Date   

Re: 576 Curve Tracer HV Transformer Rebuild

Chuck Harris <cfharris@...>
 

That's easy. Some call it the teacup method. Put the core into
a pot of water and boil. Though I usually just put it into my
environmental chamber and heat it to 140C. The epoxy turns to
something like chewing gum while it is hot.

-Chuck Harris

Gordon wrote:

On 18/05/2013 21:05, Chuck Harris wrote:
At this point in time... and probably for the rest of time... no
one makes EE cores that have square outer legs, and a round center
leg.
Any tips on getting cores apart? I might have to do one some time soon.

Cheers


Re: 576 Curve Tracer HV Transformer Rebuild

Gordon <tekscopes@...>
 

On 18/05/2013 21:05, Chuck Harris wrote:
At this point in time... and probably for the rest of time... no
one makes EE cores that have square outer legs, and a round center
leg.
Any tips on getting cores apart? I might have to do one some time soon.

Cheers


Re: 2465B Source code..

macgregor54 <fauxscot@...>
 

thanks, lazystrings...

(turns out my new acquaintance is already a member here. this suggests to me that this isn't the best route to locate the SC, but it's my first stop usually on any tek quest.)

your idea is a good one, and i've employed it before. tedious, but it works.

this is also wonderful logic analyzer territory. in conjunction with the cal program, monitoring the NVRAM chip for write activity when any cal factor is committed should show the selected addresses and data. It's not likely that after bootup of the scope that the NVRAM is accessed that much, so writes to it would be infrequent unless you were calibrating. it would take 24 channels and some clock inputs or qualifiers, but that's exactly the kind of thing that logic analyzers are for. they're pretty cheap these days, too, and only a slow one is needed for something like a 6802. so that's a solution, too and not quite so tedious.

thanks for the input!

are any old tek employees from the scope division on the board from the 2465 era that you know of? i haven't been on the group for a long time (everything i have sort of works for the moment.)

--- In TekScopes@yahoogroups.com, "lazystrings" <casinada@...> wrote:

You can probably find that using an Eprom programmer reading the contents of the DS1225Y and then go to the calibration routines but perform each CAL individually and see what changes in memory. I don't know if is possible to read the contents of the RAM using the GPIB if you have the option. Lots of things are stored in that RAM and they change each time you turn the Scope on.
You can also read the contents of the Eprom U2360 on the A5 board and disassemble the code. I think that the processor U2140 is a 68A02. That could be a fun project :)

--- In TekScopes@yahoogroups.com, "macgregor54" <fauxscot@> wrote:

Hi folks....

I made an acquaintance from across the pond who is looking to hack his 2465B cal setting so as to avoid having to do the entire calibration routine.

i have managed to obtain actual source code for 2600 series personal Fourier analyzers and I was wondering if anyone here has it for the 2465b? I know it's a long shot, but I managed to get the 2600 code after a multi-year search once i found some principal engineers, and i was hoping to find someone here who perhaps worked on the product line, or who had a map of the cal NVRAM contents.

What say you, wizards of Tek-ness? Any 2465B gurus, former Tekkies, gifted hackers, etc. in the group? I think this is one of their abandoned products, and it would unlikely involve any copyright issues, if that's a concern.

All leads much appreciated.


Re: 576 Curve Tracer HV Transformer Rebuild

Chuck Harris <cfharris@...>
 

Hi Michael,

I can't say that I have ever met Bill, but like anyone winding
transformers for old tek scopes, he would have had to rely on used
cores, because when TDK bought the Allen-Bradley magnetics group,
they shut it down.

At this point in time... and probably for the rest of time... no
one makes EE cores that have square outer legs, and a round center
leg.

-Chuck Harris



Michael A. Terrell wrote:


-----Original Message-----
From: Chuck Harris <cfharris@erols.com> Sent: May 18, 2013 8:42 AM To:
TekScopes@yahoogroups.com Subject: Re: [TekScopes] 576 Curve Tracer HV
Transformer Rebuild

I'm working on it... but life keeps intervening.

