Is it all ways there .. even with beam finder ?
intensity?


On 10/01/2014 02:41 PM, Andrija Ifkovic aifkovic@yahoo.com [TekScopes]
wrote:

No other suggestions? Googling didn't produce much more information
other than it may be related to high voltage stability - one person
replaced diodes and capacitors in the switching PS (voltage
quadrupler) to get rid of a similar looking problem but on a
completely different non-Tek scope. On 2335 those are all under a
metal shield and not even marked on schematics (they show diodes but
not what they are and there is no part id either).

--
Mike KC7NOA

On Sat, Sep 27, 2014 at 5:12 PM, Andrija Ifkovic <aifkovic@yahoo.com> wrote:

So I replaced the Zener, it was a nerve-wracking experience and a hack job. Unfortunately it did not help, after 10+ minutes of beautiful screen the ghosting came back. The only thing I noticed is that if I push out the 10X magnifier button on the scope (so that it's disengadged), then the ghosting is far less visible at any brightness and you can probably say it looks fine. Maybe that gives a clue as to what's going on?

Are you saying you only see the ghosting with the magnifier on? If
so, I don't think there is anything wrong with your scope, that's just
how the scan expansion CRT works.

No other suggestions? Googling didn't produce much more information other than it may be related to high voltage stability - one person replaced diodes and capacitors in the switching PS (voltage quadrupler) to get rid of a similar looking problem but on a completely different non-Tek scope. On 2335 those are all under a metal shield and not even marked on schematics (they show diodes but not what they are and there is no part id either).

Pickup or freight only in San Diego. Needs repair.
Ebay 390943192224

No affiliation.

Jay

It is a 151-0341-00 or 2N3565.

On 10/1/2014 5:35 AM, Mark Wendt mark.wendt.ctr@nrl.navy.mil [TekScopes] wrote:

On 09/30/2014 09:11 PM, Manfred Mornhinweg manfred@ludens.cl [TekScopes]
wrote:

Dear all,

what did you do before you got your first Tek scope? How did you get by in life?
How could you even survive?

I've built several, two from scratch, and some that were almost totally reworked heathkits.
Things are much easier if you start with a low deflection voltage CRT like a 3WP1.

Most of the "cheepy" scopes got their high voltage from a winding on the power transformer
and this is just so bad on so many levels.
I had some very good "dumb" luck in adapting flybacks from small TVs for this purpose.

My first real scope was a Raytheon (Cosser) 50MHZ portable which is still working well today.
My first good Tek, I don't put 2213/15(s) in that spot, was a 465M which I now have too many of.
As a side to Mark Wendt, did you work with any "M"s in the AF?

Like many others on this list I'm now trying to "thin the herd".

Bert

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On 09/30/2014 09:11 PM, Manfred Mornhinweg manfred@ludens.cl [TekScopes] wrote:

Dear all,

what did you do before you got your first Tek scope? How did you get by in life?
How could you even survive?

If you want to read about one of the sins of my long gone youth, have a look at
this page, which I completed and uploaded just minutes ago!

http://ludens.cl/Electron/scope/scope.html

Manfred

Manfred,

I'm in awe. That's just pure genius! Well done!

I never had a scope of my own till a few years ago. When I was a kid, like your poor, undeserving student, I had no money to speak of. My neighbor down the road got me interested in electronics (he was a ham) and also model airplanes. He had a Heathkit scope on his bench that he'd made. We eventually built (as a buddy project) a model airplane radio control transmitter and receiver. Had a lot of fun doing that, and he was a heck of a good teacher. After graduating from high school, and piddling around in college for a few years not really sure of the direction I wanted to take in life, I ended up enlisting in the USAF, and becoming an avionics communications and navigation tech, working on everything from tube receivers to solid state stuff, and eventually on data-link and IR/TV guidance systems. I eventually finished up my degree while still in the USAF, got my commission as a 2nd Lieutenant, went to flight school, got my wings and flew F-4's for the rest of my career in Uncle Sam's Great Fraternal Flying Club. Fast forward a few years, got hooked up with another old retired electronics nut through our hobby of machining stuff, and he pointed me to all the Tek scopes and "stuff" on Ebay. First Ebay purchase was a 7623. Then a TM504. Then plugins to calibrate. Then other plugins like the SC series of scopes. Then a 7603 with a Spectrum Analyzer. Then a 7854. Then some HP equipment.

Oy. What have I gotten myself into?

Mark

.. brings back some memories of my first scope, which I built aged 14 in
the 70's......

I had picked up a scope chassis, tube and mains transformer at a radio
rally - a friend of mine found a circuit diagram of a Heathkit 2 valve
scope, which I copied as far as I could - I developed about 600V for the
CRT using a voltage doubler off the 300V winding - the "PCB" was an old
IF strip from a Murphy TV - I removed the original components, leaving
just the ceramic PCB mount valveholders and rebuilt using the existing
holes and tracks (cut & link where necessary!) - the components were
mainly stripped from old TVs (including the valves) - my first "scope
probe" was a length of thin coax stripped from a TV, terminated in a
wire point and encased in an old BIC biro tube!

