485 No Trace - some progress, question


Robert Simpson
 

Yes,
With further review of the schematic, I realized I was going into the focus control. Looking back, I see pin 8 of U1560 affects the Z out test point. Testing Pin 8 on the working scope varies about one volt. Pin 8 on the non working scope doesn't vary at all. I re-socketed this IC and the surrounding transistors. No effect.
Measurements for U1560:

U1560
Pin Working Non Working
1 -62mv +26mv
2 +1.1V +1.1V
3 +0.7V +0.3V
4 +51mv +48mv
5 +4.9mv +1.06V
6 +0.78V +0.79V
7 +0.96V +1.0V
8 +13.9V +14V
9 +3.6mv -1.0mv
10 +4.25V +4.2V
11 +14.9V +15V
12 +5.0V +4.9V
13 +4.9V +4.9V
14 +98mv +99mv
15 -187mv +928mv
16 -138mv +282mv

Question, given the above measurements, would it be safe to swap in the working U1550 without risk of damage?

Bob

--- In TekScopes@yahoogroups.com, David wrote:

I do not envy you trying to work through that z-axis amplifier. Having
a working 485 for comparison will help a lot.

R1703 is part of the focus circuit path. Z In (TP1741) and Z Out
(TP1781) are the input and output of the z-axis amplifier.

If the z-axis amplifier transistors are socketted, I would pull and
check them individually for shorts and opens using the diode test
function on my multimeter.

On Wed, 30 Jan 2013 16:27:26 -0000, "Robert"
wrote:

Last night tried the Grid Bias adjustment procedure item 10 on page 5-10 and found a problem. The non working scope has no change at the Z Out DC test point when adjusting the A channel intensity. My working 485 changes as expected when adjusting the front panel A channel intensity control. The non working scope stays the same at about 8.2 volts. 8.2 volts is about the same as the working scope with the front panel A channel intensity all the way down. So the beam must be in cutoff condition.

So far have traced to R1703 and the voltage varies OK to that point (same as the working 485). I will continue tracing today.
Bob


Robert Simpson
 

That is, U1560

--- In TekScopes@yahoogroups.com, "Robert" wrote:

Yes,
With further review of the schematic, I realized I was going into the focus control. Looking back, I see pin 8 of U1560 affects the Z out test point. Testing Pin 8 on the working scope varies about one volt. Pin 8 on the non working scope doesn't vary at all. I re-socketed this IC and the surrounding transistors. No effect.
Measurements for U1560:

U1560
Pin Working Non Working
1 -62mv +26mv
2 +1.1V +1.1V
3 +0.7V +0.3V
4 +51mv +48mv
5 +4.9mv +1.06V
6 +0.78V +0.79V
7 +0.96V +1.0V
8 +13.9V +14V
9 +3.6mv -1.0mv
10 +4.25V +4.2V
11 +14.9V +15V
12 +5.0V +4.9V
13 +4.9V +4.9V
14 +98mv +99mv
15 -187mv +928mv
16 -138mv +282mv

Question, given the above measurements, would it be safe to swap in the working U1550 without risk of damage?

Bob


--- In TekScopes@yahoogroups.com, David wrote:

I do not envy you trying to work through that z-axis amplifier. Having
a working 485 for comparison will help a lot.

R1703 is part of the focus circuit path. Z In (TP1741) and Z Out
(TP1781) are the input and output of the z-axis amplifier.

If the z-axis amplifier transistors are socketted, I would pull and
check them individually for shorts and opens using the diode test
function on my multimeter.

On Wed, 30 Jan 2013 16:27:26 -0000, "Robert"
wrote:

Last night tried the Grid Bias adjustment procedure item 10 on page 5-10 and found a problem. The non working scope has no change at the Z Out DC test point when adjusting the A channel intensity. My working 485 changes as expected when adjusting the front panel A channel intensity control. The non working scope stays the same at about 8.2 volts. 8.2 volts is about the same as the working scope with the front panel A channel intensity all the way down. So the beam must be in cutoff condition.

So far have traced to R1703 and the voltage varies OK to that point (same as the working 485). I will continue tracing today.
Bob


 

The Tek-Made Integrated Circuits Catalog has details and an internal
schematic for the 155-0012-00 Z-Axis Logic IC.

