fixing Oscilloscope

File: 20170714_154058.jpg (645KB, 1152x2048px) Image search: [Google]

645KB, 1152x2048px

>>1209221
And the marked points gave not the described Voltage out.

>>1209223
Well, if there's nothing visibly broken... You check whether the fault is before or after that point. For example, if removing all the loads does not help, it's before the point. You continue this way roughly splitting the problem in half in every iteration, until you find the faulty point. Or, if you're feeling lucky, you make educated guesses and test them.

>>1209221

You probably already did this, but I recently "fixed" a 30 year old scope that would not scan horizontally by pulling all the connectors, spraying with contact cleaner, and putting them back on.

And unfortunately one of the best tools besides your multimeter would be a working scope.

>>1209221
power supply failures are pretty common in old scopes.

Look for a service manual online. Any decent scope will have one, even way back into the tube era. If you can't find one for yours, it's either not worth repairing, or going to be a serious pain in the ass to do so.

>>1209223
What voltages were each rail giving?

Without access to an Oscilloscilloscope you are going to have a hard time.

>>1209221

http://www.opweb.de/en/model.php?id=8125

Then click 'Start Free Download'. You now have a service manual with schematics.

You're welcome.

>>1209221
What is the problem? Telling us that would help determine if you're on the right track.

>>1209955
OP here
I think the Voltage Regulator Parts are broke.
>>1209414
and thx a lot for the manual

>>1210916
>I think the Voltage Regulator Parts are broke.

Could be. On equipment of this age, suspect bad caps.

>>1209223
its always the power supply. fix the power supply.

first you should know how power supplies normally work. do you know it?

File: Screenshot - 07202017 - 04:31:44 PM.png (67KB, 888x565px) Image search: [Google]

67KB, 888x565px

>>1212637
>first you should know how power supplies normally work. do you know it?

No, but I want to learn. Are there places on the internet that start with the basics and build up from there?

Something like pic related blows my mind, but apparently it's something of a standard, being as how it's pretty much what is in my Asus 2g surf piece of shit power supply but also shows up in multiple pdfs for the one component that controls the pwm for the main transformer.

I would never have seen this information had not some friendly anon looked at my pathetic photos and description and was still able to point me to the pdf that has this pic, which clarified a lot of things for me.

File: netzteil9v.gif (11KB, 600x450px) Image search: [Google]

11KB, 600x450px

>>1212637
>>1212742
I'm pretty sure how power supplies work, and I'm also sure that it's not a switch mode power supply.Voltage gets stepped down with a voltage regulator.

>>1212742
good switch mode design is a dark art but the basics are pretty simple. there are many good explanations of buck and boost designs, read as many as you can find if you want an education.

from the schematic it clearly is a switching supply with 4 different outputs. the feedback comes from a weird resistor network on both the 5 and 15v rails, look at the very right hand side thet comes out the bottom its marked at 2.5v in a little diamond. this is how the smps chip u401 knows how to adjust itself to get the correct output.
R671 is a potentiometer for calibrating the 2.5v ref voltage. thats the first thing i would check, if that 2.5v is correct then the smps thinks its doing a good job. if the 2.5v is correct but none of the voltages are then adjust the potentiometer until they are correct.

however thats only going to be the problem if its out by a little bit. its very old so likely loads of things are fucked. the psu is the least of your worries.

>>1212839
>from the schematic it clearly is a switching supply with 4 different outputs.

This is what I like about /diy/ trolls. You mix lunacy in with facts.

>>1213098
He's probably referring to the manual >>1209414
posted.
It's for a different scope, though.

>>1213100

Ah. You are correct. I fucked up by treating this thread like a general and injecting an unrelated post.

My apologies to OP and the other guy. I hope OP gets the scope fixed. It isn't that ancient, but it's old enough so that it was made to be repaired. I have a scope I bought in about 85 and the manual contains complete schematics and calibration procedures.

>>1209221
>I think the main problem lays in the power supply
Lucky bastard, my TV's control board broke a month ago and ever since I've been staring at a maze of SMD components with not a hint to go off. There was an 8mm long SMD version of a DIP, it's fucking nuts; I'll never be able to fix it with just my $25 soldering iron even if I can find the broken component.