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Hello Saroj,

the high pitch sound should indicate it is trying to oscillate and turn on the FET.
The one you have should be OK too.

The thing is, the inrush current of these switch mode PS is very high, so it could be the bulb preventing it to switch on properly...

If you don't find any obvious shorts around the FET and other transistor, I would try it without the bulb...
Connect a voltmeter to the expected 43V and see what happens :-)

Good luck,

Leo

Hi
Did you go through my previous message?
There I described some of the activity and results.
I appreciate if you comment on that.
Thanks saroj

Hi,

I think that should be ok.
As far as I can see in the 494 the reference has a bit more room, compared to the 595.
But being in the first stage of the power supply, maybe it's not so critical.

Un saludo, Leo

Reg,

You mentioned "a pair of 106s" - Hewlett-Packard frequency standards? Those
were very accurate quartz standards and hard to find. I once turned up a
couple and they worked but had been heavily modified by some US Government
lab - the fine frequency adjustment was partly removed. I swapped them to a
time-and-frequency guy who wanted them for parts to keep his 106 running. I
have used an HP 107 and have a 105A quartz standard that runs fine. I used
to check the 105 against WWV 60kHz, but am in the process of switching to
GPS as a reference. I have an HP disciplined quartz standard that uses GPS
to keep the quartz oscillator on frequency.

Do you know about the "Time Nuts" folks?

Steve H.





On Mon, Jun 29, 2020 at 9:28 PM Reginald Beardsley via groups.io <pulaskite=
[email protected]> wrote:

On Sat, Jun 27, 2020 at 02:09 PM, Dennis Tillman W7pF wrote:

TekScopes is "All about classic Tektronix test equipment, its use,

repair,

and collecting".

What do comments and opinions about Wikipedia have to do with TekScopes?

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator

WTF!

Discussions drift because people make statements others don't understand
and the explanations often go far afield. It is inevitable.

I was not aware that discussion on TekScopes was restricted to the
cognesceti. If that's the case then I certainly don't belong here.

I own 8-10 pieces of Tek gear and about 20-25 pieces of HP gear. And no
significant experience with any except for a pair of 106s and a 465. And
my recent 11801. It was simply outside my budget until a couple of years
ago when old age set in.

"Collecting" test gear borders on being offensive to me. It seems to be a
TekScopes obsession. I've never seen an "is an xxxx worth restoring?"
post on the HPAK list. These instruments were made to be *used*, not
worshiped.

If TekScopes is going "technically correct" I'm simply going to stop
reading it.

Reg

The discussion of strobe lights and Harold Edgerton brought to mind his
work on the "Rapatronic" shutter which was used to take photographs of
early atomic tests. Here's ab it about the Rapatronic:



If you are interested in seeing some of the photos and more techniques to
film atomic explosions (not trivial since the exposure range was huge)
there's a book titled "How to Photograph an Atomic Bomb" by Peter Curran.
The hardcover edition has gotten very expensive as it is nearly sold out
and won't be reprinted. The softcover edition is less expensive. If you
search the archive of this group, there were some threads from 2017 about
the use of Tektronix scopes for data acquisition during atomic testing.

Steve H.

On Sat, Jun 27, 2020 at 7:44 PM Ed Breya via groups.io <edbreya=
[email protected]> wrote:

In the recent thread about variacs, there was a tangent off to strobe
lights.

Barry wrote:
"Coincidentally, I've been looking at getting one of those over the last
few days. Unfortunate what the bulbs cost for them these days. I suppose if
I watch long enough..."

You can get or build "modern" strobe lights based on high power lighting
type LEDs, and not have to worry about the xenon lamps and powering them
and controlling them. LEDs are much easier to deal with, and with modest
voltages.

A few years ago I did some experimenting with LED strobing as an
attachment to my coil winding machine project. I think I reported it here
in the photos section. If I can find it easily, I'll post a link. Anyway,
with just a small (6-12 LED cluster, don't recall exact size) warm-white
LED module from a lighting fixture, I got decent viewing with normal
ambient light, and had no trouble looking in detail at a router bit
spinning around 25,000 RPM.

