Oscilloscope UNAOHM G4020 = BECKMAN 9020

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Well now that we know there's traces or dots on the screen, you don't need to mess with the cathode or anode voltages, do not touch them, stay away until we know otherwise. The deflection grid plates can get to 100-200V so they're not a walk in the park, just be diligent and take all necessary precautions working with high voltages. I survived debugging my Tektronix 2465 high voltage board, anyone else can too.

I'm debugging this methodically, if you want to test the ICs before knowing where to search for problems, go ahead, but it wasn't my plan yet.

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

R6001, R961, and T908 are on the X final board...

If you see HG1 voltage changing with the battery voltage, then I'd suspect T908 first but check all three.

Thank you,

I have the DMM in another loc. in 2 or 3 days ...

Test -> T908 and other T. with Diode mode.

You test with R - Ohm and values I expect?

Caps with ESR

The ICxxx - 7474, 74122, 7812, 4011 ... test?

If I test the Volts in CRTD1, CRTD2, CRTD3, CRTD4,
CRTG2
any danger the -1,9KV or the 2KV or -1867V ... get in that lines ?

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

R6001, R961, and T908 are on the X final board...

If you see HG1 voltage changing with the battery voltage, then I'd suspect T908 first but check all three.

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Ok this test should definitively split the search space:

Put your DMM on the HG1 connection.

Put your scope in X-Y mode and set the attenuator to 100mv/div.

Then connect a 1.5V battery to the X input (II?) and record the voltage. Then swap the + and - to the battery, and note the voltage again.

If the two are the same, then the problem is not on the X final board.

---

Heh, quote from manual:

And R6001, R961 and T908?

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Ok this test should definitively split the search space:

Put your DMM on the HG1 connection.

Put your scope in X-Y mode and set the attenuator to 100mv/div.

Then connect a 1.5V battery to the X input (II?) and record the voltage. Then swap the + and - to the battery, and note the voltage again.

If the two are the same, then the problem is not on the X final board.

---

Heh, quote from manual:

Notes:
If the 9020 is turned on while the component test
button is depressed, it will appear to be "dead."
To restore normal operation, press and release
the component test button.

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Okay... so your the time/division knob makes no difference or is this the only setting that you get a little bit of trace?

TIME / DIV is 5us, 10us - trace ( tail ) with 1 cm.
Ruy_20180801_114927.jpg
Other ... dots

And if you add in a Y-signal does it do anything?

https://www.badcaps.net/forum/showpo...98&postcount=8

In 3)

And if in XY-mode you get nothing at all? Even with beamfinder and rotating the XPOS and YPOS pots? And the XPOS you have pulled out too?

Noooooo

BTW, HG1 is the blue wire on mid/left of 20180803_103917.jpg it appears. How much of a change does disconnecting it do (do you get a dot instead of the lines?). I would probably start looking at this board for more clues but I have not ruled out other boards. This is the X final.

ok

Best Regards,
Ruy

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Okay... so your the time/division knob makes no difference or is this the only setting that you get a little bit of trace?

And if you add in a Y-signal does it do anything?

And if in XY-mode you get nothing at all? Even with beamfinder and rotating the XPOS and YPOS pots? And the XPOS you have pulled out too?

BTW, HG1 is the blue wire on mid/left of 20180803_103917.jpg it appears. How much of a change does disconnecting it do (do you get a dot instead of the lines?). I would probably start looking at this board for more clues but I have not ruled out other boards. This is the X final.

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Which settings go with which picture, and you have NO external input?

So you're saying "tall" when the picture shows "wide" ... This is why I'm confused!

T A I L - not ... tall heheheh

Ruy_20180801_114927.jpg -> Ruy_20180803_123303.jpg

NO external input



" ... a good clean is an idea, there are solder balls and splats all over the underside of that board!! ..."

And your sug. is? Procedure ?

This is dated 1988 so the electrolytic capacitors look pretty old. If there is AC hum, the ripple would make the trace/dot into a bar.

I would check the +140VDC rail, and filter cap C524 47uF 250V, used for both the CRT X (horiz) AND Y (vert) deflection amps, and is part of the +260V rail.
I would check the +260VDC rail, and filter cap C523 47uF 250V, used for the CRT X (horiz) deflection amps.

Thank you I will check.


For my data base can you please give other examples ...?
in future if I have other scope ... I know the problem ...

Thank you
Ruy

[redwire]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

This is dated 1988 so the electrolytic capacitors look pretty old. If there is AC hum, the ripple would make the trace/dot into a bar.

I would check the +140VDC rail, and filter cap C524 47uF 250V, used for both the CRT X (horiz) AND Y (vert) deflection amps, and is part of the +260V rail.
I would check the +260VDC rail, and filter cap C523 47uF 250V, used for the CRT X (horiz) deflection amps.

[stj]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

a good clean is an idea, there are solder balls and splats all over the underside of that board!!

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Which settings go with which picture, and you have NO external input?

So you're saying "tall" when the picture shows "wide" ... This is why I'm confused!

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Okay, wait. Now I see horizontal lines. This means that the horizontal amps and oscillator is trying to do something. What are the settings and input that generated this picture? This is why if it's possible I'd like to see the picture of the scope's screen output AND the settings of the scope at the same time, with pictures of probes hooked up to the inputs. This would help rule out communications issues when typing in descriptions of what you see.

Now what I don't know is if the vertical amplifiers are working since we are seeing horizontal lines.

