Hi,

On a tek 2230 in non-store mode, the displayed signal becomes compressed when position is moved to the left.

So if I have a 5K square wave displayed at .1 Ms the first 1/2 of the wave will be 60% the width if I move it to the right. It also looks like brighter.

+==+==+==+==+==+==+==+==+==+==+
---___---___--- <moved to right>

+--- Short and brighter.
V
==___---___---

What needs adjusting

David,
Is the display also distorted in store mode? If so, it might be a loose connection to one of the horizontal deflection pins of the CRT.
--John Gord

Does the trace compress to the left with both timebases?

For the part which is not compressed, is the timebase still in
calibration?

Unfortunately I suspect the problem is going to be somewhere around
U760 on schematic 7 but I would also check the levels of STORE and NOT
STORE to the right of U760 on schematic 7.

On Mon, 23 Jan 2012 19:31:20 -0000, "david_s5y" <david_s5@...>
wrote:

On a tek 2230 in non-store mode, the displayed signal becomes compressed when position is moved to the left.

So if I have a 5K square wave displayed at .1 Ms the first 1/2 of the wave will be 60% the width if I move it to the right. It also looks like brighter.

+==+==+==+==+==+==+==+==+==+==+
---___---___--- <moved to right>

+--- Short and brighter.
V
==___---___---

What needs adjusting

As others have suggested, check the physical connections at the CRT before
you do anything else.
tom jobe...

Thanks for the suggestion. I have pushed on the connector. It did not help.

Store mode is currently not working. I currently have Q2105 removed.

I am awaiting the arrival of another scope to troubleshoot the storage problem. This could be related.

If I inject a signal at the emitter of Q2105 I can see the signal on the display and it does not compress. But I have not been able to verify the signal path from the Ch 1 and 2 inputs in store mode.

In non Store the compression occurs on both channels A and B time bases.

It is like the H position is off 1/2 a graticule to the right and the trace is retracing. Like on a TV. Is there H Postion Adjustment?

On Tue, 24 Jan 2012 15:57:34 -0000, "david_s5y" <david_s5@...>
wrote:

Thanks for the suggestion. I have pushed on the connector. It did not help.

Store mode is currently not working. I currently have Q2105 removed.

Gah! I wish you had posted that initially. My suggestions assumed
store mode worked or at least that it and the readout lacked any
display problems.

I am awaiting the arrival of another scope to troubleshoot the storage problem. This could be related.

If I inject a signal at the emitter of Q2105 I can see the signal on the display and it does not compress. But I have not been able to verify the signal path from the Ch 1 and 2 inputs in store mode.

I would help if you said where Q2105 is. The service manual lists
parts by assembly and there are 24 of them.

In non Store the compression occurs on both channels A and B time bases.

It is like the H position is off 1/2 a graticule to the right and the trace is retracing. Like on a TV. Is there H Postion Adjustment?

I do not believe this is an adjustment problem. I have seen this
happen before when a CRT output amplifier went into limiting because
of an open load resistor. The 2230 Horizontal Output Amplifier uses
shunt feedback and a constant current load so I would check the
resistors and then the transistors. R786, Q789, R776, and Q779 are
where I would start. I might look for the distortion in the
horizontal signal chain starting from the CRT and moving back toward
the Horizontal Preamp.

Is the readout similarly warped? If not then it is not the Horizontal
Output Amplifier.

Yes for Both A and B.

Yes the timebase still in calibration for the part which is not compressed.

At U7202A/B
STORE .72 and 7.2 (this is lower then on schemtic 7.59)
/STORE .55 and 7.2 (this is lower then on schemtic 7.45)

Those are not the problem then. I was thinking that if the
multiplexing diodes where not switching completely it would cause
clipping in analog mode while allowing the readout and digital display
to work correctly.

On Tue, 24 Jan 2012 16:55:30 -0000, "david_s5y" <david_s5@...>
wrote:

Yes for Both A and B.

Yes the timebase still in calibration for the part which is not compressed.

At U7202A/B
STORE .72 and 7.2 (this is lower then on schemtic 7.59)
/STORE .55 and 7.2 (this is lower then on schemtic 7.45)

--- In TekScopes@..., David <davidwhess@...> wrote:

Does the trace compress to the left with both timebases?

For the part which is not compressed, is the timebase still in
calibration?

Unfortunately I suspect the problem is going to be somewhere around
U760 on schematic 7 but I would also check the levels of STORE and NOT
STORE to the right of U760 on schematic 7.

On Mon, 23 Jan 2012 19:31:20 -0000, "david_s5y" <david_s5@...>
wrote:

On a tek 2230 in non-store mode, the displayed signal becomes compressed when position is moved to the left.

So if I have a 5K square wave displayed at .1 Ms the first 1/2 of the wave will be 60% the width if I move it to the right. It also looks like brighter.

I have repaired the storage functions and am now trying to resolve this display issue.

Here is a video

That shows the issue. It only appear in NON-Store mode.

I start in Store mode and show it works, then switch to NON store show the issue and then change the time base and then return to store.

Since it works in Store mode am I correct to think that rules out the physical connections at the CRT?

But can the CRT output amplifier be going into limiting for only the non store?

How is the horizontal timing generated?

I am lost, please fire some suggestions my way.

David

David,
The stored signal is switched in fairly late in the horizontal circuit. Take a look at the schematic (ko4bb.com if you don't have a better copy). The digital signal is switched in at the "Horizontal Mux", but the analog horizontal comes in through the "Horizontal Preamp" section. Check voltages and waveforms in that section. Note that the A and B sweeps come in through almost the same path. Does the B sweep also have the compression on the left side?

