Triggering proglems with Tek465

S

Sam Goldwasser

Guest
This is the original 465, not the B version.

Time base does not run in any mode including AUTO and LINE. I have
seen very sporatic triggering before it warmed up when some selections
were changed like slop +/- or sweep speed.

Problem appeared after being in non-climate controlled storage so
could just mean reseating of internal connectors, etc.

Any comments appreciated before I open it up.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
Jim Yanik <jyanik@abuse.gov> writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6whdvbq5w2.fsf@saul.cis.upenn.edu:

This is the original 465, not the B version.

Time base does not run in any mode including AUTO and LINE. I have
seen very sporatic triggering before it warmed up when some selections
were changed like slop +/- or sweep speed.

Problem appeared after being in non-climate controlled storage so
could just mean reseating of internal connectors, etc.

Any comments appreciated before I open it up.

Well,if you are not getting any sweep in auto mode,then the problem is in
the sweep circuit or holdoff,not triggering.It could be a failing sweep
control logic IC,that big 155 prefix IC.Or it could be 151-0220-xx
transistor,they caused wierd problems.Swap some from another circuit,maybe
B sweep gen,see if that makes a difference.
Start by determining where the sweep is;waiting to ramp(waiting for
trigger),ramped fully(down,IIRC),or in holdoff.
Click to expand...
I believe the beam is sitting on the right side of the screen.

This failure is in all sweep speeds,of course?
Click to expand...
Yes, would appear to be all though now that you ask, I'll check every one.

I guess the next thing to do is to just make sure everything is seated
and contacts are clean.

BTW, on my 465B that I asked about a few months ago, recall there were
two problems: X-Y mode didn't work and there was a high frequency ripple
on both traces, about 1/2 of a small division. Well, the X-Y problem
turned out to be one of those gold coaxes that got pulled out of its
socket when the case was installed. The ripple is still a mystery
as probing the power rails shows nothing. It's in the main vertical
PCB (sorry, don't recall the official Tek name!), not the output as
removing the delay line eliminates the ripple.

Thanks.

--- sam
 
Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6whdvbq5w2.fsf@saul.cis.upenn.edu:

This is the original 465, not the B version.

Time base does not run in any mode including AUTO and LINE. I have
seen very sporatic triggering before it warmed up when some selections
were changed like slop +/- or sweep speed.

Problem appeared after being in non-climate controlled storage so
could just mean reseating of internal connectors, etc.

Any comments appreciated before I open it up.
Click to expand...


Well,if you are not getting any sweep in auto mode,then the problem is in
the sweep circuit or holdoff,not triggering.It could be a failing sweep
control logic IC,that big 155 prefix IC.Or it could be 151-0220-xx
transistor,they caused wierd problems.Swap some from another circuit,maybe
B sweep gen,see if that makes a difference.
Start by determining where the sweep is;waiting to ramp(waiting for
trigger),ramped fully(down,IIRC),or in holdoff.

This failure is in all sweep speeds,of course?

--
Jim Yanik
jyanik-at-kua.net
 
Jim Yanik <jyanik@abuse.gov> writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
I believe the beam is sitting on the right side of the screen.

Then the sweep has ramped(down?),and is not being reset,problem in the end-
of-sweep circuit.(EOS comparator?) The circuit description will help here
in identifying the parts that do this job.

Normal operation;
1.spot on left,sweep waiting for trigger
2.trigger begins sweep ramping,spot moves across screen
3.spot on right,sweep rampled fully,EOS returns ramp to 'zero',spot 'flys
back' or retraces to left of screen.
4.sweep in holdoff,locking out triggers
5.holdoff ends,waiting for next trigger

BTW, on my 465B that I asked about a few months ago, recall there were
two problems: X-Y mode didn't work and there was a high frequency
ripple on both traces, about 1/2 of a small division. Well, the X-Y
problem turned out to be one of those gold coaxes that got pulled out
of its socket when the case was installed.

They're called a Peltola connector.

The ripple is still a
mystery as probing the power rails shows nothing. It's in the main
vertical PCB

vertical preamp? Or vertical output amp.
Click to expand...
Well, the large PCB on the left side. :) Unplugging the delay line
eliminates the ripple.

You probably are getting a HF oscillation somewhere;those can be hard to
TS.Perhaps a loose screw? Or one (or more)of the HF trim caps could be
misadjusted.Even a missing ferrite bead that sometimes were placed on a
xstr's lead.
Click to expand...
Hmmm. OK, a challenge for a rainy day.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6woepj30p7.fsf@saul.cis.upenn.edu:

Jim Yanik <jyanik@abuse.gov> writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6whdvbq5w2.fsf@saul.cis.upenn.edu:

This is the original 465, not the B version.

Time base does not run in any mode including AUTO and LINE. I have
seen very sporatic triggering before it warmed up when some
selections were changed like slop +/- or sweep speed.

Problem appeared after being in non-climate controlled storage so
could just mean reseating of internal connectors, etc.

Any comments appreciated before I open it up.

Well,if you are not getting any sweep in auto mode,then the problem
is in the sweep circuit or holdoff,not triggering.It could be a
failing sweep control logic IC,that big 155 prefix IC.Or it could be
151-0220-xx transistor,they caused wierd problems.Swap some from
another circuit,maybe B sweep gen,see if that makes a difference.
Start by determining where the sweep is;waiting to ramp(waiting for
trigger),ramped fully(down,IIRC),or in holdoff.

