Broken Scope -- help?

[longano]

greets all,
don't know if i'm in the right group.

thought i purchased a 120/220V oscilloscope
(Tenma)

blindly plugged it into a 220V line and
it made a heartwrenching sound.

now all i get is two little dots in the middle of my screen. focus and intensity controls still work.. but thats about it.

fuse is fine, of course.

what did i burn? anyway i can fix this myself? (without the aid of another scope)

thanks,
-longano

 

[nbucska]

If you have to ask, most likely not.

<nbucska@pcperipherals.com>

 

[longano]

i was hoping someone could tell me where i most likely caused damage.

a powersupply i can fix.
a blown tube is a different story.

-longano

 

[nbucska]

The basic problem is that I never heard about TENMA--
it looks like there is a design error, the fuse and
other protection should have prevented the damage.

Repairing an unknown instrument is not a trivial task.

<nbucska@pcperipherals.com>

 

[cbarn24050]

Hi, its most likely to be the power supply.

 

[david707]

You don't say whether it is a digital or analogue scope. If it is analogue , the fact that you have an electron beam is evidenced by the spot(s) on the screen. It certainly means that there is no timebase operating although tubevoltages may be OK. In view of what you have done in terms of connecting the wrong mains supply, damage to the power supply unit is most lekely. Do you have a circuit diagram available? A few checks around with a voltmeter would be revealing, but cct diagram essential.
More data please.
Best wishes,
David707

 

[automatic2]

Sounds like one (or more) of your power legs is out. get your hands on the schematics and verify each leg. When you find the one that's not to spec, isolate and troubleshoot. Shouldn't be too hard. You could always take it back and say it doesn't work (on warranty).

 

[joaco1]

If your scope says Tenma 72-300 in the front Panel, I own the same.

Bought it 18 years ago in te States for hobbying, still have it working.
If you want, Send me your fax and I can fax the manual with the schematics.

joaco1