Topics

2235 Bad CRT


Peter Florance
 

Hello
New to the list
Purchased a TEK 2235M with low hours on it and it has a strange problem.
With input grounded, moving trace up and down, either trace distorts. When
trace is at the top, the left 1/2" is distorted upwards. When at the bottom
there is a 1/2" area near the right side of the CRT is distorted downwards.
Like the CRT is magnetized or something. Near the middle, the line is
pretty straight. Looking at verticle deflection plates with another scope I
don't see any AC signal at all. Like it's coming from inside the tube.
Trace is bright and sharp other than bends in it
Bad CRT?
Nothing magnetic stuck to shield or anywhere else that I could find.

Thanks for your help!

Peter Florance
audserv@...


John Miles <jmiles@...>
 

It was probably dropped. I assume a sine-wave display looks like the 485 I
sold on ebay awhile back: http://209.95.122.40/jm/485bad.html ... if so,
that's the problem. Nothing you can do about it, unfortunately.

-- jm

-----Original Message-----
From: Peter Florance [SMTP:audserv@...]
Sent: Wednesday, July 11, 2001 11:55 AM
To: 'TekScopes@...'
Subject: [TekScopes] 2235 Bad CRT

Hello
New to the list
Purchased a TEK 2235M with low hours on it and it has a strange problem.
With input grounded, moving trace up and down, either trace distorts. When
trace is at the top, the left 1/2" is distorted upwards. When at the bottom

there is a 1/2" area near the right side of the CRT is distorted downwards.

Like the CRT is magnetized or something. Near the middle, the line is
pretty straight. Looking at verticle deflection plates with another scope I

don't see any AC signal at all. Like it's coming from inside the tube.
Trace is bright and sharp other than bends in it
Bad CRT?
Nothing magnetic stuck to shield or anywhere else that I could find.

Thanks for your help!

Peter Florance
audserv@...


Ashton Brown <ashtonb@...>
 

Hmmm - dropped you say? Mu metal shield around CRT. It was annealed at
birth. Dunno chracteristics of Tek's exact choices but do recall: these
shields cannot stand a large blow to metal. Just possibly - a new
shield would be enough, from a parts-hog. Or try running CRT out of
shield (yes a PITA to set up). As to reannealing - have long since
forgotten temp you might have to get it up to and.. the drill for
cooling - all rather critical IIRC)

Good luck!

Ashton

John Miles wrote:


It was probably dropped. I assume a sine-wave display looks like the 485 I
sold on ebay awhile back: http://209.95.122.40/jm/485bad.html ... if so,
that's the problem. Nothing you can do about it, unfortunately.

-- jm

-----Original Message-----
From: Peter Florance [SMTP:audserv@...]
Sent: Wednesday, July 11, 2001 11:55 AM
To: 'TekScopes@...'
Subject: [TekScopes] 2235 Bad CRT

Hello
New to the list
Purchased a TEK 2235M with low hours on it and it has a strange problem.
With input grounded, moving trace up and down, either trace distorts. When
trace is at the top, the left 1/2" is distorted upwards. When at the bottom

there is a 1/2" area near the right side of the CRT is distorted downwards.

Like the CRT is magnetized or something. Near the middle, the line is
pretty straight. Looking at verticle deflection plates with another scope I

don't see any AC signal at all. Like it's coming from inside the tube.
Trace is bright and sharp other than bends in it
Bad CRT?
Nothing magnetic stuck to shield or anywhere else that I could find.

Thanks for your help!

Peter Florance
audserv@...

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



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Peter Florance
 

Thanks for the replies.
Other than that, scope is in perfect cosmetic condition. Guessing
switches should be a little noisy from dis-use, but don't appear to
be.
Shield on this unit is pretty simple looking - just a dunce cap with
cut-outs for deflection plat pins. I have some mu metal but am no tin-
banger. BTW, there are one or two black specs on the INSIDE of the
glass.
Paid 400.00 locally for the scope which was with probes book and
cords. Worth trying locate used tube?