Bill Schell retired from winding about 10 years ago. Proof that he is way
smarter than me!

Is/was he a pilot? 20 + years ago a guy was haunting the asset recovery business
I worked for, digging through the piles of SMPS boards and anything that had
ferrite cores to rewind a Tektronix scope transformer.


The whole winding business seems like it should be profitable, but in reality
there are about 2 hours in each transformer... and we live in a world where the
scopes aren't worth 2 hours billed at any member of the group's labor rate.

So, I will finish my winder when I can steal enough time from the work that pays
the bills...

Some of us have long run out of billable hours. :(

Michael A. Terrell


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

Yahoo! Groups Links


Re: Tek 24XX parts Mule Complete and Cheap!

David DiGiacomo
 

On Sat, May 18, 2013 at 12:46 PM, leev_98 <leevogt@cox.net> wrote:
FYI:
Hope this helps some one:

http://www.ebay.com/itm/TEK-2445B-Oscilloscope-200-MHz-4-Channel-/261216294316

The top cover itself is worth this price.
It's an auction, with 4 days left to go, for a scope being sold as
working, with right of return. It will go for market price.


7904A trigger board latest

Craig Sawyers <c.sawyers@...>
 

So the inputs that come from the vertical compartment trigger output
followers go via four power splitters on the trigger board - each three 50
ohm resistors in a triangle. Checking the resistances - 25 ohms, 25 ohms,
25 ohms, 33 ohms. Say what? Now the nice thing about hypcon packaged
hybrids is that you can probe the tracks on the top of the hybrid.
Basically one input was not connecting to the hybrid.

Turns out the circuit board pads were tarnished. Now these are gold plated,
but over time underlying metals (adhesion, usually chrome or nickel) leach
to the surface, oxidise and make a high resistance contact. Possibly
because of storage conditions, humidity etc, or the plating being flakey in
the first place.

Aha! So each hybrid came off, the circuit card pads were polished and then
cleaned with Caig Pro-Gold, and the hybrids reinstalled. Then I checked all
connections to all 5 hybrids by probing the hybrid tracks and checking
continuity to whatever they connect to - all absolutely perfect.

And that made precisely zero change!!! Diff outputs of trigger B still at
-0.7V!

So I am just setting up to run the board from bench supplies - +/-15V and
+5V. I am going to get to the bottom of this darned conundrum if it kills
me.

Craig


Re: Rant: Analog vs Digital

Brad Thompson <brad.thompson@...>
 

On 5/17/2013 10:37 PM, Derward Myrick wrote:
<snip>
*From:* Peter Gottlieb <mailto:hpnpilot@verizon.net>
*To:* TekScopes@yahoogroups.com <mailto:TekScopes@yahoogroups.com>
*Sent:* Friday, May 17, 2013 6:45 PM
*Subject:* Re: [TekScopes] Re: Rant: Analog vs Digital

As a kid I knew someone who worked there. He had gotten several
patents for them from projects he created from parts he
brought home. These days most companies would instead fire
you and have you arrested for theft.
Those stolen parts don't help them this quarter, you know.

On 5/17/2013 2:54 PM, Derward Myrick wrote:
>
> Brad, back in the 1960s I know that at Bell Labs all I had to do
for parts to build anything was go to the supply and get a cart
and load it up. All you had to do was sign-out what you got so they
could reorder it. That is why Bell Labs had so many patents.
They did not restrain you on using parts at home. This is how
a REAL progressive company worked. I was working on the Nike Zeus System.

Hello, Derward and the group--

A couple of years ago, I was able to rescue hundreds of pounds of mixed
electronic components and apportion them out to interested amateur-radio
operators who still build electronics:

http://www.tmworld.com/design/characterization/4388107/A-few-pounds-of-parts

I hoped (in vain) that we'd received a "come and get it" call from
an electronics business that was about to scrap a stockroom, but to
date it hasn't happened<g>.

73--

Brad AA1IP

P.S.: Test & Measurement World no longer publishes a print edition,
so if anyone would like to contact me, write me at my "from" address.