I believe the beam is sitting on the right side of the screen.
Click to expand...
Then the sweep has ramped(down?),and is not being reset,problem in the end-
of-sweep circuit.(EOS comparator?) The circuit description will help here
in identifying the parts that do this job.


Normal operation;
1.spot on left,sweep waiting for trigger
2.trigger begins sweep ramping,spot moves across screen
3.spot on right,sweep rampled fully,EOS returns ramp to 'zero',spot 'flys
back' or retraces to left of screen.
4.sweep in holdoff,locking out triggers
5.holdoff ends,waiting for next trigger


This failure is in all sweep speeds,of course?

Yes, would appear to be all though now that you ask, I'll check every
one.

I guess the next thing to do is to just make sure everything is seated
and contacts are clean.

BTW, on my 465B that I asked about a few months ago, recall there were
two problems: X-Y mode didn't work and there was a high frequency
ripple on both traces, about 1/2 of a small division. Well, the X-Y
problem turned out to be one of those gold coaxes that got pulled out
of its socket when the case was installed.
Click to expand...
They're called a Peltola connector.

The ripple is still a
mystery as probing the power rails shows nothing. It's in the main
vertical PCB
Click to expand...
vertical preamp? Or vertical output amp.

(sorry, don't recall the official Tek name!), not the
output as removing the delay line eliminates the ripple.

Thanks.

--- sam
Click to expand...
You probably are getting a HF oscillation somewhere;those can be hard to
TS.Perhaps a loose screw? Or one (or more)of the HF trim caps could be
misadjusted.Even a missing ferrite bead that sometimes were placed on a
xstr's lead.

--
Jim Yanik
jyanik-at-kua.net
 
Sam Goldwasser wrote:
Well, the large PCB on the left side. :) Unplugging the delay line
eliminates the ripple.

You probably are getting a HF oscillation somewhere;those can be hard to
TS.Perhaps a loose screw? Or one (or more)of the HF trim caps could be
misadjusted.Even a missing ferrite bead that sometimes were placed on a
xstr's lead.

Hmmm. OK, a challenge for a rainy day.
Click to expand...
Please let us know if you find it. (My 465B also has a tiny bit of HF
ripple, unnoticeable unless you really look for it.)

--
John Miller
Email address: domain, n4vu.com; username, jsm

Next, upon a stool, we've a sight to make you drool.
Seven virgins and a mule, keep it cool, keep it cool.
-ELP, "Karn Evil 9" (1st Impression, Part 2)
 
John Miller <me@privacy.net> writes:

Sam Goldwasser wrote:
Well, the large PCB on the left side. :) Unplugging the delay line
eliminates the ripple.

You probably are getting a HF oscillation somewhere;those can be hard to
TS.Perhaps a loose screw? Or one (or more)of the HF trim caps could be
misadjusted.Even a missing ferrite bead that sometimes were placed on a
xstr's lead.

Hmmm. OK, a challenge for a rainy day.

Please let us know if you find it. (My 465B also has a tiny bit of HF
ripple, unnoticeable unless you really look for it.)
Click to expand...
Yeah, this is the same. It's always present (even with the input set to
GND) but only really visible and annoying on certain sweep speeds where
it happens to sort of sync. And, interestingly, also more visible in X-Y mode.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
Jim Yanik <jyanik@abuse.gov> writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6woepj30p7.fsf@saul.cis.upenn.edu:

Jim Yanik <jyanik@abuse.gov> writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6whdvbq5w2.fsf@saul.cis.upenn.edu:

This is the original 465, not the B version.

Time base does not run in any mode including AUTO and LINE. I have
seen very sporatic triggering before it warmed up when some
selections were changed like slop +/- or sweep speed.

Problem appeared after being in non-climate controlled storage so
could just mean reseating of internal connectors, etc.

Any comments appreciated before I open it up.

Well,if you are not getting any sweep in auto mode,then the problem
is in the sweep circuit or holdoff,not triggering.It could be a
failing sweep control logic IC,that big 155 prefix IC.Or it could be
151-0220-xx transistor,they caused wierd problems.Swap some from
another circuit,maybe B sweep gen,see if that makes a difference.
Start by determining where the sweep is;waiting to ramp(waiting for
trigger),ramped fully(down,IIRC),or in holdoff.

I believe the beam is sitting on the right side of the screen.

Then the sweep has ramped(down?),and is not being reset,problem in the end-
of-sweep circuit.(EOS comparator?) The circuit description will help here
in identifying the parts that do this job.


Normal operation;
1.spot on left,sweep waiting for trigger
2.trigger begins sweep ramping,spot moves across screen
3.spot on right,sweep rampled fully,EOS returns ramp to 'zero',spot 'flys
back' or retraces to left of screen.
4.sweep in holdoff,locking out triggers
5.holdoff ends,waiting for next trigger
Click to expand...
Some more info:

1. The spot is at the right side of the screen except in X-Y mode, which
works correctly.

2. Switching from X-Y to any sweep speed when in AUTO will result in a
single sweep from left to right.

3. Switching from X-Y to any sweep speed when in NORM or SINGLE results in the
spot remaining on the left side of the screen, except perhaps if HOLDOFF
or TRIG SLOPE is changed. Triggering doesn't appear to have any
effect.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
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