Thanks again
Peter




--- In TekScopes@y..., Ashton Brown <ashtonb@j...> wrote:
Hmmm - dropped you say? Mu metal shield around CRT. It was
annealed at
birth. Dunno chracteristics of Tek's exact choices but do recall:
these
shields cannot stand a large blow to metal. Just possibly - a new
shield would be enough, from a parts-hog. Or try running CRT out of
shield (yes a PITA to set up). As to reannealing - have long since
forgotten temp you might have to get it up to and.. the drill for
cooling - all rather critical IIRC)

Good luck!

Ashton

John Miles wrote:

It was probably dropped. I assume a sine-wave display looks like
the 485 I
sold on ebay awhile back: http://209.95.122.40/jm/485bad.html ...
if so,
that's the problem. Nothing you can do about it, unfortunately.

-- jm

-----Original Message-----
From: Peter Florance [SMTP:audserv@e...]
Sent: Wednesday, July 11, 2001 11:55 AM
To: 'TekScopes@y...'
Subject: [TekScopes] 2235 Bad CRT

Hello
New to the list
Purchased a TEK 2235M with low hours on it and it has a strange
problem.
With input grounded, moving trace up and down, either trace
distorts. When
trace is at the top, the left 1/2" is distorted upwards. When at
the bottom

there is a 1/2" area near the right side of the CRT is distorted
downwards.

Like the CRT is magnetized or something. Near the middle, the
line is
pretty straight. Looking at verticle deflection plates with
another scope I

don't see any AC signal at all. Like it's coming from inside the
tube.
Trace is bright and sharp other than bends in it
Bad CRT?
Nothing magnetic stuck to shield or anywhere else that I could
find.

Thanks for your help!

Peter Florance
audserv@e...

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/


Miroslav Pokorni <mpokorni@...>
 

I do not claim to know it as a fact, but it seems to me that a blow that
would upset crystal lattice of Mu metal, i.e. wreck annealing, would break a
lot of other components, too. Having a magnet do that is more plausible.

Regards

Miroslav Pokorni

-----Original Message-----
From: Ashton Brown [mailto:ashtonb@...]
Sent: Wednesday, July 11, 2001 7:05 PM
To: TekScopes@...
Subject: Re: [TekScopes] 2235 Bad CRT

Hmmm - dropped you say? Mu metal shield around CRT. It was
annealed at
birth. Dunno chracteristics of Tek's exact choices but do
recall: these
shields cannot stand a large blow to metal. Just possibly -
a new
shield would be enough, from a parts-hog. Or try running
CRT out of
shield (yes a PITA to set up). As to reannealing - have
long since
forgotten temp you might have to get it up to and.. the
drill for
cooling - all rather critical IIRC)

Good luck!

Ashton

John Miles wrote:
>
> It was probably dropped. I assume a sine-wave display
looks like the 485 I
> sold on ebay awhile back:
http://209.95.122.40/jm/485bad.html ... if so,
> that's the problem. Nothing you can do about it,
unfortunately.
>
> -- jm
>
> -----Original Message-----
> From: Peter Florance [SMTP:audserv@...]
> Sent: Wednesday, July 11, 2001 11:55 AM
> To: 'TekScopes@...'
> Subject: [TekScopes] 2235 Bad CRT
>
> Hello
> New to the list
> Purchased a TEK 2235M with low hours on it and it has a
strange problem.
> With input grounded, moving trace up and down, either
trace distorts. When
> trace is at the top, the left 1/2" is distorted upwards.
When at the bottom
>
> there is a 1/2" area near the right side of the CRT is
distorted downwards.
>
> Like the CRT is magnetized or something. Near the middle,
the line is
> pretty straight. Looking at verticle deflection plates
with another scope I
>
> don't see any AC signal at all. Like it's coming from
inside the tube.
> Trace is bright and sharp other than bends in it
> Bad CRT?
> Nothing magnetic stuck to shield or anywhere else that I
could find.
>
> Thanks for your help!
>
> Peter Florance
> audserv@...
>
> To unsubscribe from this group, send an email to:
> TekScopes-unsubscribe@...
>
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to
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Ashton Brown <ashtonb@...>
 

I'm not at all sure how many ergs you have to transmit locally; I recall
that we deemed the smaller ones - used around photomultiplier tubes - to
be "rather fragile" = not to be dropped on floor even.. Agreed re
"whole scope" ~number of G's likely to transmit that much force to the
shield, qithout probably cracking boards etc. (But I've seen some
dropped scopes, visibly mangled - still work! Tek heap good G-tester
folk.)