Pins 5 and 15 are high impedance logic inputs so the slightly higher
voltages you measured should not damage a replacement IC but before
trying a swap, I would check the circuits that generate the voltages
going into pins 5 and 15 although I am not sure what I would look for.
There is no reason for those pins to be high.

I would also check the area around U1585.

I do not see any evidence that U1560 is bad. I suspect an earlier
problem is keeping the CRT beam blanked.

On Wed, 30 Jan 2013 19:37:58 -0000, "Robert"
<go_boating_fast@yahoo.com> wrote:

Yes,
With further review of the schematic, I realized I was going into the focus control. Looking back, I see pin 8 of U1560 affects the Z out test point. Testing Pin 8 on the working scope varies about one volt. Pin 8 on the non working scope doesn't vary at all. I re-socketed this IC and the surrounding transistors. No effect.
Measurements for U1560:

U1560
Pin Working Non Working
1 -62mv +26mv
2 +1.1V +1.1V
3 +0.7V +0.3V
4 +51mv +48mv
5 +4.9mv +1.06V
6 +0.78V +0.79V
7 +0.96V +1.0V
8 +13.9V +14V
9 +3.6mv -1.0mv
10 +4.25V +4.2V
11 +14.9V +15V
12 +5.0V +4.9V
13 +4.9V +4.9V
14 +98mv +99mv
15 -187mv +928mv
16 -138mv +282mv

Question, given the above measurements, would it be safe to swap in the working U1550 without risk of damage?

Bob


--- In TekScopes@yahoogroups.com, David wrote:

I do not envy you trying to work through that z-axis amplifier. Having
a working 485 for comparison will help a lot.

R1703 is part of the focus circuit path. Z In (TP1741) and Z Out
(TP1781) are the input and output of the z-axis amplifier.

If the z-axis amplifier transistors are socketted, I would pull and
check them individually for shorts and opens using the diode test
function on my multimeter.

On Wed, 30 Jan 2013 16:27:26 -0000, "Robert"
wrote:

Last night tried the Grid Bias adjustment procedure item 10 on page 5-10 and found a problem. The non working scope has no change at the Z Out DC test point when adjusting the A channel intensity. My working 485 changes as expected when adjusting the front panel A channel intensity control. The non working scope stays the same at about 8.2 volts. 8.2 volts is about the same as the working scope with the front panel A channel intensity all the way down. So the beam must be in cutoff condition.

So far have traced to R1703 and the voltage varies OK to that point (same as the working 485). I will continue tracing today.
Bob


Dave Daniel
 

Where would one find a copy of the "Tek-Made  Integrated Circuits Catalog"?

Cheers,
Dave


On 1/30/2013 4:09 PM, David wrote:
 

The Tek-Made Integrated Circuits Catalog has details and an internal
schematic for the 155-0012-00 Z-Axis Logic IC.

Pins 5 and 15 are high impedance logic inputs so the slightly higher
voltages you measured should not damage a replacement IC but before
trying a swap, I would check the circuits that generate the voltages
going into pins 5 and 15 although I am not sure what I would look for.
There is no reason for those pins to be high.

I would also check the area around U1585.

I do not see any evidence that U1560 is bad. I suspect an earlier
problem is keeping the CRT beam blanked.

On Wed, 30 Jan 2013 19:37:58 -0000, "Robert"
go_boating_fast@...> wrote:

>Yes,
>With further review of the schematic, I realized I was going into the focus control. Looking back, I see pin 8 of U1560 affects the Z out test point. Testing Pin 8 on the working scope varies about one volt. Pin 8 on the non working scope doesn't vary at all. I re-socketed this IC and the surrounding transistors. No effect.
>Measurements for U1560:
>
>U1560
>Pin Working Non Working
>1 -62mv +26mv
>2 +1.1V +1.1V
>3 +0.7V +0.3V
>4 +51mv +48mv
>5 +4.9mv +1.06V
>6 +0.78V +0.79V
>7 +0.96V +1.0V
>8 +13.9V +14V
>9 +3.6mv -1.0mv
>10 +4.25V +4.2V
>11 +14.9V +15V
>12 +5.0V +4.9V
>13 +4.9V +4.9V
>14 +98mv +99mv
>15 -187mv +928mv
>16 -138mv +282mv
>
>Question, given the above measurements, would it be safe to swap in the working U1550 without risk of damage?
>
>Bob
>
>
>--- In TekScopes@..., David wrote:
>>
>> I do not envy you trying to work through that z-axis amplifier. Having
>> a working 485 for comparison will help a lot.
>>
>> R1703 is part of the focus circuit path. Z In (TP1741) and Z Out
>> (TP1781) are the input and output of the z-axis amplifier.
>>
>> If the z-axis amplifier transistors are socketted, I would pull and
>> check them individually for shorts and opens using the diode test
>> function on my multimeter.
>>
>> On Wed, 30 Jan 2013 16:27:26 -0000, "Robert"
>> wrote:
>>
>> >Last night tried the Grid Bias adjustment procedure item 10 on page 5-10 and found a problem. The non working scope has no change at the Z Out DC test point when adjusting the A channel intensity. My working 485 changes as expected when adjusting the front panel A channel intensity control. The non working scope stays the same at about 8.2 volts. 8.2 volts is about the same as the working scope with the front panel A channel intensity all the way down. So the beam must be in cutoff condition.
>> >
>> >So far have traced to R1703 and the voltage varies OK to that point (same as the working 485). I will continue tracing today.
>> >Bob



