Topics

577 Curve Tracer question

Jason A.
 

Hello all! I've recently acquired a 577D1 curve tracer that was missing a few components. I managed to find everything online that it was missing (at least at first blush - time will tell on my observation skills and glasses prescription). Replacement parts 156-0200-00 for U520 and U530 arrived yesterday. Before I plug in two somewhat hard to find parts, is there anything I should be checking first?

 

Hi Jason,
Congratulations. You've got yourself a great curve tracer. If you ever get the need to test vacuum tubes I designed an inexpensive adapter that will let you do that on a 577. I wrote a paper on how I did it.

In my experience the only thing you will probably need to adjust is the storage. My impression of all Tek storage tubes is that they are particularly sensitive to their voltages being properly set. There is a procedure in the Service Manual for doing this. I found it so confusing (many of the adjustments seem to interact with each other) that I eventually gave up and just settled for something that I could live with. After a few minutes the scope has warmed up it the adjustments I made seem to make the storage work OK. I'm sure that someone else could do a better job than I did.

What part of the circuit are U520 and U530 used for? It seems odd that they were missing. Do you have any idea why?

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jason A. via Groups.Io
Sent: Wednesday, January 08, 2020 8:24 AM
To: TekScopes@groups.io
Subject: [TekScopes] 577 Curve Tracer question

Hello all! I've recently acquired a 577D1 curve tracer that was missing a few components. I managed to find everything online that it was missing (at least at first blush - time will tell on my observation skills and glasses prescription). Replacement parts 156-0200-00 for U520 and U530 arrived yesterday. Before I plug in two somewhat hard to find parts, is there anything I should be checking first?




--
Dennis Tillman W7PF
TekScopes Moderator

Jason A.
 

Hi Dennis,

I am a very happy user of your adapter on a 7CT1N! :-) I got the 577 for $125+shipping (still can't believe it, but there may be a reason...) mainly for the additional voltage and current ranges the 577 offers.

The U520 and U530 are on the main board for the 577 as Op Amps showing in the -Horizontal circuit, it appears as drivers to the display board. Their rails are listed to be +/-12v.

I also have a K436, Q1392 and Q310 on the way. Those were the components that were obviously missing. I'm hoping this doesn't turn into a months long repair ordeal, but who knows. It should be worth it in the end if my skills match my ambition.

Thank you and best regards,

Jason

David Berlind
 

Hi Dennis.

I have my 577 and my Eico 667 Tube tester ready for the marriage according
to your paper. It's in my project queue and I'm looking forward to the
undertaking. First, I'm going to bring the tube tester up to snuff. Do you
have a shortlist of things to do in order to get the storage into a good
place on the 577 (rather than reading the confusing manual)?

Thanks.

David

On Wed, Jan 8, 2020 at 1:18 PM Dennis Tillman W7PF <@Dennis_Tillman_W7PF>
wrote:

Hi Jason,
Congratulations. You've got yourself a great curve tracer. If you ever get
the need to test vacuum tubes I designed an inexpensive adapter that will
let you do that on a 577. I wrote a paper on how I did it.

In my experience the only thing you will probably need to adjust is the
storage. My impression of all Tek storage tubes is that they are
particularly sensitive to their voltages being properly set. There is a
procedure in the Service Manual for doing this. I found it so confusing
(many of the adjustments seem to interact with each other) that I
eventually gave up and just settled for something that I could live with.
After a few minutes the scope has warmed up it the adjustments I made seem
to make the storage work OK. I'm sure that someone else could do a better
job than I did.

What part of the circuit are U520 and U530 used for? It seems odd that
they were missing. Do you have any idea why?

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jason
A. via Groups.Io
Sent: Wednesday, January 08, 2020 8:24 AM
To: TekScopes@groups.io
Subject: [TekScopes] 577 Curve Tracer question

Hello all! I've recently acquired a 577D1 curve tracer that was missing a
few components. I managed to find everything online that it was missing
(at least at first blush - time will tell on my observation skills and
glasses prescription). Replacement parts 156-0200-00 for U520 and U530
arrived yesterday. Before I plug in two somewhat hard to find parts, is
there anything I should be checking first?




--
Dennis Tillman W7PF
TekScopes Moderator



 

Hi David,
I'm not very good when it comes to following directions or asking others for help when I don't understand something so part of the fault is with me. I suggest you give the directions a try and form your own conclusion. I will be better off if others have greater success than me because then I can ask them for their help. As it is you are asking a blind person to lead you. How smart is that?

After I grew frustrated with the adjustment instructions in the service manual I just started turning trim pots until things seemed "better" than they were before I opened up the curve tracer. At that point I thought to myself you should stop because it is almost certain that you can only make it worse if you don't stop.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David Berlind
Sent: Wednesday, January 08, 2020 12:33 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 577 Curve Tracer question

Hi Dennis.

