2215 Tektronix oscilloscope vertical adjust problem

M

Matt

Guest
A work colleague wanted me to test a pre-amp stage of a valve amp that
he his currently working on.

I set my sigen up and wired it up to the oscilloscope for some
benchmark readings. It all worked as expected, duty called and had to
leave it until lunch before I could test the amp. I left the
oscilloscope on connected to the signal generator.
Throughout the morning the trace drifted vertically unit I couldn't
adjust it down any further. it the continued to rise right off the
screen.
The trace now sits right at the top edge of the screen, just about
catch the shadow of the trace if the intensity is turned up quite
high.

My initial thought that something had over heated, so I turned it off
for a couple of hours. This had no effect.

So the bottom line is the oscilloscope is broke. Has anyone had
problems like this before or could anyone suggest any tests that I
could perform to track down the problem?

Thanks!
 
mnc_co_uk@yahoo.co.uk (Matt) wrote in
news:9ecd996.0501171427.8d09bf8@posting.google.com:

A work colleague wanted me to test a pre-amp stage of a valve amp that
he his currently working on.

I set my sigen up and wired it up to the oscilloscope for some
benchmark readings. It all worked as expected, duty called and had to
leave it until lunch before I could test the amp. I left the
oscilloscope on connected to the signal generator.
Throughout the morning the trace drifted vertically unit I couldn't
adjust it down any further. it the continued to rise right off the
screen.
The trace now sits right at the top edge of the screen, just about
catch the shadow of the trace if the intensity is turned up quite
high.

My initial thought that something had over heated, so I turned it off
for a couple of hours. This had no effect.

So the bottom line is the oscilloscope is broke. Has anyone had
problems like this before or could anyone suggest any tests that I
could perform to track down the problem?

Thanks!
Click to expand...
1.Do you have a service manual? If not,you need one.
2.Does the problem occur on one or both input channels?
3.First check all the LV supplies to insure they are correct.

This is not a problem I've encounted before.(not a 'common' problem)

--
Jim Yanik
jyanik
at
kua.net
 
Trying to locate a service manual for it now. Yes, it has effected both
channels of the scope.
When the scope was on it's way out I was able to correct it using the
vertical adjust but when I moved the trace to the lower end of the
screen I noticed that the sine wave trace reduced in size(at this point
in time I couldnt move it down any further than the first 1/4 of the
screen). Moving the trace closer to the top of the screen caused the
trace to display it's normal size. I could perform this only until the
trace headed north and remained there.

Jim Yanik wrote:
mnc_co_uk@yahoo.co.uk (Matt) wrote in
news:9ecd996.0501171427.8d09bf8@posting.google.com:

A work colleague wanted me to test a pre-amp stage of a valve amp
that
he his currently working on.

I set my sigen up and wired it up to the oscilloscope for some
benchmark readings. It all worked as expected, duty called and had
to
leave it until lunch before I could test the amp. I left the
oscilloscope on connected to the signal generator.
Throughout the morning the trace drifted vertically unit I couldn't
adjust it down any further. it the continued to rise right off the
screen.
The trace now sits right at the top edge of the screen, just about
catch the shadow of the trace if the intensity is turned up quite
high.

My initial thought that something had over heated, so I turned it
off
for a couple of hours. This had no effect.

So the bottom line is the oscilloscope is broke. Has anyone had
problems like this before or could anyone suggest any tests that I
could perform to track down the problem?

Thanks!


1.Do you have a service manual? If not,you need one.
2.Does the problem occur on one or both input channels?
3.First check all the LV supplies to insure they are correct.

This is not a problem I've encounted before.(not a 'common' problem)

--
Jim Yanik
jyanik
at
kua.net
Click to expand...
 
"mnc_co_uk@yahoo.co.uk" <mnc_co_uk@yahoo.co.uk> wrote in
news:1106069204.683197.144280@c13g2000cwb.googlegroups.com:

Trying to locate a service manual for it now. Yes, it has effected both
channels of the scope.
When the scope was on it's way out I was able to correct it using the
vertical adjust but when I moved the trace to the lower end of the
screen I noticed that the sine wave trace reduced in size(at this point
in time I couldnt move it down any further than the first 1/4 of the
screen). Moving the trace closer to the top of the screen caused the
trace to display it's normal size. I could perform this only until the
trace headed north and remained there.
Click to expand...
I would look at the resistors in the vertical output stage.There have been
resistors that changed in value(precision metal film),and that would affect
gain and positioning.I'm thinking of the 1/2W resistors in the output
stages,near where the CRT vertical leads join the main PCB.
Accoring to my manual,they should be 340 ohm,1/2W MF,marked
R378,379,388,389 on the PCB.

If you short the delay line at the front of the vert. ouput amp,the trace
should approximately center if the output amp is OK.

--
Jim Yanik
jyanik
at
kua.net
 
One more thing while you're at it;a common failure;the focus string
resistors increase in value until they open,and your focus goes bad. They
were modded by TEK to use carbon composition 1 Meg 1/2w instead of the
usual 1/2w carbon film,they are around the HV multiplier on the main
board,5 of them;R878,879,880,881,882,884.