Now something falling on shield, with scope open? And especially a
local hit - like a rod, say? Needn't necessarily produce a visible mark
in the paint. So.. not enough info for more than a guesstimate. Still
- if you hunt up a CRT and that wasn't it?

Just a thought.

Ashton

Miroslav Pokorni wrote:


I do not claim to know it as a fact, but it seems to me that a blow that
would upset crystal lattice of Mu metal, i.e. wreck annealing, would break a
lot of other components, too. Having a magnet do that is more plausible.

Regards

Miroslav Pokorni

-----Original Message-----
From: Ashton Brown [mailto:ashtonb@...]
Sent: Wednesday, July 11, 2001 7:05 PM
To: TekScopes@...
Subject: Re: [TekScopes] 2235 Bad CRT

Hmmm - dropped you say? Mu metal shield around CRT. It was
annealed at
birth. Dunno chracteristics of Tek's exact choices but do
recall: these
shields cannot stand a large blow to metal. Just possibly -
a new
shield would be enough, from a parts-hog. Or try running
CRT out of
shield (yes a PITA to set up). As to reannealing - have
long since
forgotten temp you might have to get it up to and.. the
drill for
cooling - all rather critical IIRC)

Good luck!

Ashton

John Miles wrote:
>
> It was probably dropped. I assume a sine-wave display
looks like the 485 I
> sold on ebay awhile back:
http://209.95.122.40/jm/485bad.html ... if so,
> that's the problem. Nothing you can do about it,
unfortunately.
>
> -- jm
>
> -----Original Message-----
> From: Peter Florance [SMTP:audserv@...]
> Sent: Wednesday, July 11, 2001 11:55 AM
> To: 'TekScopes@...'
> Subject: [TekScopes] 2235 Bad CRT
>
> Hello
> New to the list
> Purchased a TEK 2235M with low hours on it and it has a
strange problem.
> With input grounded, moving trace up and down, either
trace distorts. When
> trace is at the top, the left 1/2" is distorted upwards.
When at the bottom
>
> there is a 1/2" area near the right side of the CRT is
distorted downwards.
>
> Like the CRT is magnetized or something. Near the middle,
the line is
> pretty straight. Looking at verticle deflection plates
with another scope I
>
> don't see any AC signal at all. Like it's coming from
inside the tube.
> Trace is bright and sharp other than bends in it
> Bad CRT?
> Nothing magnetic stuck to shield or anywhere else that I
could find.
>
> Thanks for your help!
>
> Peter Florance
> audserv@...
>
> To unsubscribe from this group, send an email to:
> TekScopes-unsubscribe@...
>
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/


To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


John Miles <jmiles@...>
 

The key point is that damage to the mu-metal shield will NOT cause a
magnetic anomaly to appear on the screen -- it will only impair the shield's
ability to keep external fields out. If your visual glitch doesn't change
shape with the horizontal timebase, it can't be caused by an external AC
field (e.g., 60 Hz from the power transformer). It can only be caused by a
DC magnetic source, of which there aren't any in an oscilloscope, or by a
deformed deflection structure internal to the CRT.

The black spots in your CRT phosphor are caused by solid objects rattling
around inside the tube scraping the coating off the screen. If you turn the
scope upside down and shake it, it'll probably look like someone went crazy
with an Etch-A-Sketch.

Your CRT is damaged; it's not the shield or anything else. If I were you
I'd be looking for at least a partial rebate on the sales price on this one.

-- jm

----- Original Message -----
From: "Ashton Brown" <ashtonb@...>
To: <TekScopes@...>
Sent: Thursday, July 12, 2001 12:53 PM
Subject: Re: [TekScopes] 2235 Bad CRT


I'm not at all sure how many ergs you have to transmit locally; I recall
that we deemed the smaller ones - used around photomultiplier tubes - to
be "rather fragile" = not to be dropped on floor even.. Agreed re
"whole scope" ~number of G's likely to transmit that much force to the
shield, qithout probably cracking boards etc. (But I've seen some
dropped scopes, visibly mangled - still work! Tek heap good G-tester
folk.)

Now something falling on shield, with scope open? And especially a
local hit - like a rod, say? Needn't necessarily produce a visible mark
in the paint. So.. not enough info for more than a guesstimate. Still
- if you hunt up a CRT and that wasn't it?