After reporting what are the settings and input that described how you got those horizontal lines shown, can you move those lines left/right and up/down, all the way, with the X-pos and Y-pos potentiometers. Also what happens when you add in a sinusoidal Y-input from the attenuators if you aren't already (set input to say 10mV and touch the pin of the probe).
Then take a picture if it changes from the shown picture.

Also while you're at it: measure all power supplies except the CRT second anode and CRT cathode voltage. You may have a weak power source that would explain both X and Y issues if you indeed have both issues. I ask not to measure the CRT second anode and cathode voltages because these are likely several thousand volts, and most people don't have the equipment to safely measure these.

(unrelated to the scope, just beef about cameras:
Also another thing I wish people had the capability of doing: using a tripod and making long exposure shots of the screen. It's an advanced photography technique that many cell phones can't do - in the realm of requiring DSLRs or at least better software/hardware that allows turning down the camera's sense amplifiers...)

The settings:

https://www.badcaps.net/forum/showpo...2&postcount=11

https://www.badcaps.net/forum/showpo...8&postcount=14

TIME / DIV is 5us, 10us - trace ( tail ) with 1 cm.


" ... can you move those lines left/right and up/down, all the way, with the X-pos and Y-pos potentiometers. ..."

YESSSSSSSSSSSSSSSSSSSSSSS
I explained in previous post

"... CRT second anode and cathode voltages because these are likely several thousand volts ..."

-1867 V
1,9KV


Best Regards,
Ruy

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Okay, wait. Now I see horizontal lines. This means that the horizontal amps and oscillator is trying to do something. What are the settings and input that generated this picture? This is why if it's possible I'd like to see the picture of the scope's screen output AND the settings of the scope at the same time, with pictures of probes hooked up to the inputs. This would help rule out communications issues when typing in descriptions of what you see.

Now what I don't know is if the vertical amplifiers are working since we are seeing horizontal lines.

After reporting what are the settings and input that described how you got those horizontal lines shown, can you move those lines left/right and up/down, all the way, with the X-pos and Y-pos potentiometers. Also what happens when you add in a sinusoidal Y-input from the attenuators if you aren't already (set input to say 10mV and touch the pin of the probe).
Then take a picture if it changes from the shown picture.

Also while you're at it: measure all power supplies except the CRT second anode and CRT cathode voltage. You may have a weak power source that would explain both X and Y issues if you indeed have both issues. I ask not to measure the CRT second anode and cathode voltages because these are likely several thousand volts, and most people don't have the equipment to safely measure these.

(unrelated to the scope, just beef about cameras:
Also another thing I wish people had the capability of doing: using a tripod and making long exposure shots of the screen. It's an advanced photography technique that many cell phones can't do - in the realm of requiring DSLRs or at least better software/hardware that allows turning down the camera's sense amplifiers...)

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

In pag. 54 R410 +24V EXT S601

In page 55 HG1 GB S601
to 56 SWEEP SIGNAL T703

More JPG to analyse

Regards,
Ruy

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Doesn't matter what the Y source is, you could set your input attenuators to 10mV and touch your fingers using the highly prevalent line frequency noise that should be everywhere if you're in an urban or suburban environment.

Depending on the edge rate of the calibrator output vs you time/division, you may just get two dots...

Thank.

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Doesn't matter what the Y source is, you could set your input attenuators to 10mV and touch your fingers using the highly prevalent line frequency noise that should be everywhere if you're in an urban or suburban environment.

Depending on the edge rate of the calibrator output vs you time/division, you may just get two dots...

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

If you can move the Y pos pots and its respective dot can be moved up an down, it demonstrates quite a bit is working - multiplexer is working, and yes, the Y finals are working. Doesn't show much about the preamp condition.

But what can you do with the X position, from the front panel, anything at all?

If the trace that would have shown a vertical line off screen is brought to the center with beamfinder, then you would be able to see it with beamfinder depressed. It's just proof that the vertical input amplifiers are working too.

" ... say you can move the X dot from left to right with the X pos potentiometer, so the X amplifier is working ..."



With the CAL signal?
I will test

" ... still waiting for picture upload."

working

Best Regards,
Ruy

[stj]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

still waiting for picture upload.

[eccerr0r]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

If you can move the Y pos pots and its respective dot can be moved up an down, it demonstrates quite a bit is working - multiplexer is working, and yes, the Y finals are working. Doesn't show much about the preamp condition.

But what can you do with the X position, from the front panel, anything at all?

If the trace that would have shown a vertical line off screen is brought to the center with beamfinder, then you would be able to see it with beamfinder depressed. It's just proof that the vertical input amplifiers are working too.

[neuron]

Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

Show a photo of the insides to us, I picked out one wire from the schematic, perhaps we can find that wire in a picture for you to inspect, at least visually, if you don't have another scope to check it.

But wait, you say vertical amplifier is OK, so if you feed in an AC to the vertical inputs, you should be able to see a vertical line, perhaps requiring the use of the beamfinder button. If you're not getting any vertical line with an AC input, then we have some strange dual failure that my be just a switch problem.

This is great ... Thanks.




" ... say you can move the X dot from left to right with the X pos potentiometer, so the X amplifier is working ..."

I can move CH 1 and Ch 2 dot up and down with the Y POS I, II potentiometer, I deduce
"Vertical Final Amplifier is ok" ?


" ... the use of the beamfinder button." Please explain.

Regards,
Ruy