Hi everyone!
I've got a bit of a problem with an oscilloscope i obtained from a technical college. This 'scope was one of eight decommissioned probably a year or so ago, and has been tampered with by students (part of an assessment...).
I asked my lecturer if i could take one home and fix it, as i NEED an oscilloscope on my test-bench quite desperately, but have no money to buy one.
With permission, i proceeded to test each one only to be met with blank screens, funny sounds and general all-round failure.
One of the 'scopes still (half) worked, i could basically get it to display a trace.
So i told my lecturer, and he tested the oscilloscope: he tweaked a few things and the oscilloscope was pretty much fine: except for a sticky button.
He tried ramming the button to make it return, but that did nothing, and the whole thing went dead.
I took the 'scope home and pulled off the cover to check the insides.
I found many issues, such as a completely dislocated PCB, a bunch of loose screws, and the 'sticky button' was not toggling because of a capacitor which was bent into the path of the button-shaft.
I also found that the 7915 regulator's tab was NOT isolated from the chassis, which is why the random failure.
So i replaced the regulators, a few caps, and isolated the tab of the new 7915, and viola! it worked!
And that is where i'm at now.
What i got when i powered up my 'fixed' oscilloscope was a green power LED, but absolutely nothing on the screen. I tried meddling with every control, all to no avail.
I applied +12V to the Z-input on the back, and i got a funny elongated dot-thing up top of the screen. Messing with the vertical alignment, focus and magnification controls caused movement, but the intensity control did nothing.
From researching everything i could, i figured that the problem lied within the horizontal amplifiers, so today i found some replacement chips and installed them. Didn't work much wonder at all, in fact the funny dot i got from the Z-override does not show up now, but if i power the 'scope up with the override voltage present i get a flicker of what looks like a trace, which darts off slightly to the right, then shoots straight up and off-screen.
Other than that, nothing.
My oscilloscope is the BWD instruments BWD820.
I found the manual here
EDIT: schematics from page 57 in manual - saves a little time
If anyone has an inkling if an idea what the problem is, any help is greatly appreciated
I've got a bit of a problem with an oscilloscope i obtained from a technical college. This 'scope was one of eight decommissioned probably a year or so ago, and has been tampered with by students (part of an assessment...).
I asked my lecturer if i could take one home and fix it, as i NEED an oscilloscope on my test-bench quite desperately, but have no money to buy one.
With permission, i proceeded to test each one only to be met with blank screens, funny sounds and general all-round failure.
One of the 'scopes still (half) worked, i could basically get it to display a trace.
So i told my lecturer, and he tested the oscilloscope: he tweaked a few things and the oscilloscope was pretty much fine: except for a sticky button.
He tried ramming the button to make it return, but that did nothing, and the whole thing went dead.
I took the 'scope home and pulled off the cover to check the insides.
I found many issues, such as a completely dislocated PCB, a bunch of loose screws, and the 'sticky button' was not toggling because of a capacitor which was bent into the path of the button-shaft.
I also found that the 7915 regulator's tab was NOT isolated from the chassis, which is why the random failure.
So i replaced the regulators, a few caps, and isolated the tab of the new 7915, and viola! it worked!
And that is where i'm at now.
What i got when i powered up my 'fixed' oscilloscope was a green power LED, but absolutely nothing on the screen. I tried meddling with every control, all to no avail.
I applied +12V to the Z-input on the back, and i got a funny elongated dot-thing up top of the screen. Messing with the vertical alignment, focus and magnification controls caused movement, but the intensity control did nothing.
From researching everything i could, i figured that the problem lied within the horizontal amplifiers, so today i found some replacement chips and installed them. Didn't work much wonder at all, in fact the funny dot i got from the Z-override does not show up now, but if i power the 'scope up with the override voltage present i get a flicker of what looks like a trace, which darts off slightly to the right, then shoots straight up and off-screen.
Other than that, nothing.
My oscilloscope is the BWD instruments BWD820.
I found the manual here
EDIT: schematics from page 57 in manual - saves a little time
If anyone has an inkling if an idea what the problem is, any help is greatly appreciated