Date   

Re: Part needed for Type 576 Curve Tracer

Kurt Rosenfeld
 

Michael (and anyone else who wants to improve Tekwiki),

Email me and I will make an account for you. The email address is at the bottom of the top-level main page:

http://w140.com/tekwiki/#/media/File:Kurt_email.gif

When you're logged into the wiki, you can edit pages. Otherwise it's read-only.

-Kurt


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

On Mon, Jun 24, 2019 at 12:10 PM, Mlynch001 wrote:


On Mon, Jun 24, 2019 at 10:20 AM, Kurt Rosenfeld wrote:


Every instrument page on Tekwiki has a "Repairs" page associated with it.
The
link is near the upper left of the page. The intention is to provide a place
for people to document repairs, maintenance issue, etc.
Kurt,

I certainly can write something up and place it there as well. Just was not
sure the best or accepted method of doing this. Appreciate the instruction.

Thanks!
--
Michael Lynch
Dardanelle, AR
Kurt,

This is what I see under "Repairs" for the 576:

"576/Repairs"

"There is currently no text in this page. You can search for this page title in other pages, or search the related logs, but you do not have permission to create this page."

So How does anything get placed in that section? Because that would be a great place to have these model specific repairs documented in some sort of PDF or Other Text document.

Thanks!


--
Michael Lynch
Dardanelle, AR


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

On Mon, Jun 24, 2019 at 10:20 AM, Kurt Rosenfeld wrote:


Every instrument page on Tekwiki has a "Repairs" page associated with it. The
link is near the upper left of the page. The intention is to provide a place
for people to document repairs, maintenance issue, etc.
Kurt,

I certainly can write something up and place it there as well. Just was not sure the best or accepted method of doing this. Appreciate the instruction.

Thanks!
--
Michael Lynch
Dardanelle, AR


Re: Part needed for Type 576 Curve Tracer

Kurt Rosenfeld
 

Every instrument page on Tekwiki has a "Repairs" page associated with it. The link is near the upper left of the page. The intention is to provide a place for people to document repairs, maintenance issue, etc.


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

On Mon, Jun 24, 2019 at 08:19 AM, Glenn Little wrote:


What did Tom recommend?

Glenn

On 6/24/2019 8:56 AM, Mlynch001 wrote:
Tom,

Yes, and that is what I have done. I do not take any of the help that I
Glen,

Tom said that I definitely should share my repair. Which I thought was the right thing to do, but was not sure of using bandwidth or space for such a post. I have posted my finding above, If there is some other place to put this information, I am certainly glad to do what is needed to share my experience.

Thanks!
have received for granted! It is much appreciated. Being a novice at this, I
need all the help that I can get.

Thanks!
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


--
Michael Lynch
Dardanelle, AR


Re: Part needed for Type 576 Curve Tracer

Glenn Little
 

What did Tom recommend?

Glenn

On 6/24/2019 8:56 AM, Mlynch001 wrote:
Tom,

Yes, and that is what I have done. I do not take any of the help that I have received for granted! It is much appreciated. Being a novice at this, I need all the help that I can get.

Thanks!
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

Tom,

Yes, and that is what I have done. I do not take any of the help that I have received for granted! It is much appreciated. Being a novice at this, I need all the help that I can get.

Thanks!

--
Michael Lynch
Dardanelle, AR


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

That is an awesome way to get one of these. I feel like I almost hit the
jackpot when my Flea-Bay bid won at $255. Mine looked great and even had a
bright "spot" that showed in the pictures, so I was 95% certain that there was
a good CRT in the machine. After it arrived in ONE PIECE, I might add, First
thing I did was open the manual and started checking the power supplies. To
my relief, everything was almost spot on, EXCEPT the 5V, which was quite low
at about 3.81V. So I knew that was the first order of business, going
forward. With the power supplies mostly good and a bright controllable spot,
I knew that most of the machine was working, In addition, I was able to get
the spot to move, but could not center the spot on the screen horizontally. I
pulled all the Transistors from the display board and, by luck, the first one
that I tested (Q660) was a resistor. I replaced it with a 2N3906 and that
made it possible to center the spot, but still no trace or step generator.
After a lot of searching, I found a fellow who described symptoms almost
exactly like mine had with the 5V, so I started by looking at C759, Which was
the cause of his issue. My C759 was supposed to be 11KuF and tested at 89uF
with an ESR of something like 10 Ohms. Curiously, this cap had already
failed once before and had been replaced with a 14K uF 25V TEKTRONIX Part
with a 1992 date code. I have a hobby of "restoring" these large aluminum
caps so that the machines appear to be original. So I order the appropriate
modern cap and "Restored" this one, it looks and fits just like the original.
So I think I have this one closer to working. I fire her up and the 5V rail
has come up to about 4.1V, but still low and with a lot of current draw @ 440
mA. So I know that I have ANOTHER bad cap. More to follow.
All:

