Minor problems with Tek465B

S

Sam Goldwasser

Guest
I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces independent
of vertical amplifier gain settings. It's about 1/2 mm in height.

2. There is no response to X in X-Y mode. The beam is stuck at the left
edge of the screen. The channel 1 controls have no effect and the
horizontal position only has a minor effect noticeable when pushing the
beam finder button.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6wfzhg6lvs.fsf@saul.cis.upenn.edu:

I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces
independent
of vertical amplifier gain settings. It's about 1/2 mm in height.
Click to expand...
Could be a HF cap adjustment gone bad;those tiny ceramic trimmer caps
developed a 'black oxide' on the underside,insulating the rotor from the
solder tab.Or the HF cal is off,or the ground on the delay line is not
making a good ground connection,maybe a loose ground screw on a PCB.

2. There is no response to X in X-Y mode. The beam is stuck at the
left
edge of the screen. The channel 1 controls have no effect and the
horizontal position only has a minor effect noticeable when pushing
the beam finder button.

Thanks.
Click to expand...
Perhaps a coax Peltola center pin was bent over instead of it's proper
insertion in the PCB receptacle.I cannot recall if the time/div knob has to
also be in X-Y mode for this function to work on this model.If so,could be
a broken LF cam switch contact(small phosphor-bronze switch contact under
the time/div cam drum)

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

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6wfzhg6lvs.fsf@saul.cis.upenn.edu:

I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces
independent
of vertical amplifier gain settings. It's about 1/2 mm in height.

Could be a HF cap adjustment gone bad;those tiny ceramic trimmer caps
developed a 'black oxide' on the underside,insulating the rotor from the
solder tab.Or the HF cal is off,or the ground on the delay line is not
making a good ground connection,maybe a loose ground screw on a PCB.
Click to expand...
Any hints on where to look? I do have a manual of sorts. The cal
procedures are legible but not the schematics.

2. There is no response to X in X-Y mode. The beam is stuck at the
left
edge of the screen. The channel 1 controls have no effect and the
horizontal position only has a minor effect noticeable when pushing
the beam finder button.

Thanks.

Perhaps a coax Peltola center pin was bent over instead of it's proper
insertion in the PCB receptacle.I cannot recall if the time/div knob has to
also be in X-Y mode for this function to work on this model.If so,could be
a broken LF cam switch contact(small phosphor-bronze switch contact under
the time/div cam drum)
Click to expand...
The time/div appears to be the only control that should be needed to
enable X-Y mode in the fully counterclockwise position.

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 at repairfaq.org. Thanks.
 
Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in message news:<6w65ib5zcx.fsf@saul.cis.upenn.edu>...
Jim Yanik <jyanik@abuse.gov> writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6wfzhg6lvs.fsf@saul.cis.upenn.edu:

I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces
independent
of vertical amplifier gain settings. It's about 1/2 mm in height.

Could be a HF cap adjustment gone bad;those tiny ceramic trimmer caps
developed a 'black oxide' on the underside,insulating the rotor from the
solder tab.Or the HF cal is off,or the ground on the delay line is not
making a good ground connection,maybe a loose ground screw on a PCB.

Any hints on where to look? I do have a manual of sorts. The cal
procedures are legible but not the schematics.
Click to expand...
Sam,

One quick thing to check:

If there are screws that hold the attenuator switches' metal shields
to the circuit board, as in the 465, make sure that they are tight and
that everything there is making good contact. I've seen similar
problems, on quite a few 465 scopes, that went away when one or both
of those screws were tightened, although usually the frequencies
involved were much higher.

Also:

You can also try shorting the delay line, where it leaves the rear of
the vertical preamp/attenuator board, and check if the ripple is gone.
If it IS gone, the problem is probably on the vertical
preamp/attenuator board. If the ripple is still there, the problem is
probably farther downstream, maybe on the vertical amplifier board.

And:

If the 465B has the same tiny gold switch contacts as the 465 and 475,
for the BW-limiter and the Trigger View switches, near the rear of the
v preamp/atten board, try cleaning them by (carefully) inserting a
small strip of clean white paper under them, adding a few drops of 91%
(or the higher the better) isopropyl alcohol, lowering the contact,
and pulling the paper out, a few times for each contact. The same
thing can be done for the attenuator switches' contacts, if you remove
their metal shields and then pull straight up on each of the
attenuator blocks to remove them.

If you need a schematic or two emailed to you, just let me know. I
have a scanned 465B manual that may have better ones than you have
now. I also sell the service manuals on CDs. But your posts, and
website, etc, have helped me so much in the past that I'll mail you
one for the asking.

Good luck.

Regards,

Tom Gootee

http://www.fullnet.com/u/tomg (Good used test equipment)

2. There is no response to X in X-Y mode. The beam is stuck at the
left
edge of the screen. The channel 1 controls have no effect and the
horizontal position only has a minor effect noticeable when pushing
the beam finder button.

Thanks.

Perhaps a coax Peltola center pin was bent over instead of it's proper
insertion in the PCB receptacle.I cannot recall if the time/div knob has to
also be in X-Y mode for this function to work on this model.If so,could be
a broken LF cam switch contact(small phosphor-bronze switch contact under
the time/div cam drum)

The time/div appears to be the only control that should be needed to
enable X-Y mode in the fully counterclockwise position.

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 at repairfaq.org. Thanks.
Click to expand...
 
tomg@fullnet.com (Thomas P. Gootee) writes:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in
news:6wfzhg6lvs.fsf@saul.cis.upenn.edu:

I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces
independent
of vertical amplifier gain settings. It's about 1/2 mm in height.