Tek 24XX parts Mule Complete and Cheap!

 


Re: TDS540 problems

alberto.vaudagna
 

And why DS1250 seem wired?

--- In TekScopes@yahoogroups.com, "jayw_comark" <jayw_comark@...> wrote:

The DS1250 looks a bit weird with the circle pattern on the top, but I don't think that's a problem (for now)

If you try to power up with with ribbon cable to the CRT assembly disconnected, does it power on then?

Have you checked for shorts on the power rails?

When you try to power on, does it briefly try then shut down?

After it's been off for awhile with the power cord disconnected, when you plug it in and toggle the rear switch to on, does it emit a little ticking sound once?

Jay

--- In TekScopes@yahoogroups.com, "alberto.vaudagna" <alberto.vaudagna@> wrote:

Yes I've arleady downloaded the manuale. Nothink change if I press the on board switch. Here there is a link the scope dissasambled.
Link: http://www.mediafire.com/?b3y1xxgguouod1d
There are any common failure in this psu or some test point into the cpu board?

--- In TekScopes@yahoogroups.com, "jayw_comark" <jayw_comark@> wrote:

Hello,

There is a component level service manual at http://www.ko4bb.com/
for a TDS520B. The power supply may be similar to yours if not the same. You could also try pressing the small button on the CPU board to see if it turns on in case your problem is with the front panel board.

Jay


--- In TekScopes@yahoogroups.com, "alberto.vaudagna" <alberto.vaudagna@> wrote:

Today I've got a TDS540 oscilloscope with options 13, 1M and I think 2F (I don't know exactly).
The problem is it doesn't turn on.
Despite I read a lot of comment regarding capacitor leaking in my unit none of the capicitora are leak. (A lot of fortune!!)
I think it is a psu problem.
When I plug in the power cord and turn on the instrument, nothing happens.
Near the psu I can hear tick-to sound.
Any one have a schematics for that power supply circuit?
The model is: 22904700 rev F.
Any body have some idea on what ca be wrong?
Thanks for the attention.
Best regards, Alberto Vaudagna.


Re: Repair question for Type D High-Gain Differential plug-in

widgethunter
 

Dan,
I have not worked on my type D units, so without looking at the circuit but in general;
Differential amps do rely on closely matched sections. The matching criterium is not transconductance of the tubes as seen by a tube tester, but plate or cathode current in the plug-in's circuit(s). An easy way to determine the tubes' contribution to amp imbalance is to swap them with each other; if the imbalance "follows" the tubes you've isolated that problem. I suspect you'll need to shop for tubes…

Good luck.
Bernd Schroder

Sent from my Verizon Wireless Droid


-----Original message-----
From: Daniel Koller <kaboomdk@...>
To:
"TekScopes@..." <TekScopes@...>
Sent:
Sat, May 18, 2013 13:00:59 GMT+00:00
Subject:
[TekScopes] Repair question for Type D High-Gain Differential plug-in

 

Howdy Folks,

  I'm getting around to repairing my defective plug ins, and I have a question about the type D, for anyone who may be familiar with the circuit.  

  In the output circuit, there is a pair of type 5879 tubes, V3704 and V3604, that are a matched pair.  How close in gain do they have to be to work in this circuit?

  I have three tubes, measured on my Hickok tester as follows:

     V3604 1210 u-Mhos
     V3704  560 u-Mhos
     Spare   975 u-Mhos

  The tube tester specs give 630 u-Mhos as the minimum transconductance for a good tube so V3704 was replaced with the spare.  But I still can't balance the 
amplifier at the most sensitive settings with the grids of the tubes shorted together, as described in the service instructions.  I presume that is because the gains are
so off.  Is this so, or could it be something else?  Is transconductance at a fixed bias enough info to get me a reasonably close pair of tubes without a curve tracer?

  Thanks for the advice.

  Dan


Re: Are deflection plates separate from the tube? Do Tek tubes use wehnelt caps?

Robert Simpson
 

Sorry for the empty message, hit the wrong button.