--John Gord

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The storage and readout vectors are inserted between the horizontal
preamplifier and the horizontal output amplifier so the problem will
be the horizontal multiplexor on schematic 7 or earlier. The
horizontal output amplifier should be fine. I suspect the sweep
outputs up to U760 are fine as well.

As a test, switch the oscilloscope to delayed mode and see how the B
timebase which uses a separate parallel circuit path works.

What are the marked voltages around the horizontal multiplexor in
store and non-store mode? What are the marked voltages around U760 in
store and non-store mode?

On Sat, 11 Feb 2012 18:07:21 -0000, "david_s5y" <david_s5@...>
wrote:

I have repaired the storage functions and am now trying to resolve this display issue.

Here is a video

That shows the issue. It only appear in NON-Store mode.

I start in Store mode and show it works, then switch to NON store show the issue and then change the time base and then return to store.

Since it works in Store mode am I correct to think that rules out the physical connections at the CRT?

That rules out the physical connections to the CRT and also rules out
the horizontal output amplifier.

But can the CRT output amplifier be going into limiting for only the non store?

No.

How is the horizontal timing generated?

In non-store mode it is generated in the A sweep generator (schematic
5) and in the B sweep generator (schematic 6) but neither of those
have anything to do with the position control.

I was hopping you were going to chime in. I always learn from your posts. Thank you David.

There was one oddity. That does not match the schematic. But it looked like it was done in the factory. The collector Q732 had it's collector tied to Q742's collector and pin 10 does did not have any signal on it , yet delay works fine. Is yours like that too?

David

I learned a lot about the 2230 when I spent weeks tracking down that
noise problem with mine so I generally feel comfortable diagnosis it
and the related models over email. Your video helped a lot.

The big failure modes which I always try to check first are mechanical
controls including potentiometers and switches, open resistors, and
bad solder joints or cracked traces. I have a 7B92A that caught on
fire from a shorted tantalum but it still does not work.

On Sun, 12 Feb 2012 00:17:05 -0000, "david_s5y" <david_s5@...>
wrote:

I was hopping you were going to chime in. I always learn from your posts. Thank you David.

--- In TekScopes@..., David <davidwhess@...> wrote:

The storage and readout vectors are inserted between the horizontal
preamplifier and the horizontal output amplifier so the problem will
be the horizontal multiplexor on schematic 7 or earlier. The
horizontal output amplifier should be fine. I suspect the sweep
outputs up to U760 are fine as well.

As a test, switch the oscilloscope to delayed mode and see how the B
timebase which uses a separate parallel circuit path works.

What are the marked voltages around the horizontal multiplexor in
store and non-store mode? What are the marked voltages around U760 in
store and non-store mode?

On Sat, 11 Feb 2012 18:07:21 -0000, "david_s5y" <david_s5@...>
wrote:

I have repaired the storage functions and am now trying to resolve this display issue.

Here is a video

That shows the issue. It only appear in NON-Store mode.

I start in Store mode and show it works, then switch to NON store show the issue and then change the time base and then return to store.

Since it works in Store mode am I correct to think that rules out the physical connections at the CRT?

That rules out the physical connections to the CRT and also rules out
the horizontal output amplifier.

But can the CRT output amplifier be going into limiting for only the non store?

No.

How is the horizontal timing generated?

In non-store mode it is generated in the A sweep generator (schematic
5) and in the B sweep generator (schematic 6) but neither of those
have anything to do with the position control.

If mine are like that I have not noticed. Functionally it should not
matter which sweep inputs are used since the sweep signals are current
switched using CR742 and CR732 externally which is exactly how U760 is
designed to operate so they could both go to one or to the separate
sweep inputs. In a dual timebase design like a 4 bay 7000 series,
each timebase bay would go to a separate input I think. The
155-0124-00 horizontal preamplifier is in the Tek-Made Integrated
Circuits Manual.

The unused input should be pulled low. Isn't R733 still in place?

On Sun, 12 Feb 2012 00:20:45 -0000, "david_s5y" <david_s5@...>
wrote:

There was one oddity. That does not match the schematic. But it looked like it was done in the factory. The collector Q732 had it's collector tied to Q742's collector and pin 10 does did not have any signal on it , yet delay works fine. Is yours like that too?

David

--- In TekScopes@..., David <davidwhess@...> wrote:

The storage and readout vectors are inserted between the horizontal
preamplifier and the horizontal output amplifier so the problem will
be the horizontal multiplexor on schematic 7 or earlier. The
horizontal output amplifier should be fine. I suspect the sweep
outputs up to U760 are fine as well.

As a test, switch the oscilloscope to delayed mode and see how the B
timebase which uses a separate parallel circuit path works.

What are the marked voltages around the horizontal multiplexor in
store and non-store mode? What are the marked voltages around U760 in
store and non-store mode?

On Sat, 11 Feb 2012 18:07:21 -0000, "david_s5y" <david_s5@...>
wrote:

I have repaired the storage functions and am now trying to resolve this display issue.

Here is a video

That shows the issue. It only appear in NON-Store mode.

I start in Store mode and show it works, then switch to NON store show the issue and then change the time base and then return to store.

Since it works in Store mode am I correct to think that rules out the physical connections at the CRT?

That rules out the physical connections to the CRT and also rules out
the horizontal output amplifier.

But can the CRT output amplifier be going into limiting for only the non store?

No.

How is the horizontal timing generated?

In non-store mode it is generated in the A sweep generator (schematic
5) and in the B sweep generator (schematic 6) but neither of those
have anything to do with the position control.

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