One quick thing to check:

If there are screws that hold the attenuator switches' metal shields
to the circuit board, as in the 465, make sure that they are tight and
that everything there is making good contact. I've seen similar
problems, on quite a few 465 scopes, that went away when one or both
of those screws were tightened, although usually the frequencies
involved were much higher.

Also:

You can also try shorting the delay line, where it leaves the rear of
the vertical preamp/attenuator board, and check if the ripple is gone.
If it IS gone, the problem is probably on the vertical
preamp/attenuator board. If the ripple is still there, the problem is
probably farther downstream, maybe on the vertical amplifier board.
Click to expand...
I think I mentioned that it was present on all gain ranges and on both
channels equally high (about 1/2 mm) on the screen.

One thing I did notice is that it was absent on the "trigger view"
displayed line.

And:

If the 465B has the same tiny gold switch contacts as the 465 and 475,
for the BW-limiter and the Trigger View switches, near the rear of the
v preamp/atten board, try cleaning them by (carefully) inserting a
small strip of clean white paper under them, adding a few drops of 91%
(or the higher the better) isopropyl alcohol, lowering the contact,
and pulling the paper out, a few times for each contact. The same
thing can be done for the attenuator switches' contacts, if you remove
their metal shields and then pull straight up on each of the
attenuator blocks to remove them.
Click to expand...
As far as I can tell, there has been absolutely no indication of flakey
switches or controls on any functions. Whether that's an indication that
a dirty switch isn't to blame, I don't know though.

If you need a schematic or two emailed to you, just let me know. I
have a scanned 465B manual that may have better ones than you have
now. I also sell the service manuals on CDs. But your posts, and
website, etc, have helped me so much in the past that I'll mail you
one for the asking.
Click to expand...
Thanks. If the schematics are indeed legible, I would appreciate
a schematic. I have the cal procedures and they are legible but
the scanned schematics are mediocre resolution.

--- 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 at repairfaq.org. Thanks.
 
One indication of bad trimmer caps is that when adjusted,they seem to have
no effect.I've even seen the adj.screw head turn while the rotor disc
stayed put.

Also,bad decoupling caps(both glass-ceramic and epoxy-tantalum) can cause
HF oscillations,on the PS supply lines,and then the HF gets into both
channels.Scoping the vert.preamp supply points will show this
problem.Finding the exact cap is a PITA.

--
Jim Yanik,NRA member
jyanik-at-kua.net
 
Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in message
<snipped>
The time/div appears to be the only control that should be needed to
enable X-Y mode in the fully counterclockwise position.
--------------------------------
Click to expand...
Sam,

I think that you ALSO have to have **Channel 2** selected, for X-Y mode.

- Tom Gootee
--------------------------------
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 at repairfaq.org. Thanks.
Click to expand...
 
tomg@fullnet.com (Thomas P. Gootee) wrote in
news:11915d6.0310271755.269f451c@posting.google.com:

Sam Goldwasser <sam@saul.cis.upenn.edu> wrote in message
snipped
The time/div appears to be the only control that should be needed to
enable X-Y mode in the fully counterclockwise position.
--------------------------------
Sam,

I think that you ALSO have to have **Channel 2** selected, for X-Y
mode.

- Tom Gootee
Click to expand...
That's what I thought,too.
Although some scopes and sweep plugins use the external trigger input for
the X channel input,IIRC,with only one level of sensitivity(V/div range).

--
Jim Yanik,NRA member
jyanik-at-kua.net
 
I have the manual, and you're welcome to some scans, but it
sounds like Thomas already has you covered.

BTW, on my 465B, I've had to change out two of the bridge
rectifiers packs, so check PS voltages first if you haven't
already done this.

I also have CR1483 highlighted in yellow, which is my color
code for a bad part, however I think the symptom for this
part was loss of beam current as it's part of the tube biasing
scheme on the interface board.

As I vaguely recall, I think that I lost deflection from loss of -8V
when one of the bridges went bad.

It doesn't sound like any of these are your problems,
but they may be in the future, so I'm telling you anyway.

Also, I've had numerous other minor problems that were
solved by cleaning switches and contacts.

I think Jim advised me ( some time ago) to only use alcohol
to clean the gold contacts in the vertical preamps section.

Good luck

--
Regards,
Dave Moore
Products Foundry Support http://www.productsfoundry.com/
Innovative and ever improving software.





"Sam Goldwasser" wrote
I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces independent
of vertical amplifier gain settings. It's about 1/2 mm in height.

2. There is no response to X in X-Y mode. The beam is stuck at the left
edge of the screen. The channel 1 controls have no effect and the
horizontal position only has a minor effect noticeable when pushing the
beam finder button.

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 at repairfaq.org. Thanks.
Click to expand...
 
Checking my notes, here's another one you may run into some day,

PNP xstr's Q650 and Q652 in the A&B Trigger Generator circuit
bad caused loss of horizontal deflection.


--
Regards,
Dave Moore
Products Foundry Support http://www.productsfoundry.com/
Innovative and ever improving software.







"Sam Goldwasser" <sam@saul.cis.upenn.edu> wrote in message
news:6wfzhg6lvs.fsf@saul.cis.upenn.edu...
I have a Tek465B with a couple of minor problems:

1. There is a low level ripple, about 100 kHz, on both traces independent
of vertical amplifier gain settings. It's about 1/2 mm in height.

2. There is no response to X in X-Y mode. The beam is stuck at the left
edge of the screen. The channel 1 controls have no effect and the
horizontal position only has a minor effect noticeable when pushing the
beam finder button.

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 at repairfaq.org. Thanks.
Click to expand...
 
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