Someone told me they worked on a 1950s computer that used a mercury pool as a delay line. One end would generate a wave and the other end would detect the wave with the transit time being the delay.

Try and get that around ROHS!
Bob

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



--- In TekScopes@yahoogroups.com, Don Black <donald_black@> wrote:

What I call lumped (artificial) delay lines are delays made of a number
of discrete inductors in series with capacitors to ground (or the
complimentary side) rather than a cable using its natural inductance and
capacitance. In the case of the deflection plates, they are made of a
number of short segments coupled with small coils and trimmer capacitors
from each one (segment) to trim them). Of course you need a special
vacuum screwdriver to adjust them through the glass without losing the
vacuum (joke). Tektronix usually used a coiled coaxial delay line for
the signal delay to allow viewing the leading edge of a signal. However
artificial delays can also be used. We used to have a 3M dropout
compensator for video recorders which had to delay one horizontal line
of signal. I was switchable for the different standards, up to 100 µs
for 405 lines and it had row upon row of coils making up the delay lines.
Others more familiar with Tektronix please jump in and add or correct me
as you see fit please.

Don Black.

On 17-May-13 7:19 PM, cheater00 . wrote:

Regarding delayed deflection plates.

What is the basic operation of the lumped delay line circuits? Is it
just a long delay cable with a network which compensates the
impedance?

Regarding the digital vs analogue cancer that spread into this
conversation:

On Fri, May 17, 2013 at 6:10 AM, Steve <ditter2@
<mailto:ditter2%40yahoo.com>> wrote:
Modern real time scope run up to 65 GHz. No analog scope could get
within an order of magnitude of that. And few applications simply look
at a Y-T waveform. I use fast RT scopes every week for tasks such as
decomposing jitter components in serial data streams running at 28
gigabits per second. I can easily measure these down to 300
femtoseconds, with an accurate resolution of 50 femtoseconds or so.
Users buy digital scopes for their analysis capability, seldom as a
replacement just to look at waveforms that an analog scope could do.

I love old analog scopes for their place in history. They are fun to
restore. It is not different then people who restore antique autos.
May of these had design features that were decades ahead of their
time. But no one claims that an antique auto has the utility or
reliability of a modern car that gets you to work every day.

The tasks that design engineers need to perform today simply can not
be performed by an analog scope.

<rant>
Because everyone is just like you and has exactly your job, right? Let
me tell you, in 100% of my use of an oscilloscope I don't need *any*
of the doohickeys you mentioned. And even if I took the technical
level of my work to the very frontier of what's being done today, I
still wouldn't need any of it. Who cares about 300 picosecond jitter
when designing analogue audio circuits? You've got to be out of your
mind to think everyone needs 65 GHz bandwidth (so why bring it up at
all). My area, audio circuit design, will forever be fine with a 200
MHz bandwidth analog scope, maybe with minimal digital or analogue
storage capabilities. There are loads, loads, loads other areas in
technology which don't need *anything* provided by digital scopes.
Electrical and electronic engineers of all kinds and types have needs
that are simply not provided for by a digital scope, while the digital
scope provides a lot of stuff they expressly do *not* need. The same
goes for hobbyists: very few end up needing high bandwidth; if an eval
board or kit is provided you don't need to care about clock lines
being bad. There's a huge amount of those people, and I dare say many
more than those who need 65 GHz scopes.

It seems like you think the moment NASA started building the space
shuttle everyone stopped building, using, and servicing bicycles. What
a load of junk. Look at your wrist watch or your mobile phone. Think
that needs a 65GHz scope to build?
</rant>

Please let's not derail this topic further. If you or anyone else
wants to continue the DSO vs CRO conversation, open up your own thread
(which I likely won't take part in).

Kill it with fire.


Re: Are deflection plates separate from the tube? Do Tek tubes use wehnelt caps?

