brands...
Kari

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neuron

Kari,

Not that one for Car and Bic.
Please read:
https://www.wd40specialist.com/p...

http://kontaktspray.hu/en/?Products ?

And what are your suggest?

Any other brand for the knobs in front panel?

Kind Regards,
Ruy

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Kari

You see,
I do know only the classic WD40 and its agressive for electrical cards, caused after some time corrosive problems & advertisings are not 100% to belive-or you can?
You`r linked Kontakt Chemie_one of the best addresse- (check Kontakt-60/WL/601 & Tuner-60 for RF parts_what are best for you) burt they are other good brands too as CRC and so on...
Kari

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neuron

Thank you for your info

> Kontakt-60/WL/601 & Tuner-60

Pots. - 601 and Tunner 600 is best ... WL don't think is ok ... is for corr. contacts

>Hi Ruy!
>” 2 - I don't have a 2000 V Probe. So I can't R575, R576 ( -1867V ) arc?
>and R574 any problem? ”
>to fix this problem You ca build an 10:1 attenuator, or maybe better 100:1 by replaceing 9Mresistor to 99M

All my Scope probe are 600 V and the plastic and wire ... not rated for this Volts.
Arc everywhere ...

and Cap?

The tip is very thin, we need a large fat tip

Regards,
Ruy

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Csu

Hi Ruy!
"All my Scope probe are 600 V and the plastic and wire ... not rated for this Volts.

Arc everywhere ...

and Cap?"
I used this type of attenuator to measure the HV source of an oscilloscope.
At 2KV, it is unlikely to arc. I had built this type of attenuator on a perfboard.
For Your current application (it doesn't have to be too accurate),  this type should be good enough, it should work fine without compensation, but if You would like to build a precise one, here is one circuit:
High-voltage-10to1-R-divider.gif
The link below has the description.
http://www.turneraudio.com.au/Vo...
Regards
Csaba

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neuron

Thank you for your info

>Do not use WD40 in electronics because that is an oil based substance. Use isopropyl alcohol or Kontakt >WL (link is external).

https://www.wd40specialist.com/p... and this one too?

Kontakt WL very corr.? and don't think is a good idea in Pots

I only use Kontakt ... any CRC?

>I used this type of attenuator to measure the HV source of an oscilloscope.
>At 2KV, it is unlikely to arc. I had built this type of attenuator on a perfboard.
>For Your current application (it doesn't have to be too accurate), this type should be good enough, it >should work fine without compensation, but if You would like to build a precise one, here is one circuit:
>High-voltage-10to1-R-divider.gif
>The link below has the description.
>http://www.turneraudio.com.au/Vo...

Very info ...

Regards,
Ruy

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neuron

Hi,

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neuron

>Their values looks good, but as You have already mentioned, you checked it.

>All the best, Feri
>File csatolás:
>schem_.pdf

Amazing !!! :-) :-)

Your design?

Best Regards,
Ruy

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