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Tektronix 2215A worth repair?
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Geoff
Nov 8, 2011, 6:51:53 PM11/8/11
to
I have a tek 2215A CRO with following fault..
Left side of trace has a ripple, about 1/2 division vert
amplitude and about 25% of horizontal is affected.
Both channels the same
When vert offset is manually swept, the pattern of ripple
changes, still both channels the same
Timebase does not change shape or size of ripple
ripple is 1/2 or 1 cycle but is like someone has put a magnet on
the side of the tube.
Changing attenuator makes no difference.
Was OK a few months ago when last used
If this is a tube fault, I will junk it, what do others think?
Left side of trace has a ripple, about 1/2 division vert
amplitude and about 25% of horizontal is affected.
Both channels the same
When vert offset is manually swept, the pattern of ripple
changes, still both channels the same
Timebase does not change shape or size of ripple
ripple is 1/2 or 1 cycle but is like someone has put a magnet on
the side of the tube.
Changing attenuator makes no difference.
Was OK a few months ago when last used
If this is a tube fault, I will junk it, what do others think?
Archon
Nov 8, 2011, 7:31:16 PM11/8/11
to
been physically dropped/damaged its unlikely the CRT would suddenly
develop a distortion, although your description sounds like a duff tube.
JC
Mark Zacharias
Nov 8, 2011, 9:49:02 PM11/8/11
to
"Geoff" <pub...@email.com> wrote in message
news:Xns9F97CA1...@88.198.244.100...
Always start with the power supply.
Mark Z.
news:Xns9F97CA1...@88.198.244.100...
Mark Z.
Phil Allison
Nov 9, 2011, 12:47:58 AM11/9/11
to
"Geoff"
>
> Left side of trace has a ripple, about 1/2 division vert
> amplitude and about 25% of horizontal is affected.
> Both channels the same
> When vert offset is manually swept, the pattern of ripple
> changes, still both channels the same
> Timebase does not change shape or size of ripple
> ripple is 1/2 or 1 cycle but is like someone has put a magnet on
> the side of the tube.
** Could the case be magnetised in one area ?
> Left side of trace has a ripple, about 1/2 division vert
> amplitude and about 25% of horizontal is affected.
> Both channels the same
> When vert offset is manually swept, the pattern of ripple
> changes, still both channels the same
> Timebase does not change shape or size of ripple
> ripple is 1/2 or 1 cycle but is like someone has put a magnet on
> the side of the tube.
... Phil
N_Cook
Nov 9, 2011, 3:27:06 AM11/9/11
to
Jim Yanik
Nov 9, 2011, 9:48:54 AM11/9/11
to
"Mark Zacharias" <mark_za...@labolgcbs.net> wrote in
news:4eb9ea1f$0$28552$a826...@newsreader.readnews.com:
> "Geoff" <pub...@email.com> wrote in message
> news:Xns9F97CA1...@88.198.244.100...
>>I have a tek 2215A CRO with following fault..
>> Left side of trace has a ripple, about 1/2 division vert
>> amplitude and about 25% of horizontal is affected.
>> Both channels the same
>> When vert offset is manually swept, the pattern of ripple
>> changes, still both channels the same
>> Timebase does not change shape or size of ripple
>> ripple is 1/2 or 1 cycle but is like someone has put a magnet on
>> the side of the tube.
some CRTs had tiny magnets (0.1" dia.) glued on at the factory,for beam
alignment.
one could have come loose.
>> Changing attenuator makes no difference.
>> Was OK a few months ago when last used
>>
>> If this is a tube fault, I will junk it, what do others think?
>
>
> Always start with the power supply.
Yes,PS filter caps,and other decoupling caps on the boards are a problem in
aging scopes.
>
> Mark Z.
>
>
to check tube geometry,input a 6 div high signal with a fast rise time(like
a square wave or time marks),one cycle per division,and turn up intensity
to see the fast rise.
if the tube is bad,you'll see distorted lines.
the distortion remains in the same place as you move trace position
controls.
IMO,2215-series are good scopes,easy to repair.
I have a 2213,one that I built myself from boards discarded by other techs.
Scored a second-grade CRT from the head of CRT mfg,bought the little bits I
needed to finish the scope for about $20.
good analog scopes are hard to find these days.
--
Jim Yanik
jyanik
at
localnet
dot com
news:4eb9ea1f$0$28552$a826...@newsreader.readnews.com:
> "Geoff" <pub...@email.com> wrote in message
> news:Xns9F97CA1...@88.198.244.100...
>>I have a tek 2215A CRO with following fault..
>> Left side of trace has a ripple, about 1/2 division vert
>> amplitude and about 25% of horizontal is affected.
>> Both channels the same
>> When vert offset is manually swept, the pattern of ripple
>> changes, still both channels the same
>> Timebase does not change shape or size of ripple
>> ripple is 1/2 or 1 cycle but is like someone has put a magnet on
>> the side of the tube.
alignment.
one could have come loose.
>> Changing attenuator makes no difference.
>> Was OK a few months ago when last used
>>
>> If this is a tube fault, I will junk it, what do others think?
>
>
> Always start with the power supply.
aging scopes.
>
> Mark Z.
>
>
to check tube geometry,input a 6 div high signal with a fast rise time(like
a square wave or time marks),one cycle per division,and turn up intensity
to see the fast rise.
if the tube is bad,you'll see distorted lines.
the distortion remains in the same place as you move trace position
controls.
IMO,2215-series are good scopes,easy to repair.
I have a 2213,one that I built myself from boards discarded by other techs.