Robert Simpson
 

--- In TekScopes@yahoogroups.com, Don Black <donald_black@...> wrote:

What I call lumped (artificial) delay lines are delays made of a number
of discrete inductors in series with capacitors to ground (or the
complimentary side) rather than a cable using its natural inductance and
capacitance. In the case of the deflection plates, they are made of a
number of short segments coupled with small coils and trimmer capacitors
from each one (segment) to trim them). Of course you need a special
vacuum screwdriver to adjust them through the glass without losing the
vacuum (joke). Tektronix usually used a coiled coaxial delay line for
the signal delay to allow viewing the leading edge of a signal. However
artificial delays can also be used. We used to have a 3M dropout
compensator for video recorders which had to delay one horizontal line
of signal. I was switchable for the different standards, up to 100 µs
for 405 lines and it had row upon row of coils making up the delay lines.
Others more familiar with Tektronix please jump in and add or correct me
as you see fit please.

Don Black.

On 17-May-13 7:19 PM, cheater00 . wrote:

Regarding delayed deflection plates.

What is the basic operation of the lumped delay line circuits? Is it
just a long delay cable with a network which compensates the
impedance?

Regarding the digital vs analogue cancer that spread into this
conversation:

On Fri, May 17, 2013 at 6:10 AM, Steve <ditter2@...
<mailto:ditter2%40yahoo.com>> wrote:
Modern real time scope run up to 65 GHz. No analog scope could get
within an order of magnitude of that. And few applications simply look
at a Y-T waveform. I use fast RT scopes every week for tasks such as
decomposing jitter components in serial data streams running at 28
gigabits per second. I can easily measure these down to 300
femtoseconds, with an accurate resolution of 50 femtoseconds or so.
Users buy digital scopes for their analysis capability, seldom as a
replacement just to look at waveforms that an analog scope could do.

I love old analog scopes for their place in history. They are fun to
restore. It is not different then people who restore antique autos.
May of these had design features that were decades ahead of their
time. But no one claims that an antique auto has the utility or
reliability of a modern car that gets you to work every day.

The tasks that design engineers need to perform today simply can not
be performed by an analog scope.

<rant>
Because everyone is just like you and has exactly your job, right? Let
me tell you, in 100% of my use of an oscilloscope I don't need *any*
of the doohickeys you mentioned. And even if I took the technical
level of my work to the very frontier of what's being done today, I
still wouldn't need any of it. Who cares about 300 picosecond jitter
when designing analogue audio circuits? You've got to be out of your
mind to think everyone needs 65 GHz bandwidth (so why bring it up at
all). My area, audio circuit design, will forever be fine with a 200
MHz bandwidth analog scope, maybe with minimal digital or analogue
storage capabilities. There are loads, loads, loads other areas in
technology which don't need *anything* provided by digital scopes.
Electrical and electronic engineers of all kinds and types have needs
that are simply not provided for by a digital scope, while the digital
scope provides a lot of stuff they expressly do *not* need. The same
goes for hobbyists: very few end up needing high bandwidth; if an eval
board or kit is provided you don't need to care about clock lines
being bad. There's a huge amount of those people, and I dare say many
more than those who need 65 GHz scopes.

It seems like you think the moment NASA started building the space
shuttle everyone stopped building, using, and servicing bicycles. What
a load of junk. Look at your wrist watch or your mobile phone. Think
that needs a 65GHz scope to build?
</rant>

Please let's not derail this topic further. If you or anyone else
wants to continue the DSO vs CRO conversation, open up your own thread
(which I likely won't take part in).

Kill it with fire.


Re: Puzzle of the day: 465b will not trigger on channel 2 SUCCESS!

Robert Simpson
 

Congratulations on sticking with it. Yes, this is a great group who have helped me many times.
Bob

--- In TekScopes@yahoogroups.com, "jeffbathwater1" <jeffbathwater@...> wrote:

You are a genius!
I just happen to have a 2N3906 in my junk box... I now have two rock steady traces! Thank You!
I will track down the proper replacement but for now it looks like this will get me going.

What a neat group!

Dave

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

I looked the transistors up earlier. Q1746 and Q1954 have an Ft of
900 MHz, Ccb of 3 pf, and are similar to a 2N4258 or PN4258.