Just a thought.

Ashton

Miroslav Pokorni wrote:

I do not claim to know it as a fact, but it seems to me that a blow that
would upset crystal lattice of Mu metal, i.e. wreck annealing, would
break a
lot of other components, too. Having a magnet do that is more plausible.

Regards

Miroslav Pokorni

-----Original Message-----
From: Ashton Brown [mailto:ashtonb@...]
Sent: Wednesday, July 11, 2001 7:05 PM
To: TekScopes@...
Subject: Re: [TekScopes] 2235 Bad CRT

Hmmm - dropped you say? Mu metal shield around CRT. It
was
annealed at
birth. Dunno chracteristics of Tek's exact choices but
do
recall: these
shields cannot stand a large blow to metal. Just
possibly -
a new
shield would be enough, from a parts-hog. Or try
running
CRT out of
shield (yes a PITA to set up). As to reannealing - have
long since
forgotten temp you might have to get it up to and.. the
drill for
cooling - all rather critical IIRC)

Good luck!

Ashton

John Miles wrote:
>
> It was probably dropped. I assume a sine-wave display
looks like the 485 I
> sold on ebay awhile back:
http://209.95.122.40/jm/485bad.html ... if so,
> that's the problem. Nothing you can do about it,
unfortunately.
>
> -- jm
>
> -----Original Message-----
> From: Peter Florance [SMTP:audserv@...]
> Sent: Wednesday, July 11, 2001 11:55 AM
> To: 'TekScopes@...'
> Subject: [TekScopes] 2235 Bad CRT
>
> Hello
> New to the list
> Purchased a TEK 2235M with low hours on it and it has
a
strange problem.
> With input grounded, moving trace up and down, either
trace distorts. When
> trace is at the top, the left 1/2" is distorted
upwards.
When at the bottom
>
> there is a 1/2" area near the right side of the CRT is
distorted downwards.
>
> Like the CRT is magnetized or something. Near the
middle,
the line is
> pretty straight. Looking at verticle deflection plates
with another scope I
>
> don't see any AC signal at all. Like it's coming from
inside the tube.
> Trace is bright and sharp other than bends in it
> Bad CRT?
> Nothing magnetic stuck to shield or anywhere else that
I
could find.
>
> Thanks for your help!
>
> Peter Florance
> audserv@...
>
> To unsubscribe from this group, send an email to:
> TekScopes-unsubscribe@...
>
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/


To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/



Ashton Brown <ashtonb@...>
 

John Miles wrote:

The key point is that damage to the mu-metal shield will NOT cause a
magnetic anomaly to appear on the screen -- it will only impair the shield's
ability to keep external fields out. If your visual glitch doesn't change
shape with the horizontal timebase, it can't be caused by an external AC
field (e.g., 60 Hz from the power transformer). It can only be caused by a
DC magnetic source, of which there aren't any in an oscilloscope, or by a
deformed deflection structure internal to the CRT.

The black spots in your CRT phosphor are caused by solid objects rattling
around inside the tube scraping the coating off the screen. If you turn the
scope upside down and shake it, it'll probably look like someone went crazy
with an Etch-A-Sketch.

Your CRT is damaged; it's not the shield or anything else. If I were you
I'd be looking for at least a partial rebate on the sales price on this one.

-- jm
Ah.. RTP indeed. Apologies for red herring. In rush reading, and
remembering the wrong detail - indeed such a localized 'spot' unchanged
by timebase setting Isn't bloody likely to be other than a malformed or
otherwise screwy internal piece. Or a bizarre local effect more ikely
to be found in a superconducting lab :[

As EmilY Litella said, "never mind!" :-) (I miss Gilda Radner)

Ashton


Peter Florance
 

Looking at your auction link then trying the same on this scope with
sine wave gave me the answer. the 2 scopes are wounded cousins....

Seller is trying to find a tube. I'd like to keep it as it's really
clean but seems than only this one and 2236 used this tube 154-0861-
00.
BTW he has a lot of old Tek parts to sell (probably dirt cheap as a
lot) as his health is not good anymore so he's forced to get out of
the business. I've bought from him over the years and he's always
stood behind his sales.
Thanks again for all the help and if anyone has tube or junker
2235/2236 I'm interested.