Continued from previous posts.

So, after I found that I still had issues, I started checking all the other electrolytic caps on the power supply board (several others appear to have been replaced previously). Long story short, after looking at the schematic, I landed on C789 and after carefully pulling it, I find that is was actually a big resistor, with 475 Ohms of resistance, but pretty close on capacitance. Replaced with a suitable cap and I am thinking, "I GOT this!". Not so fast, powered up and the thing STILL has low voltage, up to about 4.5V but still with excess current draw. Now I powered down and disconnect the Step generator 5V Rail @ the "Q" terminal of the step generator board (which is the only thing that uses the 5 V that I can find) and the 5 V supply pops back to an almost perfect 5.065VDC with no load! Well , I am gaining ground, but still have ANOTHER bad cap. Power down again and go back to the schematic; this time on the Step Generator board. Looking at the schematic, I find another 39uF 10V cap (C294, same as C789), another filter cap. It is difficult to access, but I am able to pull one end from the board, reconnect terminal "Q" to the step Gen board and I get a perfect 5.0VDC and about 45mV current draw. Replaced C294 with a suitable replacement (47uF 16V axial Low ESR NICHICON) and solder it into the circuit. Finally, I really think I got it! Power up, I turn up the intensity and I have 10 beautiful little points of light across the screen, indicating that the step generator is now working. I proceed to the front of the manual and start to follow the steps to check it out. Which brings me to my original post, Everything works great, except that the 1-2-5V balance is off slightly as described above. This is where I am at until i get the proper parts. I will update after more testing/repairs. I want to also take the time to thank EVERYONE on this forum who has helped me on various projects. I hope some day that I am able to help someone just a little bit, just as I have been so graciously been helped. I am always open to questions on or off the forum.

Thank You.



--
Michael Lynch
Dardanelle, AR


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

Craig,

That is an awesome way to get one of these. I feel like I almost hit the jackpot when my Flea-Bay bid won at $255. Mine looked great and even had a bright "spot" that showed in the pictures, so I was 95% certain that there was a good CRT in the machine. After it arrived in ONE PIECE, I might add, First thing I did was open the manual and started checking the power supplies. To my relief, everything was almost spot on, EXCEPT the 5V, which was quite low at about 3.81V. So I knew that was the first order of business, going forward. With the power supplies mostly good and a bright controllable spot, I knew that most of the machine was working, In addition, I was able to get the spot to move, but could not center the spot on the screen horizontally. I pulled all the Transistors from the display board and, by luck, the first one that I tested (Q660) was a resistor. I replaced it with a 2N3906 and that made it possible to center the spot, but still no trace or step generator. After a lot of searching, I found a fellow who described symptoms almost exactly like mine had with the 5V, so I started by looking at C759, Which was the cause of his issue. My C759 was supposed to be 11KuF and tested at 89uF with an ESR of something like 10 Ohms. Curiously, this cap had already failed once before and had been replaced with a 14K uF 25V TEKTRONIX Part with a 1992 date code. I have a hobby of "restoring" these large aluminum caps so that the machines appear to be original. So I order the appropriate modern cap and "Restored" this one, it looks and fits just like the original. So I think I have this one closer to working. I fire her up and the 5V rail has come up to about 4.1V, but still low and with a lot of current draw @ 440 mA. So I know that I have ANOTHER bad cap. More to follow.

--
Michael Lynch
Dardanelle, AR


Re: Part needed for Type 576 Curve Tracer

tom jobe <tomjobe@...>
 

Hello Micheal,
You have gotten quite a bit of help from the Tekscopes group on your various projects, so a nice summary of your 576 repair would seem like the proper thing to do.
The Tekscopes message archive will retain your repair summary for many years to come and help many others.
tom jobe....