Any PNP RF transistor like an MPSH81 should work but you can use
2N3906 transistors temporarily. Matching is not needed because
adjusting R1835 will trim out any offset.


Re: Tektronix R7844 Problem: can not set intensity and focus

 

Don't forget that these diodes need to have fast Trr times because they run at 10's of kHz switching speeds.
 
Tom
 

----- Original Message -----
From: Tom Jobe
Sent: Saturday, May 18, 2013 11:16 AM
Subject: Re: [TekScopes] Re: Tektronix R7844 Problem: can not set intensity and focus

 

Just for a reference point.
A small 12 kV diode I just tested has a forward voltage drop of 25 volts at 5 mA, and it has a 35 volt forward drop at 10 mA.
The data sheet for 2CL73, 12 kV diode rates it at a 37.5 volt drop at 10 mA
tom jobe...
 
 
 
----- Original Message -----
Sent: Saturday, May 18, 2013 7:58 AM
Subject: [TekScopes] Re: Tektronix R7844 Problem: can not set intensity and focus

 

Hello:

If this 12kV diode is made up of 30 diodes in series, each with 0.6V forward bias voltage, then it will start to conduct at 18V, right?

Simple DMM test would not yield meaningful result because the supply voltage is too low to make them conduct, that explains! Thank you.

Y.-J. Wu

--- In TekScopes@..., Göran Krusell wrote:
>
> Hi, 12kV diodes are made up by a number of series diodes and therefore your test has failed. Your diodes may
> very well be ok.
> Göran
>


Re: 576 Curve Tracer HV Transformer Rebuild

Glydeck
 

I'm in the market for a 576 HV transformer as well.

George

On May 18, 2013, at 8:29 AM, "drawding@..." <drawding@...> wrote:

 

First I apologize to everyone for the triple post on the original message. I am not sure how that happened. it might have been because I had several different tabs with the TekScopes group opened.

Chuck,

I have been on the list for about 3 months or so. I am very thankful for all the helpful people on here. II am currently repairing a 576, The posts on the 576 have been very helpful. I have been hesitant to post my symptoms because I want the learning experience of figuring it out myself. : ) I have been working on it off and on for a couple of weeks.

One thing I know for sure is that I need a new HV transformer and I would prefer not to take a newer one out of another broken 576 (as it is likely repairable ... if the CRT is good).

So in the interest of supporting the list and everyone with a 576 with an older HV transformer that has failed or getting ready to fail, please contact me off list and maybe we can work something out. I am a highly motivated buyer. I might even be able to go say... two or three dollars over $50. Just think of all the 576s you will save. : )

Thank you,
Dave

--- In TekScopes@..., Chuck Harris wrote:
>
> I'm working on it... but life keeps intervening.
>
> Bill Schell retired from winding about 10 years ago.
> Proof that he is way smarter than me!
>
> The whole winding business seems like it should be
> profitable, but in reality there are about 2 hours
> in each transformer... and we live in a world where
> the scopes aren't worth 2 hours billed at any member
> of the group's labor rate.
>
> So, I will finish my winder when I can steal enough
> time from the work that pays the bills...
>
> -Chuck Harris
>
> drawding@... wrote:
> > Hello,
> >
> > I read all the posts I could find on replacing or rebuilding the high voltage
> > transformer for the 576. So far I have found two options.
> >
> > Chuck Harris
> >
> > (I am not sure if he ever updated his winding machine to work for winding the 576
> > HV transformer).
> >
> > Bill Schell, AA4AY 10102 Winder Trail Orlando, FL 32817 Phone (407) 282-4289
> >
> > This contact is listed on Bill and Stan's Tektronix Resource site for rewinding
> > 547 transformers. Can Bill Shell rewind 576 transformers?
> >
> > Are there any other options out there (other than finding a replacement)?
> >
>


Re: 2465B Source code..

lazystrings
 

You can probably find that using an Eprom programmer reading the contents of the DS1225Y and then go to the calibration routines but perform each CAL individually and see what changes in memory. I don't know if is possible to read the contents of the RAM using the GPIB if you have the option. Lots of things are stored in that RAM and they change each time you turn the Scope on.
You can also read the contents of the Eprom U2360 on the A5 board and disassemble the code. I think that the processor U2140 is a 68A02. That could be a fun project :)

--- In TekScopes@yahoogroups.com, "macgregor54" <fauxscot@...> wrote:

Hi folks....