I have my 577 and my Eico 667 Tube tester ready for the marriage according to your paper. It's in my project queue and I'm looking forward to the undertaking. First, I'm going to bring the tube tester up to snuff. Do you have a shortlist of things to do in order to get the storage into a good place on the 577 (rather than reading the confusing manual)?

Thanks.

David

On Wed, Jan 8, 2020 at 1:18 PM Dennis Tillman W7PF <@Dennis_Tillman_W7PF>
wrote:

Hi Jason,
Congratulations. You've got yourself a great curve tracer. If you ever
get the need to test vacuum tubes I designed an inexpensive adapter
that will let you do that on a 577. I wrote a paper on how I did it.

In my experience the only thing you will probably need to adjust is
the storage. My impression of all Tek storage tubes is that they are
particularly sensitive to their voltages being properly set. There is
a procedure in the Service Manual for doing this. I found it so
confusing (many of the adjustments seem to interact with each other)
that I eventually gave up and just settled for something that I could live with.
After a few minutes the scope has warmed up it the adjustments I made
seem to make the storage work OK. I'm sure that someone else could do
a better job than I did.

What part of the circuit are U520 and U530 used for? It seems odd that
they were missing. Do you have any idea why?

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Jason A. via Groups.Io
Sent: Wednesday, January 08, 2020 8:24 AM
To: TekScopes@groups.io
Subject: [TekScopes] 577 Curve Tracer question

Hello all! I've recently acquired a 577D1 curve tracer that was
missing a few components. I managed to find everything online that it
was missing (at least at first blush - time will tell on my
observation skills and glasses prescription). Replacement parts
156-0200-00 for U520 and U530 arrived yesterday. Before I plug in two
somewhat hard to find parts, is there anything I should be checking first?

Dennis Tillman W7PF
TekScopes Moderator



--
Dennis Tillman W7PF
TekScopes Moderator

Jason A.
 

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason

Jason A.
 

A couple clarifications...

I haven't done my 577 yet (still waiting on a couple parts), but I assume the storage on it is similar to the 5111.

Adjusting the storage in no way takes a week. But it will take you a couple hours if you follow 0-6... and about step 6... When I have done storage adjustments on my other equipment, I have always gone "By the book" on step 5 and then step 6 is going back through the procedure a 2nd time applying lessons I learned from the first pass. I also made notes at the end on where the test point voltages were at the end of the adjustment process and took the post-it note and applied it to my manual page where the procedure is. That way if you find things not working very well a few weeks out, you can quickly check the voltages you last saw when everything was working for you and this can help track down any issues you may run into with old trimmers.

 

Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason




--
Dennis Tillman W7PF
TekScopes Moderator

 

Hi Jason,

I think it is virtually certain that Tek used the entire top half of the 5111 for the 577D1 since the 5111 is the only 5000 series scope with split-screen storage. That would mean the schematics and adjustment procedures would be identical.

Dennis Tillman W7PF

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 10:09 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

A couple clarifications...

I haven't done my 577 yet (still waiting on a couple parts), but I assume the storage on it is similar to the 5111.

Adjusting the storage in no way takes a week. But it will take you a couple hours if you follow 0-6... and about step 6... When I have done storage adjustments on my other equipment, I have always gone "By the book" on step 5 and then step 6 is going back through the procedure a 2nd time applying lessons I learned from the first pass. I also made notes at the end on where the test point voltages were at the end of the adjustment process and took the post-it note and applied it to my manual page where the procedure is. That way if you find things not working very well a few weeks out, you can quickly check the voltages you last saw when everything was working for you and this can help track down any issues you may run into with old trimmers.




--
Dennis Tillman W7PF
TekScopes Moderator

Ken Eckert
 

Hello;

I remember my first area in a military cal lab after my PMEL training was
the scope bench. At the time the Canadian military had a huge number of Tek
545A scopes for the Pinetree radar line.

A 10 min explanation of the adjustment procedure and I was turned loose....
4 days later had recovered from my misadjustment and adjusted my first
delay line..much to the amusement of the senior techs.

Baptism by tuning wand!

Ken

On Friday, January 10, 2020, Dennis Tillman W7PF <@Dennis_Tillman_W7PF>
wrote:

Hi Jason,
You are not alone. Now that you mention your experience adjusting the
distributed amplifier delay line I am reminded that engineering school
graduates who were interviewing at Tek (who we shall call the 'victims")
were often introduced to the (mostly) women in the department that adjusted
the delay line amplifier for a flat response. Of course they could do it
quickly because they learned by repetition how each adjustment affected the
response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to
tune it for a flat response. After about 30 minutes the interviewer came
back to check the "victims" progress. I haven't heard that anyone ever
passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some
tubes in my 535A - the Delay Line is another one of those adjustments. By
the time I was done messing with it about a week later, I came to the
conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some
tubes in my 535A - the Delay Line is another one of those adjustments. By
the time I was done messing with it about a week later, I came to the
conclusion "I don't ever want to do that again.. But at least if there is
a next time, I know what I'm in for." I have had a similar experience
adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting
the storage is no worse than the delay line in a 535A. That said, it's not
much less frustrating either. I would agree with Dennis on this one and
would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a
good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make
before beginning.

