Hi Chuck,
I joined earlier today. The problem with Logic Analyzers is extremely rapid obsolescence, sky high cost, a steep learning curve, and very limited usefulness beyond solving the specific job you buy them for.

After they serve the purpose they were bought for they end up in a box somewhere which eventually gets thrown out.

Dennis Tillman W7PF

Gary;

Yes I understand that an open resistor can lead to other problems. Of course it has already been operated that way while I was troubleshooting other areas of the unit. Apparently nothing else that I can determine at this time was damaged - no fuses or other parts have been found to be burned etc.

I will admit that I did not discover the burned resistor right away. I had done a fairly detailed visual inspection in the early stages of troubleshooting, but it turned out that when this resistor burned open the color band that indicated the value 6 had changed color to appear orange and I thought I was looking at a 1.3K ohm resistor. The body color (light brown) had changed so little that I did not notice it. It just goes to show how easy it is to misinterpret something while examining a piece of gear.

Thanks for responding!

Joe
KC5LY

Hi Dennis,

I co moderate a yahoo group called:

Tektronix-Logic-Analyzers

It hasn't caught fire just yet, but it has promise.

-Chuck Harris

'Dennis Tillman' dennis@ridesoft.com [TekScopes] wrote:

Thanks Bert. Is there a way to fix it? -Barry

On Dec 24, 2014 11:57 AM, "Bert Haskins bhaskins@chartermi.net [TekScopes]"
<TekScopes@yahoogroups.com> wrote:

Looks like the sweep is out of sync with the staircase generator.
I see that all the time on one of my CTs.

On 12/24/2014 12:47 PM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] wrote:

Looks like power supply ripple. Have you checked the supplies yet?

Tom

----- Original Message -----
From: fretsbiz@gmail.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Wednesday, December 24, 2014 12:36 PM
Subject: RE: [TekScopes] 575 curve tracer problem

Thanks Dennis....apparently that link is for mobile devices. Here's
the URL for PCs:

Tektronix 575 Curve Tracer CRT Glitches
https://www.youtube.com/watch?v=QzByjLXnvls

https://www.youtube.com/watch?v=QzByjLXnvls

Tektronix 575 Curve Tracer CRT Glitches
https://www.youtube.com/watch?v=QzByjLXnvls I'm trying to figure out
what is causing these glitches on my 575. If you have experience with
solving this issue....please share!

View on www.youtube.com https://www.youtube.com/watch?v=QzByjLXnvls
Preview by Yahoo

------------------------------------

------------------------------------


------------------------------------

Yahoo Groups Links

Tom, I checked the ripple and everything I saw was within spec.
However....now that I think about it....I didn't check ripple while there
was a FET under loaf in the test panel. I'll redo that one today. Thanks,
-Barry

On Dec 24, 2014 11:44 AM, "'Tom Miller' tmiller11147@verizon.net
[TekScopes]" <TekScopes@yahoogroups.com> wrote:

Looks like power supply ripple. Have you checked the supplies yet?

Tom


----- Original Message -----
From: fretsbiz@gmail.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Wednesday, December 24, 2014 12:36 PM
Subject: RE: [TekScopes] 575 curve tracer problem

Thanks Dennis....apparently that link is for mobile devices. Here's the

URL for PCs:

Tektronix 575 Curve Tracer CRT Glitches

https://www.youtube.com/watch?v=QzByjLXnvls

https://www.youtube.com/watch?v=QzByjLXnvls

Tektronix 575 Curve Tracer CRT Glitches

https://www.youtube.com/watch?v=QzByjLXnvls I'm trying to figure out what
is causing these glitches on my 575. If you have experience with solving
this issue....please share!

View on www.youtube.com https://www.youtube.com/watch?v=QzByjLXnvls
Preview by Yahoo

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Normaly both comes from the mains frequency ( 50 / 60 Hz ) with 100/120
or 200/240 steps !