I made an acquaintance from across the pond who is looking to hack his 2465B cal setting so as to avoid having to do the entire calibration routine.

i have managed to obtain actual source code for 2600 series personal Fourier analyzers and I was wondering if anyone here has it for the 2465b? I know it's a long shot, but I managed to get the 2600 code after a multi-year search once i found some principal engineers, and i was hoping to find someone here who perhaps worked on the product line, or who had a map of the cal NVRAM contents.

What say you, wizards of Tek-ness? Any 2465B gurus, former Tekkies, gifted hackers, etc. in the group? I think this is one of their abandoned products, and it would unlikely involve any copyright issues, if that's a concern.

All leads much appreciated.


Re: 576 Curve Tracer HV Transformer Rebuild

drawding@pacbell.net
 

First I apologize to everyone for the triple post on the original message. I am not sure how that happened. it might have been because I had several different tabs with the TekScopes group opened.

Chuck,

I have been on the list for about 3 months or so. I am very thankful for all the helpful people on here. II am currently repairing a 576, The posts on the 576 have been very helpful. I have been hesitant to post my symptoms because I want the learning experience of figuring it out myself. : ) I have been working on it off and on for a couple of weeks.

One thing I know for sure is that I need a new HV transformer and I would prefer not to take a newer one out of another broken 576 (as it is likely repairable ... if the CRT is good).

So in the interest of supporting the list and everyone with a 576 with an older HV transformer that has failed or getting ready to fail, please contact me off list and maybe we can work something out. I am a highly motivated buyer. I might even be able to go say... two or three dollars over $50. Just think of all the 576s you will save. : )

Thank you,
Dave

--- In TekScopes@yahoogroups.com, Chuck Harris <cfharris@...> wrote:

I'm working on it... but life keeps intervening.

Bill Schell retired from winding about 10 years ago.
Proof that he is way smarter than me!

The whole winding business seems like it should be
profitable, but in reality there are about 2 hours
in each transformer... and we live in a world where
the scopes aren't worth 2 hours billed at any member
of the group's labor rate.

So, I will finish my winder when I can steal enough
time from the work that pays the bills...

-Chuck Harris

drawding@... wrote:
Hello,

I read all the posts I could find on replacing or rebuilding the high voltage
transformer for the 576. So far I have found two options.

Chuck Harris

(I am not sure if he ever updated his winding machine to work for winding the 576
HV transformer).

Bill Schell, AA4AY 10102 Winder Trail Orlando, FL 32817 Phone (407) 282-4289

This contact is listed on Bill and Stan's Tektronix Resource site for rewinding
547 transformers. Can Bill Shell rewind 576 transformers?

Are there any other options out there (other than finding a replacement)?


Re: Rant: Analog vs Digital

Michael A. Terrell
 

I used to volunteer a half day a month at a local Vocational school's electronics course, and gave the students access to my collection of databooks and most of the parts I had. A lot of days one or more would show up with questions, or looking for a couple parts. Some, just to sit and look at what ICs were available. I love that most datasheets are available online, but you have to know what part number you're looking for. That course was shut down but I'm still willing to help when I can, but I only have a small shop at my home these days. I'm in North Central Florida.