 

Mine came from aa4df.com - I think Dave H. is negotiating with his widow for his scans.

Regards,
David Partridge
________________________________

From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] On Behalf Of Dave Daniel
Sent: 30 January 2013 23:14
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: 485 No Trace - some progress, question

Where would one find a copy of the "Tek-Made Integrated Circuits Catalog"?

Cheers,
Dave


 

BTW the aa4df.com you currently see is just a domain name sales page, the only relationship to the aa4df.com that used to be is that the new page mentions manuals. It also only seems to work in IE.

Regards,
David Partridge
________________________________

From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] On Behalf Of Dave Daniel
Sent: 30 January 2013 23:14
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: 485 No Trace - some progress, question

Where would one find a copy of the "Tek-Made Integrated Circuits Catalog"?

Cheers,
Dave


Robert Simpson
 

Quick test: I tried IC U1560 in the working scope and got a trace, so it looks like some input is keeping it in blanking mode. On to more circuit analysis and tracing.
Bob

--- In TekScopes@yahoogroups.com, David wrote:

The Tek-Made Integrated Circuits Catalog has details and an internal
schematic for the 155-0012-00 Z-Axis Logic IC.

Pins 5 and 15 are high impedance logic inputs so the slightly higher
voltages you measured should not damage a replacement IC but before
trying a swap, I would check the circuits that generate the voltages
going into pins 5 and 15 although I am not sure what I would look for.
There is no reason for those pins to be high.

I would also check the area around U1585.

I do not see any evidence that U1560 is bad. I suspect an earlier
problem is keeping the CRT beam blanked.

On Wed, 30 Jan 2013 19:37:58 -0000, "Robert"
wrote:

Yes,
With further review of the schematic, I realized I was going into the focus control. Looking back, I see pin 8 of U1560 affects the Z out test point. Testing Pin 8 on the working scope varies about one volt. Pin 8 on the non working scope doesn't vary at all. I re-socketed this IC and the surrounding transistors. No effect.
Measurements for U1560:

U1560
Pin Working Non Working
1 -62mv +26mv
2 +1.1V +1.1V
3 +0.7V +0.3V
4 +51mv +48mv
5 +4.9mv +1.06V
6 +0.78V +0.79V
7 +0.96V +1.0V
8 +13.9V +14V
9 +3.6mv -1.0mv
10 +4.25V +4.2V
11 +14.9V +15V
12 +5.0V +4.9V
13 +4.9V +4.9V
14 +98mv +99mv
15 -187mv +928mv
16 -138mv +282mv

Question, given the above measurements, would it be safe to swap in the working U1550 without risk of damage?

Bob


--- In TekScopes@yahoogroups.com, David wrote:

I do not envy you trying to work through that z-axis amplifier. Having
a working 485 for comparison will help a lot.

R1703 is part of the focus circuit path. Z In (TP1741) and Z Out
(TP1781) are the input and output of the z-axis amplifier.

If the z-axis amplifier transistors are socketted, I would pull and
check them individually for shorts and opens using the diode test
function on my multimeter.

On Wed, 30 Jan 2013 16:27:26 -0000, "Robert"
wrote:

Last night tried the Grid Bias adjustment procedure item 10 on page 5-10 and found a problem. The non working scope has no change at the Z Out DC test point when adjusting the A channel intensity. My working 485 changes as expected when adjusting the front panel A channel intensity control. The non working scope stays the same at about 8.2 volts. 8.2 volts is about the same as the working scope with the front panel A channel intensity all the way down. So the beam must be in cutoff condition.

