Display Problem CRT Oscilloscope - Left Side Not Working

[thitou]

Hello everybody !

I have an old Siemens Oscillar D1004 oscilloscope that I am trying to repair  . The whole left side of the screen is not working. As you can see on the pictures, the screen is completely empty on one side.

According to what I read on the internet, it would be bad electrolytic capacitors. I don't have any experience in repairing cathode ray screens, do you think the problem can come from there ?

Any leads to help me identify the problem are welcome!

Here are the photos :



When i press the "beam finder" button, something happen in the "dead" side of the screen :



Try to wire the "1 Vpp"




To have something on the display i need to put the knob with the arrow "<-->" all the way to the left.



This is the inside of it :

is this the electrolytic capacitors for the CRT ?






Thank you for your help ! Any reply will be greatly appreciated 

[jonpaul]

Bonsoir cher Monsieur:

The photos and age lead me to suspect the PSU, check voltages and ripple on all DC PS.

Then the ribbon cables/single line connectors ...easy to have bad /corroded contacts.

00/ Check CRT pins , possible loose or unplugged CRT H déflection plate. 0/ Put contact cleaner on all switches and  exercise.

Put control lube on all pots, exercise.

1/ Loosen and reseat every connector on PCB

2/ Suspect socketed ICs or transistors, loosen and replace carefully

90% of the time this will find the issues.

BON CHANCE !


Jon (6eme)

[thitou]

Bonsoir, merci pour votre réponse rapide !

I will check everything that you have indicated soon as possible.

I hope it's only a bad connection somewhere, maybe an easy fix 

[jonpaul]

Cher Monsieur, je suis l'ancien avec les oscillos, depuis les années 1970.

Si vous habitez près de Paris peut-être possible nous pouvons RDV


Jon

[Chris56000]

Hi!

You can get the technical booklet for the Grundig MO53, which is the same oscilloscope, free from the Internet Archive here :–

https://archive.org/download/grundig_MO53/MO53.pdf

I'm afraid the block diagrams are very faint and the text is all German, but the circuits and PCB layout drawings are all readable!

Unfortunately I'm far too busy with practical repair work @ home to have time to translate and redraw it all, so you'll have to go by the voltage readings in the X amplifier stages and the "X shift" control – check the transistor voltages T15 to T22 on the "Final Amplifier Board" part no.  40011–730.00 !

(If you look at the circuit diagrams carefully there are English translations of the German Technical Terms in smaller lettering below the German ones!)

You might simply have a wire off one of the "X1/X2" side pins on the CRT – this display looks like it !

Chris Williams

[thitou]

Cher Monsieur, je suis l'ancien avec les oscillos, depuis les années 1970.

Si vous habitez près de Paris peut-être possible nous pouvons RDV


Jon

Malheureusement je n'habite pas sur Paris, c'est bien dommage.. Merci quand même pour votre proposition 


Hi Chris, thank you for your help !

I've been searched for those Siemens diagrams without any luck.. Your link for the MO53 clone will be really helpful for sure.

Don't worry about the translation and the redraw ! That's really nice but it's too much work and I really don't want to bother you that much! I'll work out with the German diagrams. My mother is bilingual in German so I may need to ask her 

I will check everything, i really hope that is only a wire that's off somewhere or a bad connection

Good luck with your repairs at home !


Thibault from France

[Wallace Gasiewicz]

Jonpaul has a point. Check the H deflection connections on the tube if there is a tube pin involved, resolder it.
Sometimes there is corrosion at the pin connection inside the base of the CRT tube. The entire black base of the tube can be removed and then reinstalled, but perhaps just clearing out the solder from the H pins and resoldering would help.

[shakalnokturn]

Once you've been through all previous advice. (I'd definitely beware the interconnect on this one.)

PCB's are double sided so bad solders are not so likely, check all the same. Looking at bulky / hot components should give you an quick idea if what to expect.

If all else is good turn to the "endstufenplatte", recheck the +/-15, 50, 130V are getting there.
Then luckily there are some reference voltages on the X-endstufe schematic check those.
If you get to that point my bets are on one of the BF output transistors.

[jonpaul]

Relooking, I think either the CRT left defl plate connection OR hor amp output transistor at negative side.

Easy to check, but you may need a working scope to probe the HOIR amp and delf plates.

Jon