I had planned to (eventually) build a scaled up general purpose version
with a large LED array. I have the rough design and parts set aside, but
it's a low priority, since I don't often need a strobe, and I have a nice
old regular Xe one that I had fixed at about that time too. If the repair
of the old Xe had not turned out so easy - the flash head capacitor was
shot , and had an intermittent wire - I would have probably junked it and
built the LED version.

The xenon lamps have the edge in terms of peak power for a single device,
but the LEDs win in terms of rep rate and pulse width control, and color
temperature choice. The LED peak power (drive current) is limited to maybe
3-10 times normal, so you need lots of them for high brightness. They are
easy to scale up in number, and I'm convinced they can way outperform xenon
lamps for strobes.

Anyway, I believe there are by now lots of commercial LED-based strobes
out there, yet another solid-state replacement of a "tube" technology.

Ed

Karl,

Now THAT is what I call very serious restoration work! Nice going!

Steve H.

On Mon, Jun 29, 2020 at 10:49 PM Karl Ireland via groups.io <rf-guy=
[email protected]> wrote:

I restored a Wavetek 1038-NS20 to fully working condition.
It is using these modules: 1038-NS20, D14, NS206, and one labled
"calibrator output" and "ext ref input".

When I bought it on eBay, I found out that ALL the push-buttons had
degraded over time
where they didn't snap in/out when pressed, most of them were permanently
pushed in
which locked up the instrument!

I had to remove the 1038-NS20 module from the frame,
disassemble the 1038-NS20 module,
unsolder all the pushbutton switches,
cut open all the switches,
remove the guts,
put each one on my milling machine & machine the internal area larger,
install a new tiny pushbutton switch inside the original switch body and
solder the connections,
epoxy it in place,
close-up the switch with the original engraved push-button re-installed.
solder the switches back into the PCB,
re-install the PCB into the 1038-NS20 module,
plug the module back into the frame & power it up for a test.
All the buttons worked! This took an entire weekend to do!

Forgot to tell
I replaced u930 by tl 494.

Hi Leo
I am still searching for the component.
I got 4.7 Ohms resistor an 2n5401transistor.
Replaced 39 Ohms resistor and 2n2907.
For the time being I replaced q9070 by irf 830 which is very close to the
one you suggested in terms of switching time
and has better voltage and current performance. For cr 907 I replaced by
two 1n4936 in parallel which has switching time of 200ns which is quite
higher than switching time of Byz73g.
And put the scope on with same current limiter bulb. This time the bulb
lights on continuously bright (does not flash Ann no ticking sound) and I
could hear high pitch sound which is not very loud. But all the voltage
dropped across the limiter bulb. I could get around 7 v across c906. I
might be wrong but what I am thinking is
q907 fired on and never came to off state or there is a dead short in the
preregulator.
Of course I Wil replace those two component when I get them.
Saroj

On Mon, Jun 29, 2020, 3:25 PM Saroj Pradhan via groups.io <sarojman.Pradhan=
[email protected]> wrote:

Hi leo
Thanks once again for guiding me through repair process.
Regarding the voltage issue you are right that my power supply has poor
regulation.
As you suggested I will try my best to replace those component and get
back to you hopefully with good news.
Saroj

On Mon, Jun 29, 2020, 12:52 PM satbeginner <castellcorunas@...>
wrote:

Hello Saroj,

this is a good start! You confirmed your scope has the typical issue,

it's

almost always the primary power supply with problems.

The Power Supply are basically TWO switching inverters after each other.
By means of bypassing the first - what you now did- you narrowed your
problem down to the first one.

First about the fan:
The fan is just a simple 60mm 12VDC fan, and usually draws about
150-160mA, and in the scope its running at a slightly lower voltage.
Did you use the proper polarity when you tested the fan? The board layout
and diodes in the scope create a negative voltage in respect to ground.
But, I assume you unplugged it to test, and if it does not turn and draws
500mA, I would say it is broken.