Herbert


Am 24.12.2014 17:57, schrieb Bert Haskins bhaskins@chartermi.net
[TekScopes]:

Looks like the sweep is out of sync with the staircase generator.
I see that all the time on one of my CTs.

On 12/24/2014 12:47 PM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] wrote:

Looks like power supply ripple. Have you checked the supplies yet?

Tom

----- Original Message -----
From: fretsbiz@gmail.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Wednesday, December 24, 2014 12:36 PM
Subject: RE: [TekScopes] 575 curve tracer problem

Thanks Dennis....apparently that link is for mobile devices. Here's
the URL for PCs:

Tektronix 575 Curve Tracer CRT Glitches
https://www.youtube.com/watch?v=QzByjLXnvls

https://www.youtube.com/watch?v=QzByjLXnvls

Tektronix 575 Curve Tracer CRT Glitches
https://www.youtube.com/watch?v=QzByjLXnvls I'm trying to figure out
what is causing these glitches on my 575. If you have experience with
solving this issue....please share!

View on www.youtube.com https://www.youtube.com/watch?v=QzByjLXnvls
Preview by Yahoo

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Looks like power supply ripple. Have you checked the supplies yet?

Tom

What glitches are you talking of ????

For me, that looks pretty GOOD !

Herbert


Am 24.12.2014 17:36, schrieb fretsbiz@gmail.com [TekScopes]:

Thanks Dennis....apparently that link is for mobile devices. Here's the URL for PCs:


Tektronix 575 Curve Tracer CRT Glitches https://www.youtube.com/watch?v=QzByjLXnvls



https://www.youtube.com/watch?v=QzByjLXnvls

Tektronix 575 Curve Tracer CRT Glitches https://www.youtube.com/watch?v=QzByjLXnvls I'm trying to figure out what is causing these glitches on my 575. If you have experience with solving this issue....please share!



View on www.youtube.com https://www.youtube.com/watch?v=QzByjLXnvls
Preview by Yahoo

I think Tektronix was just being paranoid. The diodes they used have a reverse
leakage specification of 10 picoamps maximum which is low enough not to require
balancing. Maybe they were operating in a high temperature environment though
which would raise the leakage considerably.

The suggested BAV199 dual diode has a rather poor specification of 5 nanoamps
maximum which would yield 5 millivolts of offset. Its typical leakage is 3
picoamps so this probably represents a testing issue; testing for low leakage is
time consuming which adds significantly to the cost of a part.

In practice with JFET protection circuits like this, diode leakage can be low
enough that only one is needed but you need a diode which actually has low
leakage. A JFET with drain and source wired together makes a good guaranteed
low leakage diode. So does the collector-base or emitter-base junction of many
small signal bipolar transistors but unlike a JFET, they need to be tested to
verify low leakage.

For repair of this 1A4, I would use the collector-base junctions of 2N3904
transistors. They typically have leakage under 10 picoamps but they need to be
tested which is easy enough with a good 10 megohm input voltmeter.

The Tek scopes discussion, sure.

The off topic comments and quotes, I am not so sure about.
They are divisive however well meaning and carefully put they are.

I'm as guilty as the next guy in that regard, so I'll shut up now.

ST

On Wed, Dec 24, 2014 at 5:50 PM, Jim Popwell jpopwell@cstel.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:

it’s nice to be part of something like this….

jim

Barry,
That link doesn't go to your 575 video.
Instead it goes to a page with 100+ unrelated videos on it as near as I can
tell.
Chrome and IE11 took me to the same place.
Dennis Tillman W7PF

Hey guys, can anyone tell me what is causing my 575 to act this way and how to fix it? Here's a YouTube video of the problem:


www.YouTube.com/?#/watch?v=QzByjLXnvls

Thanks,
-Barry

Hi Bruce,
Thanks for the link. It is a very small group and almost inactive. I have my
fingers crossed they can give me a few leads.
Dennis Tillman W7PF

it’s nice to be part of something like this….

jim

On Dec 24, 2014, at 7:49 AM, Ken Chalfant kpchalfant@msn.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

Greetings,

For the Christian world, and at least the secular American community, today is Christmas eve. For a great many people across the globe today is just December 24th.

