Instructables

Oscilloscope PSU whining noise?

My oscilloscope is a Philips PM3055. It's a CRT type with a modular internal design, one PCB is the PSU, one is the front panel, a few are TTL, etc.
When I try to turn it on the screen is blank and the PSU makes a whining/whistling noise, and does not function.
The whining persists regardless of connection to other boards and mains ground.
(mains ground is normally not connected to the PSU, but there's a connector)
I have found no bulging/leaking capacitors (though I have no way of testing capacitance) or other visible damage,
except for cracked plastic on the front panel. But that's merely cosmetic.

Replacing the PSU is not an option, since the scope is old and obsolete. Neither is buying a new scope. I am broke.

All help greatly appreciated!
If you help me fix it, I might just send you one of those fancy patches.

I can only provide cellphone-camera quality pictures at the moment, and for that I am sorry.

[Edit / update]
I contacted Advance Product Services, And they sent me the complete service manual for the scope, free of charge.
Those guys are awesome!

seandogue2 years ago
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Kirbsome! (author)  seandogue2 years ago
I'll keep that in mind.
The reply issue might be because the post tree reached a limit?
Anyway, thank you for all your help. Although the problem isn't yet completely solved yet, I keep my hopes up. Consider yourself patched.
seandogue2 years ago
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Kirbsome! (author)  seandogue2 years ago
Thanks.
This will take time, as there's a ton of them. And it's hard to see on these axial ones.
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Kirbsome! (author)  seandogue2 years ago
The ear-straw noise listening while out of shell and powered on
(damn that's a hard sentence)
was the first thing I did, hence the marked "General area where whining occurs"
Something about having a clear PVC tube in your ear really reduces your dexterity,
and that's why the area of the whine is so vague. But I'll see if I can find a computer mic.
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Kirbsome! (author)  seandogue2 years ago
The two big blue electrolytic cans are just plain wierd. They have three leads each, and indentations in the sides giving them a shape kind of like a torx. The bulging on the top is real, but not nearly as pronounced as in the picture. I think it's just its normal shape, since no leaking or deformation in the sides is visible.
The yellow hexagonal doohickey is what appearst to be a dual inductor.
(Not a transformer, since it's marked "2x10mH")
Lastly, and sadly, no. There's no one I can borrow test equipment from that I know. It's hard being a geek in a small town...
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Kirbsome! (author)  seandogue2 years ago
They both have the slight bulge on top, between 1/3 and 1/2 millimeter in height.
Wouldn't the sides be the first thing to "pop out" on these though?
DSC01055.JPG
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Kirbsome! (author)  seandogue2 years ago
A university is a great idea, too bad none are close here.
Though, I'm moving far away for high school in a couple weeks.
(it will be awesome, they even offer courses in soldering!)
Maybe I should just wait until then, and try finding a decent workshop there?
kevinhannan2 years ago
hmmm.....high-pitch whining usually comes from my wife - taking my hearing-aid out usually fixes it! ;-)
Is this just the HT supply for the tube or the PSU for the whole thing ?
Whatever, have you got a good voltmeter ?
Steve
Kirbsome! (author)  steveastrouk2 years ago
It's the PSU for the shebang. I have a voltmeter, but I don't know what the voltages are supposed to be.
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