Distorted oscilloscope trace

[vic]

Hi,

I recently bought an oscilloscope on eBay, and I don't know if the
seller lied in the description or if it was damaged during the
transport, but the trace is completely distorted and shows strange
grid-like patterns. I made a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the
tube ? Could it have been damaged if the oscilloscope received a shock
for example ?

I think the tube is pretty much toast, as well as the scope since there
is no way I could find a replacement tube (Tektronix 2225), but I
wouldn't mind to be proven wrong Thanks.

 

[Dave M]

"vic" <news@bidouille.org> wrote in message
news:4a0493a2$0$6733$426a74cc@news.free.fr...

Hi,

I recently bought an oscilloscope on eBay, and I don't know if the seller
lied in the description or if it was damaged during the transport, but the
trace is completely distorted and shows strange grid-like patterns. I made
a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the tube
? Could it have been damaged if the oscilloscope received a shock for
example ?

I think the tube is pretty much toast, as well as the scope since there is
no way I could find a replacement tube (Tektronix 2225), but I wouldn't
mind to be proven wrong Thanks.

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 http://artekmed.startlogic.com/page2.html 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

 

[Archon]

Dave M wrote:

"vic" <news@bidouille.org> wrote in message
news:4a0493a2$0$6733$426a74cc@news.free.fr...
Hi,

I recently bought an oscilloscope on eBay, and I don't know if the seller
lied in the description or if it was damaged during the transport, but the
trace is completely distorted and shows strange grid-like patterns. I made
a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the tube
? Could it have been damaged if the oscilloscope received a shock for
example ?

I think the tube is pretty much toast, as well as the scope since there is
no way I could find a replacement tube (Tektronix 2225), but I wouldn't
mind to be proven wrong Thanks.

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 http://artekmed.startlogic.com/page2.html for $10.00. Artek sells high
quality scanned copies; I can recommend them from personal experience.
Cheers!

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

 

[Archon]

vic wrote:

Hi,

I recently bought an oscilloscope on eBay, and I don't know if the
seller lied in the description or if it was damaged during the
transport, but the trace is completely distorted and shows strange
grid-like patterns. I made a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the
tube ? Could it have been damaged if the oscilloscope received a shock
for example ?

I think the tube is pretty much toast, as well as the scope since there
is no way I could find a replacement tube (Tektronix 2225), but I
wouldn't mind to be proven wrong Thanks.

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

 

[dkelvey@hotmail.com]

On May 8, 1:18 pm, vic <n...@bidouille.org> wrote:

Hi,

I recently bought an oscilloscope on eBay, and I don't know if the
seller lied in the description or if it was damaged during the
transport, but the trace is completely distorted and shows strange
grid-like patterns. I made a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpghttp://img212.imageshack.us/img212/6566/unfocused.jpghttp://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the
tube ? Could it have been damaged if the oscilloscope received a shock
for example ?

I think the tube is pretty much toast, as well as the scope since there
is no way I could find a replacement tube (Tektronix 2225), but I
wouldn't mind to be proven wrong Thanks.

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

 

[vic]

Archon wrote:

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.

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.

 

[vic]

hr(bob) hofmann@att.net wrote:

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.

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.

 

[Archon]

vic wrote:

Archon wrote:
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.

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.
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

 

[Jim Yanik]

vic <news@bidouille.org> wrote in
news:4a0493a2$0$6733$426a74cc@news.free.fr:

Hi,

I recently bought an oscilloscope on eBay, and I don't know if the
seller lied in the description or if it was damaged during the
transport, but the trace is completely distorted and shows strange
grid-like patterns. I made a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the
tube ? Could it have been damaged if the oscilloscope received a shock
for example ?

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

I think the tube is pretty much toast, as well as the scope since there
is no way I could find a replacement tube (Tektronix 2225),

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

but I
wouldn't mind to be proven wrong Thanks.

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

 

[Jim Yanik]

vic <news@bidouille.org> wrote in
news:4a04bf89$0$3099$426a74cc@news.free.fr:

Archon wrote:
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.

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.

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

--
Jim Yanik
jyanik
at
kua.net

 

[hr(bob) hofmann@att.net]

On May 8, 4:08 pm, "Dave M" <masondg4...@comcast.net> wrote:

"vic" <n...@bidouille.org> wrote in message

news:4a0493a2$0$6733$426a74cc@news.free.fr...





Hi,

I recently bought an oscilloscope on eBay, and I don't know if the seller
lied in the description or if it was damaged during the transport, but the
trace is completely distorted and shows strange grid-like patterns. I made
a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the tube
? Could it have been damaged if the oscilloscope received a shock for
example ?

I think the tube is pretty much toast, as well as the scope since there is
no way I could find a replacement tube (Tektronix 2225), but I wouldn't
mind to be proven wrong Thanks.

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
fromhttp://artekmed.startlogic.com/page2.htmlfor $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- Hide quoted text -

- Show quoted text -

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.

 

[PeterD]

On Fri, 08 May 2009 19:34:57 -0400, Archon
<Chipbee40_SpamNo@yahoo.com> wrote:

vic wrote:
Archon wrote:
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.

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.
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

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.

 

[Heinz Schmitz]

Dave M wrote:

You can buy a digital copy
from http://artekmed.startlogic.com/page2.html for $10.00. Artek sells high
quality scanned copies; I can recommend them from personal experience.
Cheers!

They do neither offer a phone number nor their location. And their
Web-Site seems to be broken (with Firefox 2).
http://artekmed.startlogic.com/page6.html

Regards,
H.

 

[Heinz Schmitz]

PeterD wrote:

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.

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

Regards,
H.

 

[Archon]

Heinz Schmitz wrote:

Dave M wrote:

You can buy a digital copy
from http://artekmed.startlogic.com/page2.html for $10.00. Artek sells high
quality scanned copies; I can recommend them from personal experience.
Cheers!

They do neither offer a phone number nor their location. And their
Web-Site seems to be broken (with Firefox 2).
http://artekmed.startlogic.com/page6.html

Regards,
H.



OMFG WTF Here we go again

JC

 

[vic]

Dave M wrote:

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 http://artekmed.startlogic.com/page2.html for $10.00. Artek sells high
quality scanned copies; I can recommend them from personal experience.

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.

 

[Andy Cuffe]

On Mon, 11 May 2009 13:59:37 +0200, Heinz Schmitz
<HeinzSchmitz@gmx.net> wrote:

PeterD wrote:

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.

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

Regards,
H.

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

acuffe@gmail.com

 

[vic]

Archon wrote:

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.

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.

 

[vic]

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.

 

[Dave Platt]

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.

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

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).

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 <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!