Distorted oscilloscope trace

Hi Check bypass electrolytics. It looks like the axis are cross talking through the supply lines. Dwight

I strongly suspect power supply problems. Check for bad power supply filter capacitors. These are typical causes of distorted and fuzzy traces on a scope. As I remember, this model scope isn't particularly easy to disassemble and repair, so get ready for some bench time. If you have or can borrow another scope, that will make your troubleshooting a LOT easier. If you don't have a service manual, you really should get one. You can buy a digital copy from

for $10.00. Artek sells high quality scanned copies; I can recommend them from personal experience. Cheers!

--
HAM AND EGGS -- A day\'s work for a chicken, a lifetime commitment for a pig.

Dave M

Tubes busted internally, if it was signal distortion the shape would be the same top, bottom or middle of the screen.

You will most likely here glass tinkling inside the tube if you tip the scope, also remove the blue implosion filter and check for tiny marks on the phosphor from debris. JC

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You must get another scope and see if there are signals getting to the CRT deflection plates when the input is grounded. Bad electrolytics are the most likely problem!!! But, a scope is the only way to tell for sure.

Tubes busted internally, if it was signal distortion the shape would be the same top, bottom or middle of the screen.

You will most likely here glass tinkling inside the tube if you tip the scope, also remove the blue implosion filter and check for tiny marks on the phosphor from debris. JC

In fact unless your filter is dirty, I can see pock marks on the phosphor behind the filter, there should not be any marks at all.

JC

Yes you're spot on, I disassembled the tube to check if any damage was visible, and there were little pieces of glass going around inside. One of the glass posts holding the deflectors and electron gun was broken. There are indeed several marks on the phosphor, as if it was scratched from the inside.

Out of curiosity, do you know what element in particular causes the strange distorsion ? Since the shape changes whith the y-position, I figure this would have to be after the vertical deflection plates, but I don't see what it could be.

v.

In this case shouldn't the distorsion be the same whatever the y-position is ?

I have another scope (which I hoped to slightly upgrade), so I'll do as you suggest and check the signal on the vertical deflection plates, to be sure.

v.

No, never really looked into it, buying scopes off Ebay if the seller doesn't pack the scope well (assuming it was ok before) then this is the result. I bin a dozen tubes a year, basically that's a dozen scrap scopes as tubes are unavailable.

Did the auction listing show a trace when you bought it? If it was a straight line or undistorted waveform then damage occurred in shipping and you could file SNAD with Paypal.

JC

vic wrote in news:4a0493a2$0$6733$ snipped-for-privacy@news.free.fr:

Oh,yes,seen lots of them. I worked for TEK 21.5 yrs,Indy and Orlando service centers.

don't be so sure;Ebay or Sphere in Canada may have parts.

IMO,the CRT is toast;judging from the bent trace and glow on the left side of the graticule.But you should check the power supplies anyways. That's always step ONE.

FYI,checking tube geometry is best done with a signal displayed. Then you can see the vertical distortions.

If you do remove the CRT,tilt it and see if you hear little bits tinkling inside,that's from the electron gun glass rods that got cracked.Sometimes you can see them on the faceplate,or they make spots on the graticule.

--
Jim Yanik
jyanik
at
kua.net

vic wrote in news:4a04bf89$0$3099$ snipped-for-privacy@news.free.fr:

It could be the final mesh screen,and/or any one of the defelection plates.

--
Jim Yanik
jyanik
at
kua.net

Regardless, it is a firm eBay rule that if the item is damaged in shipping, regardless of the circumstances, it is 100% the seller's responsibility. The seller cannot disclaim shipping damage, nor can a seller *require* shipping insurance as a seperate item conditional on the sale.

Title doesn't pass to the buyer until the item arrives "in the buyer's hands in the condition described". So simply file an eBay/PayPal claim and be done with it.

It is the seller's problem, not yours. Don't let him tell you otherwise.

They do neither offer a phone number nor their location. And their Web-Site seems to be broken (with Firefox 2).

Regards, H.

How would you prove, as a buyer, that you didn't drop it yourself after having received it?

Regards, H.

OMFG WTF Here we go again

JC

I never buy from this kind of shop since their business model seems dodgy to me. Basically they sell copyrighted works of others, and stuff that is sometimes freely available elsewhere.

v.

Paypal and Ebay assume it's the seller's fault unless the seller can prove otherwise. The buyer will probably have to return it as his own expense, but he should receive a full refund from Paypal (including the original shipping charge).

The first step is to politely contact the seller. Most sellers are reasonable and honest. Andy Cuffe

snipped-for-privacy@gmail.com

The auction did not show the oscilloscope in operation, however the description said that it was in working condition. While technically it does operate, that's not what I consider working condition. I only paid

40 euro though, so I think I won't bother with the procedure, especially if I have to send it back to the seller, with proper packaging this time. I'll probably save some more and buy a recent model one day.

Cheers.

v.

Just to give some feedback, I tested the deflection plate voltages and power supply and they look correct to me. So I'm a bit pissed off that an otherwise working device was destroyed by careless handling on the part of the sender. I guess my current very old, unreliable and completely decalibrated oscilloscope will have to do a little longer :-)

v.

I would suggest taking a series of photographs of the scope, and all of the packing materials.

If the scope was not packed very well indeed (if e.g. it was just thrown into an outer carton full of styrofoam peanuts), the photos would be useful evidence in showing that either:

- the packing materials weren't really up to the job, or

- the packing was OK, but the carton shows evidence of real physical abuse by the shipping/freight company. In both of these cases, it's legally the seller's responsibility to deal with the issue. The shipper will *not* talk about insurance or reimbursement with the addressee, since the contract for shipment (and any contract for insurance) was with the seller.

My understanding of Federal law, is that it agrees with what you're saying of eBay/PayPal policy. When you buy something by mail, it's the seller's legal responsibility in most cases to get it to you in good physical condition.

--
Dave Platt                                    AE6EO
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