Scored a second-grade CRT from the head of CRT mfg,bought the little bits I
needed to finish the scope for about $20.
good analog scopes are hard to find these days.
--
Jim Yanik
jyanik
at
localnet
dot com
Geo
Nov 9, 2011, 12:55:30 PM11/9/11
to
On Tue, 8 Nov 2011 23:51:53 +0000 (UTC), Geoff <pub...@email.com>
wrote:
>I have a tek 2215A CRO with following fault..
>Left side of trace has a ripple, about 1/2 division vert
>amplitude and about 25% of horizontal is affected.
>Both channels the same
>When vert offset is manually swept, the pattern of ripple
>changes, still both channels the same
I don't know this scope but used to work on another manufacturer's
models.
On one in particular, you could sometimes see this fault - it got
worse as the y shift was changed. As I recall, the problem was
timebase ripple (after flyback) on the supply to one of the tube
accelerating electrodes. The effect was more noticable as the beam was
moved (y shift) nearer to the electrode. You would need a second
scope to probe the tube pins to confirm this.
wrote:
>I have a tek 2215A CRO with following fault..
>Left side of trace has a ripple, about 1/2 division vert
>amplitude and about 25% of horizontal is affected.
>Both channels the same
>When vert offset is manually swept, the pattern of ripple
>changes, still both channels the same
models.
On one in particular, you could sometimes see this fault - it got
worse as the y shift was changed. As I recall, the problem was
timebase ripple (after flyback) on the supply to one of the tube
accelerating electrodes. The effect was more noticable as the beam was
moved (y shift) nearer to the electrode. You would need a second
scope to probe the tube pins to confirm this.
Geoff
Nov 9, 2011, 7:42:04 PM11/9/11
to
"Phil Allison" <phi...@tpg.com.au> wrote in
news:9huign...@mid.individual.net:
I took the case off and no difference, your implied suggestion
that a change in magnetic field caused this matches what I
observe, ie no electronic settings change the waveform, it looks
like when someone shoves a magnet near a crt. I have not removed
the tube screen but I have shaken it and nothing like a magnet
bouncing around can be heard, I may just give up now, it is not
a paying job just an old CRO we use occasionally for R&D work,
we have newer better ones around including tek analog CRO's.
news:9huign...@mid.individual.net:
that a change in magnetic field caused this matches what I
observe, ie no electronic settings change the waveform, it looks
like when someone shoves a magnet near a crt. I have not removed
the tube screen but I have shaken it and nothing like a magnet
bouncing around can be heard, I may just give up now, it is not
a paying job just an old CRO we use occasionally for R&D work,
we have newer better ones around including tek analog CRO's.
Phil Allison
Nov 10, 2011, 2:31:00 AM11/10/11
to
"Geoff"
> I took the case off and no difference, your implied suggestion
> that a change in magnetic field caused this matches what I
> observe, ie no electronic settings change the waveform, it looks
> like when someone shoves a magnet near a crt. I have not removed
> the tube screen but I have shaken it and nothing like a magnet
> bouncing around can be heard,
There must be a chance the steel mesh has become magnetised.
Suggest you play around with a small magnet near the tube face and see what
happens.
FYI:
There is a fine steel mesh just behind the face of the tube that has final
acceleration voltage applied to it - if you de-focus the beam you can
usually see the pattern of the mesh projected onto the phosphor.
... Phil
hrho...@att.net
Nov 10, 2011, 10:21:57 AM11/10/11
to
Geoff
Nov 13, 2011, 8:13:45 PM11/13/11
to
"Phil Allison" <phi...@tpg.com.au> wrote in
news:9i1ctv...@mid.individual.net:
I have played around with a magnet, can get trace to wobble
around as expected but it comes back to the same position once
magnet removed. This is true for the unshielded part behind
screen and the conical tube shield. I will try a degausser
once I find or make one
http://i251.photobucket.com/albums/gg302/triode101/focus_limit
_ccw1.jpg
http://i251.photobucket.com/albums/gg302/triode101/focus_limit
_cw1.jpg
http://i251.photobucket.com/albums/gg302/triode101/focus_limit
_ccw2.jpg
http://i251.photobucket.com/albums/gg302/triode101/2215a.jpg
http://i251.photobucket.com/albums/gg302/triode101/2215b.jpg
Archon
Nov 14, 2011, 7:46:18 AM11/14/11
to
On 11/13/2011 8:13 PM, Geoff wrote:
>
> Links below for pics taken with webcam. Mesh is visible.
> I have played around with a magnet, can get trace to wobble
> around as expected but it comes back to the same position once
> magnet removed. This is true for the unshielded part behind
> screen and the conical tube shield. I will try a degausser
> once I find or make one
>
> http://i251.photobucket.com/albums/gg302/triode101/focus_limit
> _ccw1.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/focus_limit
> _cw1.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/focus_limit
> _ccw2.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/2215a.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/2215b.jpg
If the distortion stays constant with the traces as they move up the
>
> Links below for pics taken with webcam. Mesh is visible.
> I have played around with a magnet, can get trace to wobble
> around as expected but it comes back to the same position once
> magnet removed. This is true for the unshielded part behind
> screen and the conical tube shield. I will try a degausser
> once I find or make one
>
> http://i251.photobucket.com/albums/gg302/triode101/focus_limit
> _ccw1.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/focus_limit
> _cw1.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/focus_limit
> _ccw2.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/2215a.jpg
>
> http://i251.photobucket.com/albums/gg302/triode101/2215b.jpg
screen its not the CRT
If the distortion is fixed in that area of the CRT then the CRT is
internally damaged.
Magnets and deguassers will not cure this.
IMO its a broken CRT
JC
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