2014 has not been an easy year for this planet or the human race. I tend to believe that governments, religions, and multinational corporations are hurting us more than helping us. Unfortunately the struggle between races, suspicion of authority - especially the militarized police in the USA - unrest across America and the struggles of the world at large challenge our beliefs and our confidence in mankind.

But we can give pause and think about our the HP and Tektronix groups of which we are members. We are bound together by common interests. By way of email addresses and language structure it is obvious we are spread across the face of the earth. When someone asks a question, needs some help, or a near unobtainable part, no one ever asks about race, religion, or political affiliation - we just help.

We are a model for successful human relations.

I suspect most, if not all of us, carry this "willingness to help" into our daily lives.

I realize that "in person" it is sometimes harder. So many ingrained prejudices and fears can cause us to be cautious, nervous, even unwilling, and sometimes that proves to be wise. Yet here we put all of that aside. We are often unaware of our differences and don't care. We just care about helping each other.

We have created a working model of human interaction and with a little effort we can, and probably do, carry this thinking with us everywhere we go.

So - thank each and every one of us for the help, wisdom, and kindness we share throughout the years.

If you embrace Christ I wish you the warmth of your faith. If you simply love the Christmas season I wish you a very merry Christmas.

If you are of a different faith, or none at all, and no matter where in the world you call home, what flag you live under, the language you speak, or the color of your skin - I wish you peace and happiness.

My hope for us all is that 2015 will be a better year than was 2014.

Perhaps if each of us carries the friendliness and spirit of cooperation that we share in these groups into our daily lives just a little more intensely in 2015 we can make the whole world a little bit better.

I wish all of you a safe, successful, and prosperous 2015.

Warm regards,

Ken (USA)

[Non-text portions of this message have been removed]

+100

"I feel sorry for people who don't drink. When they
wake up in the morning, that's as good as they're
going to feel all day. "
~Frank Sinatra

There is a Tektronix Logic Analyzers Group at https://groups.yahoo.com/neo/groups/Tektronix-Logic-Analyzers/conversations/messages

Bruce

Joe:

Be very careful about opening resistors. Often, the resistor is part of a
divider chain and it sets the output of a voltage power source. Opening the
resistor can send the voltage source to catastrophic levels and cause
severe damage to entire driven circuits.

Gary
On Dec 24, 2014 8:16 AM, "strijw426@yahoo.com [TekScopes]" <
TekScopes@yahoogroups.com> wrote:

Not having received any suggestions, here is what I propose to do for now:
I will replace R113, the 1.6K ohm 1/4W 5% carbon film resistor with a new
one (ordered a set of them).
I have ordered a replacement for Q114, a 2N5451, and Q115, a 2N5551 in
case I need to replace those.

I will install R113 first and reconnect everything and install the board
on the chassis. I will apply power and see if R113 burns again. It is
possible that I might have caused the burned resistor because at one point
I had one interconnect cable plugged in 1 position off.

If R113 holds, I can then take some AC and DC voltage measurements on the
Vertical & High Voltage board to see where that leads.

If R113 burns again, I will open the resistor and measure other voltages
on the board to see if that produces any other indications of trouble.

Joe
KC5LY

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Not having received any suggestions, here is what I propose to do for now:
I will replace R113, the 1.6K ohm 1/4W 5% carbon film resistor with a new one (ordered a set of them).
I have ordered a replacement for Q114, a 2N5451, and Q115, a 2N5551 in case I need to replace those.

I will install R113 first and reconnect everything and install the board on the chassis. I will apply power and see if R113 burns again. It is possible that I might have caused the burned resistor because at one point I had one interconnect cable plugged in 1 position off.

If R113 holds, I can then take some AC and DC voltage measurements on the Vertical & High Voltage board to see where that leads.

If R113 burns again, I will open the resistor and measure other voltages on the board to see if that produces any other indications of trouble.

Joe
KC5LY