That scope went a long way towards my understanding of oscilloscope use,
and general electronics, so I suppose it was worth every penny of what I
didnt spend on it....(!)

Wish I had a photo of that one now!

This was eventually replaced by an ex-army (valve) scope from another
radio rally, which was then replaced by a more modern unit - but both
the valve scopes went to good friends to help them further their
electronics hobbies.... so maybe they are still out there somewhere?

Best Regards

David Thomas


On 01/10/2014 02:42, 'Phil Sittner' sittners@sbcglobal.net [TekScopes]
wrote:

Manfred-

What an impressive project. The old adage "necessity is the mother of
invention" and it is certainly true in your case. I'm thrilled to have
seen it.

Phil
kd6rm
----- Original Message -----
From: Manfred Mornhinweg manfred@ludens.cl [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Tuesday, September 30, 2014 6:11 PM
Subject: [TekScopes] Homebrew scope

Dear all,

what did you do before you got your first Tek scope? How did you get
by in life?
How could you even survive?

If you want to read about one of the sins of my long gone youth, have
a look at
this page, which I completed and uploaded just minutes ago!

http://ludens.cl/Electron/scope/scope.html

Manfred

========================
Visit my hobby homepage!
http://ludens.cl
========================

Hi Manfred and gang

What a fantastic write up, many thanks for taking the time to share it with us.
It brings back memories of the PW (Practical Wireless magazine) Student that I built while at school in the '70s, it had a bandwidth of a few 100kHz and never did work very well, even though my dad took it into his lab at work to let the techs there have a go at it. The tube in that was a 3BP1 and as I recall I was able to make a lot of the chassis during metalwork class !
I keep seeing that copy of PW turning up on Ebay.
During my first job my bench scope was a little Hameg 207 and during my second job, I was given a Tek 465 :o)) and this was with me until fairly recently when I was able to swap it for a 2245A. A t this point I realy caught TAS (Tek acquisition syndrome) and have a growing selection.
Thanks again for the great write up.

Cheers

Paul

Ok, I now know more about a DM501 than I ever thought I would. It started
with a bad latch, progressed to blown power supply transistors, and
wrapped-up with a blown floating supply as well. I then proceeded to pop a
couple of 7474's and one or two 7400s. At that point all I had to fix was
a blinking display. I then popped the power supply again as well as
floating power. After getting the floating supply back up, giving up twice
and buying two more in the process, I was finally able to get a display of
all zeros that wasn't blinking.



The next 16 hours or so found me tracking down a 2n3904 the repairman
soldered into the tightest spot on the board instead of a 3094. I'll tell
you, the guy fixing this thing (me) is an idiot.



Once that transistor was replaced with the correct type I am back to a solid
display with one bug - the OL function isn't working. You might remember
that at one point I had nothing but OL. The irony of the situation makes me
want to pitch the stupid $9 voltmeter down the hill.



How hard can the OL function be to fix? Who the hell needs OL anyway!



The interesting thing is this DMM listed for $495 in 1973, 42 years ago. At
3.7% compounded that is $2,277 in todays money. It is basically a TTL
analog to digital converter with some decent components in it.So now I can
put three dual tracking supplies with meters in this frame pretty cheaply,
maybe a total of $200 invested.



Thanks to all those that sent me pointers and for reading this far.



Jerry



_____

From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Sunday, September 28, 2014 5:14 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] DM501 constant blinking display





On 28 Sep 2014 13:07:25 -0700, you wrote:

I hooked it to my voltage and meter standard and it displayed perfectly. I

then went to extract the probes and it pulled from the frame and your's
truly pushed it back in. So I spent about 5 hours trouble shooting until I
find a blow transistor, replaced it, and powered on.

Doh!

It now displays perfectly but the screen blinks constantly. I checked all

the voltages and they are in spec. It's like it has a stuck bit or
something. I would say the blink rate is about 1/2 second.

I searched the manual and the only time it should blink is when it is OL,

no?

That is the way I understand it. It should blink if the number of counts is
greater than 19,999. The theory section on page 2-5 points to U325B as being
in
the circuit path for controlling the blinking. I assume that the level at
pin 3
of U330 is going low.

I retired from the USAF in 1956 after 4 long years in Albuquerque, NM
and took a job as an electronics technician for IBM in Kingston NY. I
eventually wound up as a bench technician working on transistor
circuits. I was young and picked up on transistor circuits rapidly as,
like all the engineers there, I did not have to un-learn the voltage
sensitive vacuum tube technology to work on the 'new', current sensitive
transistor circuits. I was given one of the first Tektronix 541
oscilloscopes. I rapidly fell in love with it. It was fairly flat to
20 MHz (Mega cycles in those days) and had a fantastic rise time of 20nS
(20muS in those days). I wanted one in the worst way but the selling
price was way out of my ballpark. So, I decided to make one. I started
by accumulating used parts from any source available. I laid out the
main board with the horizontal circuits in the front and the power
supply in the rear. I made a CA, K and the pulser plug ins and made
the vertical plug in to go in the upper right corner, the delay line
going across the back and up the left side to the CRT. I wound the
delay line on 1/4" plastic rod and used 1.5-7pF (uuF in those days)
across the various taps. The CRT was a 5BHP11 which did have input pins
around the neck. I left IBM in 1959 to get an EE degree at UNM in
Albuquerque. The scope by then had changed to a 545D with the addition
of a Tek made surplus delay board which I put on the left front side of
the scope. This became my senior project. I used that scope until
about 2000 when I started buying and refurbishing Tek 4XX series of
scopes. I no longer needed the 545D so I passed it on to Stan Griffiths
to display in his Tektronix museum in Portland.

