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Old 08-12-2018, 05:20 PM   #41
neuron
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Quote:
Originally Posted by eccerr0r View Post
Actually measuring the voltage at each H-deflection plate when there's nothing displayed might be interesting.
CRTD1, CRTD2??? R971 and R972
OR Colector T908 and T909

And CRTD3, CRTD4 no interest. ???

CRTG2 +140V?


The -1,9KV any arch ? Distance
And the other 260V ... 140 V? distance

https://en.wikipedia.org/wiki/Paschen%27s_law

https://sciencing.com/calculate-volt...s-8776030.html


" ... debugging my Tektronix 2465 ... "

Can you give details?
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Old 08-12-2018, 06:24 PM   #42
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Yes CRTD1, CRTD2 which are the collectors of T908 and T909.

I currently have absolutely no interest in CRTD3 and CRTD4 because you have yet to do any experiments for us on the V-scale, there is no value on obtaining those readings until you do the V-experiments (i.e. hooking an actual sine wave to the vertical inputs, which you have yet to do). Not only the experiments weren't done, it may end up showing the V-deflection is working just fine and it would be superfluous to list those measurements.

CRTG2 and CRTG1 are unuseful numbers because we see the beam hitting the second anode, implying those values are in range. Again we know the second anode, cathode and grid voltages are within range or at least sufficient enough to display *something* on the screen so we will have to at least assume those are usable to do something for now. It may very well be those voltages are affecting the trace such that it's shrunken down, but we'll get there when we get there, plus unless someone has an identical, working scope to compare with, we have no idea if those voltage values are correct.

Again, do the experiments asked, everything else is on your own to interpret because whatever you do, we don't know what the conditions are that generated that number hence we ask you to do something and get the data that's the result of that thing we asked you to do. Any excess data you post likely will be forgotten/ignored and asked again, do so at that time, it takes less time for us to read one post than have to go through every post again to look for the number we're now interested in.

Please also measure all the power supply voltages and make sure they're within range... this should have been the first step. Fill out the table:

What is the voltage pin
+24V... ____
-12V ... ____
+5V ... ____
+260V... ____ (WARNING! Danger)
+140V... ____ (WARNING! Danger)

Again we have to assume the CRT voltages are correct for now because it lights up green. Better that we don't have to measure them because these are the dangerous high voltages. These voltages would be important if we do not see anything at all on the screen.

My Tek 2465 was acquired broken, and I broke it more when trying to debug it. Eventually I found by step-by-step debug that first I destroyed the CRT by bending the pins too much, then destroyed the vertical amplifier due to an inadvertent short (found by using another scope on the vert amplifier input and output pins) and then found one of the focus amplifiers was nonfunctional - the knob was not working and traced to an op amp that was destroyed due to the initially destroyed CRT. A simple multimeter found that second issue.

Last edited by eccerr0r; 08-12-2018 at 06:34 PM..
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Old 08-12-2018, 07:27 PM   #43
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

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Originally Posted by eccerr0r View Post
Yes CRTD1, CRTD2 which are the collectors of T908 and T909.

What is the voltage pin

+260V... ____ (WARNING! Danger)
+140V... ____ (WARNING! Danger)



My Tek 2465 was acquired broken, and I broke it more when trying to debug it. Eventually I found by step-by-step debug that first I destroyed the CRT by bending the pins too much, then destroyed the vertical amplifier due to an inadvertent short (found by using another scope on the vert amplifier input and output pins) and then found one of the focus amplifiers was nonfunctional - the knob was not working and traced to an op amp that was destroyed due to the initially destroyed CRT. A simple multimeter found that second issue.
Thank you

My problem is if I get burn with this ... volts.

For the +260V +140V I need put the probe there and
then and only then power the Scope?

or we can proceed like +5, +12 V in computers ... no
arc?

And I ask in previous post if I get the probe near
5 ... 10 cm from the tube ... I get an ARC? and
PUFFFFFFFF.

That so talk and no test ...

And The Scope never ... work?
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Old 08-12-2018, 09:20 PM   #44
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

If you're careful you can do it while it's powered up. It would be good to carefully choose a point where you won't slip a probe. You should never get an arc on these supplies, if you do, you probably ruined it. The warning is there so that you don't create a circuit from these points through your body. It's about the same danger as working with mains voltage.

You shouldn't get an arc near the tube either. It should be insulated enough that you can get near it without any worry. In fact usually the chassis around the tube is grounded and the insulation should be strong enough to not allow an arc. If you do get an arc, that's a problem that needs to be fixed. We're not blaming anything yet with the second anode (the big red wire) or the cathode/grid/heater voltage (the back circular plug) so don't worry about it yet. The deflection plates, however, are a symptom that needs to be investigated. Chances are, your deflection plates are hooked up to the back circular plug so I may be wrong on the fact you don't need to touch it, but you can tap off of the collectors of the transistors too. Just treat the voltage with caution. Wrap your multimeter probe tips with electric tape so that only the tips are exposed. Improvise.