Cheers
Peter Florance


--- In TekScopes@y..., "John Miles" <jmiles@p...> wrote:
The key point is that damage to the mu-metal shield will NOT cause a
magnetic anomaly to appear on the screen -- it will only impair the
shield's
ability to keep external fields out. If your visual glitch doesn't
change
shape with the horizontal timebase, it can't be caused by an
external AC
field (e.g., 60 Hz from the power transformer). It can only be
caused by a
DC magnetic source, of which there aren't any in an oscilloscope,
or by a
deformed deflection structure internal to the CRT.

The black spots in your CRT phosphor are caused by solid objects
rattling
around inside the tube scraping the coating off the screen. If you
turn the
scope upside down and shake it, it'll probably look like someone
went crazy
with an Etch-A-Sketch.

Your CRT is damaged; it's not the shield or anything else. If I
were you
I'd be looking for at least a partial rebate on the sales price on
this one.

-- jm


John Miles <jmiles@...>
 

It's a bit of a long shot, but try Tucker Electronics
(http://www.tucker.com). They occasionally sell replacement CRTs for Tek
and HP instruments.

-- jm

-----Original Message-----
From: audserv@... [SMTP:audserv@...]
Sent: Thursday, July 12, 2001 3:19 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2235 Bad CRT

Looking at your auction link then trying the same on this scope with
sine wave gave me the answer. the 2 scopes are wounded cousins....

Seller is trying to find a tube. I'd like to keep it as it's really
clean but seems than only this one and 2236 used this tube 154-0861-
00.
BTW he has a lot of old Tek parts to sell (probably dirt cheap as a
lot) as his health is not good anymore so he's forced to get out of
the business. I've bought from him over the years and he's always
stood behind his sales.
Thanks again for all the help and if anyone has tube or junker
2235/2236 I'm interested.

Cheers
Peter Florance


Miroslav Pokorni <mpokorni@...>
 

If it is CRT that you are looking for, following web site lists few:

http://www.reprise.com/host/tektronix/resources/crt_sources.asp
<http://www.reprise.com/host/tektronix/resources/crt_sources.asp>

Regards

Miroslav Pokorni

-----Original Message-----
From: John Miles [mailto:jmiles@...]
Sent: Thursday, July 12, 2001 3:46 PM
To: 'TekScopes@...'
Subject: RE: [TekScopes] Re: 2235 Bad CRT

It's a bit of a long shot, but try Tucker Electronics
(http://www.tucker.com). They occasionally sell replacement
CRTs for Tek
and HP instruments.

-- jm

-----Original Message-----
From: audserv@... [SMTP:audserv@...]
Sent: Thursday, July 12, 2001 3:19 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2235 Bad CRT

Looking at your auction link then trying the same on this
scope with
sine wave gave me the answer. the 2 scopes are wounded
cousins....

Seller is trying to find a tube. I'd like to keep it as it's
really
clean but seems than only this one and 2236 used this tube
154-0861-
00.
BTW he has a lot of old Tek parts to sell (probably dirt
cheap as a
lot) as his health is not good anymore so he's forced to get
out of
the business. I've bought from him over the years and he's
always
stood behind his sales.
Thanks again for all the help and if anyone has tube or
junker
2235/2236 I'm interested.

Cheers
Peter Florance



To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/


james89es@...
 

BTW he has a lot of old Tek parts to sell (probably dirt cheap as a
lot) as his health is not good anymore so he's forced to get out of
the business. I've bought from him over the years and he's always
stood behind his sales.
I may be looking for parts, is there a link or email for this seller?

Jim


Peter Florance
 

I you (or anyone else interested) will email me privately, I'll reply
with his phone number. He's internet challenged....

Thanks
Peter Florance audserv@...



--- In TekScopes@y..., james89es@y... wrote:

BTW he has a lot of old Tek parts to sell (probably dirt cheap as
a
lot) as his health is not good anymore so he's forced to get out
of
the business. I've bought from him over the years and he's always
stood behind his sales.
I may be looking for parts, is there a link or email for this
seller?

Jim


candmmiles6102@...
 

Who is the "he" referred to here,.... have an e-mail address?

Thanks.

Chuck