-----Original Message-----
From: Peter Gottlieb <hpnpilot@verizon.net>
Sent: May 18, 2013 8:43 AM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: Rant: Analog vs Digital

We can't change today's MBA mindset but we can help young engineers from our own
collections whenever possible.
Michael A. Terrell


Re: My 2465B DM Story

lazystrings
 

I have all the parts and PCB to put together Jim Williams pulser. I will probably use a function generator and a transformer to calibrate the ACV on the DMM. I think I have to be able to generate 450VAC so I need a 50 to 1 ratio transformer. I'm sure I have something in my big junk pile :)

--- In TekScopes@yahoogroups.com, "vdonisa" <vdonisa@...> wrote:

In the absence of the the instruments you mentioned, you can use a known-to-be-good DMM as a reference, connected in parallel to the one you're calibrating.

A square wave generator with stable, calibrated frequency will help too.

The biggest problem I can see is to find a substitute for the tunnel diode pulser fixture. Fortunately we currently have some good threads about repairing/building one.

--- In TekScopes@yahoogroups.com, "lazystrings" <casinada@> wrote:

I was able to calibrate some parts of the DMM : DCV, ACV, HI OHMS, and LO Ohms. I don't have equipment to generate more than 15VAC so I'm stuck there. Does anybody from the group live in Arizona and has a Fluke 5101 or similar Calibrator? of course A leveled sine wave generator and a time mark generator would be great too :)

Still have to calibrate quite a few things on the scope side. The vertical is very good but the horizontal has some scales that are out of cal.

--- In TekScopes@yahoogroups.com, "lazystrings" <casinada@> wrote:

I repaired the broken trace and programed the new DS1225AD and now the scope works fine but is out of calibration. The vertical measurements are fine but the frequency measurements are off on some scales and always off when measured automatically or with the cursors.
The DMM is out of Cal as well.
--- In TekScopes@yahoogroups.com, "lazystrings" <casinada@> wrote:


Just a quick update:
C1034 Measured 4.74uF and the ESR was 1.1 ohms. I don't think the cap was bad but it was part of the recap.

I found that A9 trace pin 24 was severed right between the pad and the trace. I will repair it tonight.
I also found that there is a resistance of 38 Ohm between +5V and GND coming from the LVPS Connector J251 but the voltage is correct.
Thank you
Daniel




--- In TekScopes@yahoogroups.com, "vdonisa" <vdonisa@> wrote:

Hi Daniel,

Do you remember the ESR of C1034? I'm asking since I've seen several reports on this however by looking at several datasheets of capacitors of this type, I've seen ESRs of 2 to 8 Ohms mentioned, depending on manufacturer / series.

And a question for the group: I've seen R1010 open too, and I've seen it mentioned several times by other people. What exactly is the failure mechanism? Mine didn't have any (dis)coloration that would suggest sustained high temperatures (photo here: http://groups.yahoo.com/group/TekScopes/photos/album/1314606778/pic/708477577/view ). I believe it's happening through some fast mechanism - a transient high current that helps evaporate the metal film in a very short time. Anyone that has a good theory about what's going on there?

Thanks,
Valentin VE3VDO


--- In TekScopes@yahoogroups.com, "lazystrings" <casinada@> wrote:

I got a Tek 2465B DM to repair just for fun. The tantalum capacitor C1034 had high ESR and R1010 was open (15ohm)


Re: Tektronix R7844 Problem: can not set intensity and focus

Tom Jobe <tomjobe@...>
 

Just for a reference point.
A small 12 kV diode I just tested has a forward voltage drop of 25 volts at 5 mA, and it has a 35 volt forward drop at 10 mA.
The data sheet for 2CL73, 12 kV diode rates it at a 37.5 volt drop at 10 mA
tom jobe...
 
 
 

----- Original Message -----
Sent: Saturday, May 18, 2013 7:58 AM
Subject: [TekScopes] Re: Tektronix R7844 Problem: can not set intensity and focus

 

Hello:

If this 12kV diode is made up of 30 diodes in series, each with 0.6V forward bias voltage, then it will start to conduct at 18V, right?

Simple DMM test would not yield meaningful result because the supply voltage is too low to make them conduct, that explains! Thank you.

Y.-J. Wu

--- In TekScopes@..., Göran Krusell >
> Hi, 12kV diodes are made up by a number of series diodes and therefore your test has failed. Your diodes may
> very well be ok.
> Göran
>

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