My Tek 2465 has separate connections for the deflection plates so luckily I didn't need to touch the back for the deflection testing. But when I didn't get any beam at all, then I needed to check the -2450 volts on the cathode and needed the sole multimeter I had that was 5KV rated: an old analog Eico meter...

Last edited by eccerr0r; 08-12-2018 at 09:28 PM..
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Old 08-13-2018, 03:18 AM   #45
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Don't overlook something non technical. Check for dry or cracked solder joints - especially on components subject to mechanical stress i.e. transistors on the PCB that have a heat sink attached to the chassis, board to board connections. You'll need to clean away the crusty flux to see all the solder joints cleanly but it could be as simple as that.
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Old 08-13-2018, 06:22 AM   #46
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Quote:
Originally Posted by eccerr0r View Post
If you're careful you can do it while it's powered up. It would be good to carefully choose a point where you won't slip a probe. You should never get an arc on these supplies, if you do, you probably ruined it. The warning is there so that you don't create a circuit from these points through your body. It's about the same danger as working with mains voltage.

My Tek 2465 ...
Amazing DataBase !!!

And Tek is Up and Running?


Quote:
Originally Posted by RepairMonkey View Post
Don't overlook something non technical. Check for dry or cracked solder joints - especially on components subject to mechanical stress i.e. transistors on the PCB that have a heat sink attached to the chassis, board to board connections. You'll need to clean away the crusty flux to see all the solder joints cleanly but it could be as simple as that.
Thank you

With Acetone, Benzine, Konkat ...?
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Old 08-13-2018, 09:38 AM   #47
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

with isopropanol
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Old 08-13-2018, 11:05 AM   #48
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

My 300MHz 2465 is working just fine now. Some may find it shocking all I needed was my old 20MHz 'scope.

I used the 2465 to subsequently fix my Tek 2440 which was also acquired malfunctioning ... there were no visually damaged components. Anyway, I tend to try to use the 2440 when it makes sense as it's my only DSO.

To clean flux, it depends on what kind of flux, but be careful with the solvents that destroy plastics.
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Old 08-14-2018, 04:26 PM   #49
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

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Originally Posted by stj View Post
with isopropanol
Clean the front panel - Knobs, Handles, Pulls and Switches what you suggest?



Quote:
Originally Posted by eccerr0r View Post
My 300MHz 2465 is working just fine now. Some may find it shocking all I needed was my old 20MHz 'scope.
And you have videos ?

Or text explan the process ?
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Old 08-14-2018, 07:45 PM   #50
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

No, I don't do videos, the makers never intended me to make videos as I learned in high school. What I've posted in this thread is probably to the extent of any documentation I have about it, and perhaps some other posts I did about it on badcaps.net while I was trying to figure out how to definitively prove I broke the CRT...
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Old 08-15-2018, 04:13 AM   #51
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

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Clean the front panel - Knobs, Handles, Pulls and Switches what you suggest?
no, it could remove the print.

for cleaning circuit boards.
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Old 08-15-2018, 09:32 AM   #52
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

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no, it could remove the print.

for cleaning circuit boards.
bad/dirty contacts,
Inside ... pot, potentiometer ... switch contacts,
carbon pelic.



Thank you eccerr0r
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Old 08-15-2018, 10:50 AM   #53
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

for pots & switches you need contact cleaner
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Old 08-15-2018, 05:33 PM   #54
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

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for pots & switches you need contact cleaner
What you use? brand model

And eccerr0r in 2465 ... Tek 2440?
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Old 08-15-2018, 10:13 PM   #55
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

You need a cleaner AND lubricant.

I am trying Caig DeOxit Fader Lube because it is compatible with conductive plastic and carbon potentiometers.

So far, it works but is expensive and has very little lubricant. I think it's 5% mineral oil. If I spray it on a paper napkin, hard to see any residue there.
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Old 08-16-2018, 06:34 PM   #56
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Yes the two Tek scopes I have are the 4-channel Tektronix 2465 computer enhanced analog and the 2-channel Tektronix 2440 DSO. The 2440 is a primitive DSO with depth of only 1024, but that's the technology that was available then.

As for the contact cleaner you should be able to tell with a multimeter whether you're exhibiting contact problems. And we mean the insides of the pots and switches, not the external appearance of course.
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Old 08-17-2018, 06:33 AM   #57
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Default Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

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Originally Posted by redwire View Post
You need a cleaner AND lubricant.

I am trying Caig DeOxit Fader Lube because it is compatible with conductive plastic and carbon potentiometers.

So far, it works but is expensive and has very little lubricant. I think it's 5% mineral oil. If I spray it on a paper napkin, hard to see any residue there.
Thank you

In local stores:

MOTIP
https://www.motip.com/products/motip...ntact-cleaner/

https://www.wd40specialist.com/products/contact-cleaner

http://cyclo.com/cyclo_product/break...onics-cleaner/ 87

http://cyclo.com/cyclo_product/break...ntact-cleaner/ 85



Any use in your equip.?

Last edited by neuron; 08-17-2018 at 06:34 AM..
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