On 6/23/2019 10:55 PM, Mlynch001 wrote:
All:

If anyone is interested, I would be glad to outline what I found and what was done to bring this beast back from the dead. I am so very happy to have been able to buy this wonderful machine at a price that many are charging for the Device adapters alone. There are these diamonds in the rough out there floating around and I was fortunate to be there at the right time.


Re: Part needed for Type 576 Curve Tracer

JJ
 

Michael, Congratulations on your 576 fix. I own one myself (purchased 15 yrs ago) and used one back in engineering school some 50 years ago. Great machine - mine still works perfectly! Please, I'd be interested in learning about your findings!

Best,
John Justin


Re: Part needed for Type 576 Curve Tracer

Craig Sawyers <c.sawyers@...>
 

I am so very happy to have been able to buy this wonderful machine at a price
that many are charging for the Device adapters alone.
Michael Lynch
Dardanelle, AR
I can beat that. I paid precisely nothing for mine, or for a spares unit that is just missing the CRT.

Mind you, before I got the spares unit, I had to rewind the HT transformer in the free one to
resurrect it....

Craig


Re: Part needed for Type 576 Curve Tracer

Mlynch001
 

All:

If anyone is interested, I would be glad to outline what I found and what was done to bring this beast back from the dead. I am so very happy to have been able to buy this wonderful machine at a price that many are charging for the Device adapters alone. There are these diamonds in the rough out there floating around and I was fortunate to be there at the right time.

--
Michael Lynch
Dardanelle, AR


Re: TDS520B - the screen gradually expands and then darkens in about 20 mins

unclebanjoman
 

Thank you, e-mail received.

Max


Re: 577 step amplifier

DW
 


Re: 577 step amplifier

DW
 


Re: TDS520B - the screen gradually expands and then darkens in about 20 mins

nonIonizing EMF
 

On Sun, Jun 23, 2019 at 01:51 PM, unclebanjoman wrote:


Please note that I'm from Italy, near Venice.
I sent a direct email message regarding a unit I was going to purchase though shipping was too much for me to ship to the U.S.

Maybe you or someone over there can use. If anyone else is interested... feel free to reply.

Kindest Regards


Re: 577 step amplifier

DW
 

I probed the horizont alamplifier U530 pin 6 and it appears slightly noisey, with the step generator on it becomes even more noisey. When I adjust the offset multi on the step generator this causes very noticeable spikes on the output of U530. I tried to probe the input of U530 but the oscilloscope I am using currently is not sensitive enough with a 10X probe.

I will locate the 1X probe for more sensitivity and include pictures soon.


Re: TDS520B - the screen gradually expands and then darkens in about 20 mins

unclebanjoman
 

O.K. Sthepen, thank you.

Please note that I'm from Italy, near Venice.

Max


Re: 2467B Focus and A5 issues

satbeginner
 

On Sun, Jun 23, 2019 at 08:29 PM, Chuck Harris wrote:


It is getting to the
point where there are way more 2465B's than there are
salvageable A5 boards. Dead A5 boards are what supplies all
of the used parts that the various groups in Greece and Israel
sell.
Hello Chuck and others,

I love a dead A5 SMD board, maybe not easy to fix, and maybe not good looking when fixed, but hey: when repaired and it works, why not??

Again, more pictures here: https://groups.io/g/TekScopes/album?id=92199

yet another step in the right direction :-)

The calibration issue was caused by yet another eaten away resistor, this time in the "B Tim Ref" , R2430 was open.
This caused both losing the DC level being responsible for the default Timebase speed, for the and a way too low Var setting when used.

So, another flying resistor added, and now the delayed timebase was near the wanted value, so the calibration did work this time.

So, the last two pictures are taken after the calibration, both Cal-8, Cal-1 and Cal-2, not bad for a scope that was sold as not working two days ago :-)

Now the delayed timebase is working as designed, a 1uS pulse is now shown as 5 division 200nS/div pulse :-)

Again, the A5 board is not very good looking anymore, but it does work, and that is what count, doesn't it?.

So, if there are "non repairable" SMD based A5 boards near Spain, let me know, I would love to dig in.

Un saludo,

Leo

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