So far have traced to R1703 and the voltage varies OK to that point (same as the working 485). I will continue tracing today.
Bob


 

I suppose that is good news since U1560 would probably be difficult to
replace. On the other hand, that just moves the problem into the
inscrutable oscilloscope logic.

I would take a close look at the horizontal and vertical mode switches
because they are subject to mechanical failure and those pullup
resistors. Those are easy to check.

Sometimes a pushbutton switch can conduct a static discharge into the
circuits and damage them so I would check any logic ICs directly
connected to them like U1530, U1535, and U1580.

On Thu, 31 Jan 2013 05:39:01 -0000, "Robert"
<go_boating_fast@yahoo.com> wrote:

Quick test: I tried IC U1560 in the working scope and got a trace, so it looks like some input is keeping it in blanking mode. On to more circuit analysis and tracing.

Bob


Robert Simpson
 

Funny, as I was thinking about this while falling asleep, the thought of a stuck front panel switch came to mind, like being in single trace mode or something. It will take me some serious manual reading to figure out the switch/signal circuit effects.
Bob

--- In TekScopes@yahoogroups.com, David wrote:

I suppose that is good news since U1560 would probably be difficult to
replace. On the other hand, that just moves the problem into the
inscrutable oscilloscope logic.

I would take a close look at the horizontal and vertical mode switches
because they are subject to mechanical failure and those pullup
resistors. Those are easy to check.

Sometimes a pushbutton switch can conduct a static discharge into the
circuits and damage them so I would check any logic ICs directly
connected to them like U1530, U1535, and U1580.

On Thu, 31 Jan 2013 05:39:01 -0000, "Robert"
wrote:

Quick test: I tried IC U1560 in the working scope and got a trace, so it looks like some input is keeping it in blanking mode. On to more circuit analysis and tracing.

Bob


Robert Simpson
 

The difference at Pin 5 was just a front panel button. When set the same, both scopes have the same value. Although Pin 15 comes from the delayed sweep control, both scopes are set the same. Now trying to figure out how that circuit works.
Bob

--- In TekScopes@yahoogroups.com, "Robert" wrote:

Funny, as I was thinking about this while falling asleep, the thought of a stuck front panel switch came to mind, like being in single trace mode or something. It will take me some serious manual reading to figure out the switch/signal circuit effects.
Bob
--- In TekScopes@yahoogroups.com, David wrote:

I suppose that is good news since U1560 would probably be difficult to
replace. On the other hand, that just moves the problem into the
inscrutable oscilloscope logic.

I would take a close look at the horizontal and vertical mode switches
because they are subject to mechanical failure and those pullup
resistors. Those are easy to check.

Sometimes a pushbutton switch can conduct a static discharge into the
circuits and damage them so I would check any logic ICs directly
connected to them like U1530, U1535, and U1580.

On Thu, 31 Jan 2013 05:39:01 -0000, "Robert"
wrote:

Quick test: I tried IC U1560 in the working scope and got a trace, so it looks like some input is keeping it in blanking mode. On to more circuit analysis and tracing.

Bob


 

Are the trigger and sweep occuring? The A Gate signal signal from
schematic 6 triggers flip-flop U1535 which controls pin 15 of U1560
and should be doing something.

In chop mode, U1585 generates the chop timing which should show up at
pin 4 which blanks the CRT and pin 13 which toggles the displayed
channel. I doubt the origin of the chop timing is the problem but it
is easy to understand and check.

On Fri, 01 Feb 2013 00:42:53 -0000, "Robert"
<go_boating_fast@yahoo.com> wrote:

The difference at Pin 5 was just a front panel button. When set the same, both scopes have the same value. Although Pin 15 comes from the delayed sweep control, both scopes are set the same. Now trying to figure out how that circuit works.
Bob

--- In TekScopes@yahoogroups.com, "Robert" wrote:

Funny, as I was thinking about this while falling asleep, the thought of a stuck front panel switch came to mind, like being in single trace mode or something. It will take me some serious manual reading to figure out the switch/signal circuit effects.
Bob
--- In TekScopes@yahoogroups.com, David wrote:

I suppose that is good news since U1560 would probably be difficult to
replace. On the other hand, that just moves the problem into the
inscrutable oscilloscope logic.