2 - When you think you have a good understanding, read through it again,
locating the adjustment points and test points and go through a "dry run,"
just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before
you start changing things so you know you can at least get back to where
you started from. The same goes for the voltage test points - write down
what the voltages were before you started so you can hopefully end back up
there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of
a turn back and forth once or twice from where you think they should be to
see the effect of each one, and to make sure there's no dust or anything
else in the trimmer that will make things jump around on you later. (Note
1: I noticed this more with 500 series scopes and the older equipment, and
it's probably more due to the age of the trimmers/potentiometers having
time to oxidize or collect pollution. Note 2: some trimmers have a small
useful life of turns, so don't go crazy winding them back and forth dozens
of times or you may put a lot of wear out the wiper contact or resistance
strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject
altogether. Hopefully you won't need to clean them, but if you do, make
sure you look carefully in the manual and near the adjustment points to
make sure there isn't any advice on cleaning things. Some Tektronix parts
have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the
2nd time through the adjustment process and chances are you'll be pretty
darned close at the end.

Best of luck and best regards,

Jason




--
Dennis Tillman W7PF
TekScopes Moderator



Mlynch001
 

On Fri, Jan 10, 2020 at 12:49 PM, Dennis Tillman W7PF wrote:


Hi Jason,

I think it is virtually certain that Tek used the entire top half of the 5111
for the 577D1 since the 5111 is the only 5000 series scope with split-screen
storage. That would mean the schematics and adjustment procedures would be
identical.

Dennis Tillman W7PF
Dennis,

You are correct. I took the top off a 5111 and replaced the display on a 577D2, turning it into a D1. It does have a non-functional Calibration loop on the front panel. Internally, there were a few wires that had to be swapped, in the harness but otherwise it was a straightforward conversion.

--
Michael Lynch
Dardanelle, AR

Harvey White
 

One trick I heard of was to touch the adjustment with a screwdriver.  If it affected the place you wanted to change, then adjusting it was a good idea.  If not, then don't bother with it.

Harvey

On 1/10/2020 1:24 PM, Dennis Tillman W7PF wrote:
Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason



Dave Daniel
 

Conductive or non-conductive screwdriver? A conductive screwdriver will couple body capacitance to the pot, while a non-conductive screwdriver will not, but may apply a static charge to the pot unless it is discharged first.

DaveD

Sent from a small flat thingy

On Jan 10, 2020, at 20:52, Harvey White <madyn@...> wrote:

One trick I heard of was to touch the adjustment with a screwdriver. If it affected the place you wanted to change, then adjusting it was a good idea. If not, then don't bother with it.

Harvey


On 1/10/2020 1:24 PM, Dennis Tillman W7PF wrote:
Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason





Harvey White
 

excellent point, and I'll have to guess.  It's one with a small brass tip, but not completely conductive.  As you note, completely nonconductive would be anticipated to have no effect.

I'm not thinking pots here, but the variable capacitors in the delay line.  Having mentioned that, it would likely be whatever tek mentioned to adjust the line itself, but I'm guessing.

Harvey

On 1/10/2020 9:06 PM, Dave Daniel wrote:
Conductive or non-conductive screwdriver? A conductive screwdriver will couple body capacitance to the pot, while a non-conductive screwdriver will not, but may apply a static charge to the pot unless it is discharged first.

DaveD

Sent from a small flat thingy

On Jan 10, 2020, at 20:52, Harvey White <madyn@...> wrote:

One trick I heard of was to touch the adjustment with a screwdriver. If it affected the place you wanted to change, then adjusting it was a good idea. If not, then don't bother with it.

Harvey


On 1/10/2020 1:24 PM, Dennis Tillman W7PF wrote:
Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason




Chuck Harris
 

When I am doing transient response on distributed amplifiers,
I touch various points and adjustment caps in the circuit with
a stick that has a small strip of metal on its end... something
1/16" x 1/4" works for me.

The metal adds a little capacitance to the node being touched,
and the result will show up on the scope screen where that node's
greatest affect will occur... like a little built in TDR.

If you can't see any change, or the screen goes all wonky, you
need to change the size of the metal on the probe.

-Chuck Harris

Harvey White wrote:

excellent point, and I'll have to guess. It's one with a small brass tip, but not
completely conductive. As you note, completely nonconductive would be anticipated to
have no effect.

I'm not thinking pots here, but the variable capacitors in the delay line. Having
mentioned that, it would likely be whatever tek mentioned to adjust the line itself,
but I'm guessing.

Harvey


On 1/10/2020 9:06 PM, Dave Daniel wrote:
Conductive or non-conductive screwdriver? A conductive screwdriver will couple body
capacitance to the pot, while a non-conductive screwdriver will not, but may apply
a static charge to the pot unless it is discharged first.

DaveD