--
Jim Yanik
jyanik
at
kua.net
 
Thanks for all of your input so far. I'm having a service manual
uploaded to me tonight. I'll checkout what you have suggested and come
back with some news.

Matt
 
"mnc_co_uk@yahoo.co.uk" <mnc_co_uk@yahoo.co.uk> wrote in
news:1106165143.963240.128150@c13g2000cwb.googlegroups.com:

Thanks for all of your input so far. I'm having a service manual
uploaded to me tonight. I'll checkout what you have suggested and come
back with some news.

Matt
Click to expand...
The circuit description is very good,I recommend reading it.

--
Jim Yanik
jyanik
at
kua.net
 
Is this a dual-channel oscilloscope? Both channels affected? Affected
about the same regardless of how you set the vertical sensitivity? (Small
shifts up and down don't count.)

Check 2 things:

- Circuitry around the vertical position control;

- The vertical output stage, which is almost certainly push-pull and sounds
as if it's losing one of its two transistors.

If the problem goes away as you turn down the vertical sensitivity, then
check closer to the inputs.

I'm not familiar with the 2215. This is from vague memory of other
scopes...
 
Found a supplier in the UK www.dalbani.co.uk. They had the BFR 96 in
stock for Ł0.40.
Ordered 10 for good measure

Thanks to everyone that helped

Matt
 
"Jim Yanik" <jyanik@abuse.gov.> wrote in message
news:Xns95E3B875EA7A4jyanikkuanet@129.250.170.83...
The circuit description is very good,I recommend reading it.
Click to expand...
Mr Yanik:

What service manual for a tek scope would you recommend as the best circuit
description for a good modern analog scope? By analog i mean without
one-block-of-epoxy-does-all-this and another-block-does-that, by modern i
mean: no valves.
I've read the 545 service manual and was amazed at the detail they went.
I would like to read something similar but more recent.

Best regards

--
Steve Sousa
 
John Crighton wrote:
On 26 Jan 2005 01:27:57 GMT, Jim Yanik <jyanik@abuse.gov.> wrote:


"Steve Sousa" <etsteve@yahoo.com> wrote in
news:35nvshF4pctsqU1@individual.net:


"Jim Yanik" <jyanik@abuse.gov.> wrote in message
news:Xns95E3B875EA7A4jyanikkuanet@129.250.170.83...

The circuit description is very good,I recommend reading it.


Mr Yanik:

What service manual for a tek scope would you recommend as the best
circuit description for a good modern analog scope? By analog i mean
without one-block-of-epoxy-does-all-this and another-block-does-that,
by modern i mean: no valves.
I've read the 545 service manual and was amazed at the detail they
went. I would like to read something similar but more recent.

Best regards


The last and best analog scope TEK ever made was the 2445/65 series,but
those scopes used TEK-made hybrid ICs and were rather complicated,using a
digital front panel control of analog circuits.Still a good study,though.

The next scope would be the simple 2213/15/35 series of scopes.

Then the biggest seller TEK ever had;the 465 scope.This may be the easiest
manual to obtain.

All of these had excellent,detailed circuit descriptions.

--
Jim Yanik



Hello Steve,
http://bama.sbc.edu/
here you will find a ton of interesting reading.

Two of the manuals that Jim mentioned are listed here
http://bama.sbc.edu/tektroni.htm
The 2213 and 465

I have no idea if they are complete or not so don't
get too excited. :)

Regards,
John Crighton
Sydney
Click to expand...

After searching endlessly for a service manual for an Iwatsu DS6121
DSO (eventually found one, in english, imagine that!) here's my long
list of manual sources:

Charts Site:
ftp://anonymous:look@charts.ath.cx/

Manuals:
http://www.yourmanualsource.com
http://www.w7fg.com/index.html
http://www.manualmerchant.com
http://www.manualsplus.com/
http://www.ntis.gov/databases/armypub.htm
http://ac6v.com/manuals.htm
http://bama.sbc.edu/
http://www.bec-ccl.com/
http://www.manualmall.com/
http://www.mauritron.co.uk/mauritron/manuals_w.htm
http://www.spies.com/~dd/manavail.html
http://www.hi-manuals.com/HomePage.htm
http://www.one-electron.com/FC_TestEquipment.html
http://www.manualserver.com/transievers.htm
http://www.testequipmentcanada.com/w.html
http://www.usimperio.com/consolidated/search.htm
http://www.cooke-int.com/manuals/
http://www.sarrio.com/sarrio/rsman4.html
http://www.belar.com/ib/
http://www.chiark.greenend.org.uk/scopes/resource.html

Ed Matsuda (send him an email no site yet)
ematsuda.at.earthlink.dot.net or ematsuda.at.themall.dot.net
 
These are quite complete, so you can get happy with these. Note that
the 465 is a 465B, and you need a (free downloadable) djvu viewer. Be
assured, it is worth it.

Other source ist www.teknetelectronics.com for free download.
hth,
Andreas
 
In some mesages back several people sent urls for tek scope manual...

Hello:

Thank all of you guys who sent me those addresses, i got the manual for
465m, unfortunately it doesn't have the schematic, which hampers a lot of
the understanding.
Maybe i'll buy one for the 22xx series in one of the sites mentioned.

I'll keep looking.

Best Regards.

--
Steve Sousa
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top