My vacuum tube days are a thing of the past but my present collection of
over 200 Tek 4XX scopes now occupies much of my time and garage. I
usually have one or two on eBay at any given time.

Would I do it over again? I cannot honestly answer that question. It
got me a job offer at Tektronix in 1964 after I completed my BSEE but I
turned Tek down and started on my MSEE. I just could bear the thought
of leaving sunny Albuquerque for rainy Portland and I was also accepted
in the masters program at UNM.

I will try to attach a photo of the front of the 545D to this note. If
the photo does not come through, and you are interested in more details,
write me at reed714@sbcglobal.net.

Reed Dickinson

This applies to any of the regulators which use the external pass transistors
but you can do it with a PS-50x power supply. The easy way uses a function
generator, oscilloscope, and resistive load.

The load is attached to the output of the power supply so it is roughly 1/2 of
the rated current at the 1/2 of the rated voltage. Then the function generator
is used to produce a low frequency small amplitude square wave which is AC
coupled into the non-inverting input of the voltage or current error amplifier
depending on which you want to test. You can then directly see the positive and
negative transient response on the output using an oscilloscope.

If you really know you stuff, you can estimate the bode plot from the waveform
and with the right kind of oscilloscope, you can calculate the bode plot by
differentiating the transient response and applying an FFT which is why I would
really like a DSO capable of doing that.

I had a Lavoie LA-265A oscilloscope found at a garage sale which is a clone of a
Tektronix 545A.

Manfred,
SPECTACULAR! I hope we get to meet some day. We have a lot to talk about. I
was hooked when I rebuilt a Dumont scope.

David is right about Reed. There are more than a few like him and you.
Barrie Gilbert is one of the most famous. Barrie built his own sampling
scope which really impressed the folks at Tek.
Dennis Tillman W7PF

At 09:11 PM 9/30/2014, Manfred Mornhinweg wrote:

what did you do before you got your first Tek scope? How did you get by in life? How could you even survive?

I had Teks at work, but before I bought a 453 for myself I owned an HP 141A with the 20 MHz vertical plugin. The Tek 453 was used in both home shop and in the field for more than a decade, but the 453 now lives in the shop as I now own an HP 1740A for the field.

That is one of the best looking homebrew 'scopes that I've seen. When did you build it?

Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcity/radios/index.html

Indeed that is an impressive project.

My first was an Eico kit my parents got me as a birthday gift. I was probably about the same age, 11 or 12. It used tubes and I remember it not working when I built it, which I traced down quickly to a bad 6X4 rectifier tube. It didn't have triggered sweep. I did a bunch of tweaks on it over the years and have no memory of what happened to it. My parents liked order and hated clutter so occasionally batches of my stuff would disappear. When I was about 15 I got a huge HP two channel sampling scope at this store on the south side of Canal St in NYC for $100. I spent a lot of time messing with it and eventually totally messed it up trying to convert it to a regular scope. I think when I was 18 or so a friend sold me a Tek 485 which after a bit of fixing and cleaning lasted me a while until it ended up getting stolen from my van down in NC (along with much of my better stuff as well).

The surplus market has been good to me over the years. Now I have way too many scopes but I have a few Tek ones (2465B, R7103, 7844, 2235 etc) which each have a purpose and are keepers.

Peter

That's pretty cool.

My first 'scope was a Dumont. I don't remember the model. It was given
to me when I was about 11 or 12 years old (say, 1968 or so) by my uncle
who worked for Fisher Scientific. My friends in grade school thought I
was weird, but they thought the 'scope was "cool". I didn't know quite
what to do with it, but I had fun hooking it up to circuits and viewing
waveforms. It had continuously variable vertical and horizontal
controls, so one had to have a reference to make precise measurements.

I wish I still had it.

I didn't get a Tektronix 'scope until the early eighties, when I got a
465 and paid way too much for it. I still have that one. Someday I plan
to give it to my nephew.

DaveD

On 9/30/2014 7:11 PM, Manfred Mornhinweg manfred@ludens.cl [TekScopes]
wrote:

Dear all,

what did you do before you got your first Tek scope? How did you get
by in life?
How could you even survive?

If you want to read about one of the sins of my long gone youth, have
a look at
this page, which I completed and uploaded just minutes ago!

http://ludens.cl/Electron/scope/scope.html

Manfred

========================
Visit my hobby homepage!
http://ludens.cl
========================

Manfred-

What an impressive project. The old adage "necessity is the mother of invention" and it is certainly true in your case. I'm thrilled to have seen it.

Phil
kd6rm

Do you mean at the power supply (e.g., PS-5-something) output?