I would take a close look at the horizontal and vertical mode switches
because they are subject to mechanical failure and those pullup
resistors. Those are easy to check.

Sometimes a pushbutton switch can conduct a static discharge into the
circuits and damage them so I would check any logic ICs directly
connected to them like U1530, U1535, and U1580.

On Thu, 31 Jan 2013 05:39:01 -0000, "Robert"
wrote:

Quick test: I tried IC U1560 in the working scope and got a trace, so it looks like some input is keeping it in blanking mode. On to more circuit analysis and tracing.

Bob


Robert Simpson
 

Thanks for the tip. It will help. I just bought up that part of the cicuit to look at. In fact I am just printing out the layout for note takeing.
Note, nothing on beam finder either.
Bob

--- In TekScopes@yahoogroups.com, David wrote:

Are the trigger and sweep occuring? The A Gate signal signal from
schematic 6 triggers flip-flop U1535 which controls pin 15 of U1560
and should be doing something.

In chop mode, U1585 generates the chop timing which should show up at
pin 4 which blanks the CRT and pin 13 which toggles the displayed
channel. I doubt the origin of the chop timing is the problem but it
is easy to understand and check.

On Fri, 01 Feb 2013 00:42:53 -0000, "Robert"
wrote:

The difference at Pin 5 was just a front panel button. When set the same, both scopes have the same value. Although Pin 15 comes from the delayed sweep control, both scopes are set the same. Now trying to figure out how that circuit works.
Bob

--- In TekScopes@yahoogroups.com, "Robert" wrote:

Funny, as I was thinking about this while falling asleep, the thought of a stuck front panel switch came to mind, like being in single trace mode or something. It will take me some serious manual reading to figure out the switch/signal circuit effects.
Bob
--- In TekScopes@yahoogroups.com, David wrote:

I suppose that is good news since U1560 would probably be difficult to
replace. On the other hand, that just moves the problem into the
inscrutable oscilloscope logic.

I would take a close look at the horizontal and vertical mode switches
because they are subject to mechanical failure and those pullup
resistors. Those are easy to check.

Sometimes a pushbutton switch can conduct a static discharge into the
circuits and damage them so I would check any logic ICs directly
connected to them like U1530, U1535, and U1580.

On Thu, 31 Jan 2013 05:39:01 -0000, "Robert"
wrote:

Quick test: I tried IC U1560 in the working scope and got a trace, so it looks like some input is keeping it in blanking mode. On to more circuit analysis and tracing.

Bob


 

I printed up the 475 and 485 schematics on 11x17 paper and added them
to my big 3 ring binder of test equipment I do not have a few days
ago. I sometimes scan in schematics from the paper manuals that I
have just so I can mark them up with colored pens.

At some future time, I may pick up a broken 465B or similar just so I
do not miss out on all of the fun and I have an idea for a circuit
which could replace the tunnel diodes that I would like to try.

I have lucked out with all of my oscilloscopes in not having to delve
into the ALT/CHOP/Z-Axis logic. I have however diagnosed a couple of
Tektronix universal timer/counters which involved reverse engineering
the logic circuits.

On Fri, 01 Feb 2013 02:50:47 -0000, "Robert"
<go_boating_fast@yahoo.com> wrote:

Thanks for the tip. It will help. I just bought up that part of the cicuit to look at. In fact I am just printing out the layout for note takeing.
Note, nothing on beam finder either.
Bob


Mark Wendt <mark.wendt@...>
 

Anybody found a source in the wild for this catalog?

Thanks,
Mark

On 01/30/2013 06:14 PM, Dave Daniel wrote:


Where would one find a copy of the "Tek-Made Integrated Circuits Catalog"?

Cheers,
Dave


On 1/30/2013 4:09 PM, David wrote:

The Tek-Made Integrated Circuits Catalog has details and an internal
schematic for the 155-0012-00 Z-Axis Logic IC.

Pins 5 and 15 are high impedance logic inputs so the slightly higher
voltages you measured should not damage a replacement IC but before
trying a swap, I would check the circuits that generate the voltages
going into pins 5 and 15 although I am not sure what I would look for.
There is no reason for those pins to be high.

I would also check the area around U1585.

I do not see any evidence that U1560 is bad. I suspect an earlier
problem is keeping the CRT beam blanked.