Smaller scopes in the 22xx range do not even have this fan, so again, for
now leave it disconnected until you got a proper replacement.

The wobbling of the screen, and lower DC voltages in the secondary PS are
probably due to the fact your temporary power supply is not regulated, a
bit low (38,7V) and therefor probably has a significant ripple, I would

not

worry about these things right now.
The most important thing is: the second stage of the power supply works.
:-)

Now we concentrate on the first stage of the power supply:

I looked at all the different versions of the power supplies used in the
2213 2215 2215A 2230 etc scopes, and they are all similar, but not of

great

design (Sorry for this remark, Tek!!)
I choose to use the following approach:

I changed R909 to 4,7 Ohm, instead of 39 Ohm.
This charges and discharges the input capacity of the FET Q9070 faster,

so

it will switch ON and OF faster, therefor it will dissipate a bit less
power during switching.
You will find this lower value of R909 in some f the scopes I mentioned.

Furthermore: I replaced Q9070 by a FQPF4N90C.
This FET has a slightly lower ON-resistance (again, less dissipation

while

ON) AND it has a full plastic housing.

Because of the plastic housing I put it directly on the metal mounting
plate while I added a TO-220 heatsink as well.
I even put a TO-220 heatsink at the other side of the metal plate, to
increase the cooling surface.

Recently I used the following components to repair this power supply:

CR907 MUR460 (a bit difficult, because of the thicker wires on this

diode)

Q908 2N5401 (EBC) same pinout, so easy to replace
Q9070 FQPF4N90C Higher voltage, Lower ON resistance, plastic TO-220
housing, better mounting (IMHO)

But obviously, others will work too.

My first option would be:
Find suitable components, and leave the suspected fan disconnected for

now.

See if it works, and while working on the repair, find another 60mm fan,
maybe from an old PC or other device.

God luck, you will get it up and running.

Leo

On Mon, Jun 29, 2020 at 10:38 AM, Jean-Paul wrote:

Serious users should avoid the Chinese copies and opt for a good condition
used made in USA model mentioned above.

I Jon,

Why should serious users avoid the "Chinese copies" ?? Why should "used" be preferable to new? Are variacs like bottles of wine?

I was a serious competent professional for many decades. After I retired, the "serious" went away and I am simply a competent user. And as such, I have found nothing inferior in my "Chinese copied variac'. Nothing that I see could give problems to my grandchildren when they inherit this variac.

When you plug your brand name made in USA variac into a power strip cord, you make sure that this power strip is also a used cord made in USA and not a copied new Chinese power cord?

Ernesto

Do we really need 20 replies to this?
Dennis Tillman W7pF

Hi Jay,
LOL
Thank you for saying what I was thinking so much better than I did.
That brought a big smile to my face.
Dennis Tillman W7pF

I restored a Wavetek 1038-NS20 to fully working condition.
It is using these modules: 1038-NS20, D14, NS206, and one labled "calibrator output" and "ext ref input".

When I bought it on eBay, I found out that ALL the push-buttons had degraded over time
where they didn't snap in/out when pressed, most of them were permanently pushed in
which locked up the instrument!

I had to remove the 1038-NS20 module from the frame,
disassemble the 1038-NS20 module,
unsolder all the pushbutton switches,
cut open all the switches,
remove the guts,
put each one on my milling machine & machine the internal area larger,
install a new tiny pushbutton switch inside the original switch body and solder the connections,
epoxy it in place,
close-up the switch with the original engraved push-button re-installed.
solder the switches back into the PCB,
re-install the PCB into the 1038-NS20 module,
plug the module back into the frame & power it up for a test.
All the buttons worked! This took an entire weekend to do!

On Sat, Jun 27, 2020 at 02:09 PM, Dennis Tillman W7pF wrote:

TekScopes is "All about classic Tektronix test equipment, its use, repair,
and collecting".

What do comments and opinions about Wikipedia have to do with TekScopes?

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator

WTF!

Discussions drift because people make statements others don't understand and the explanations often go far afield. It is inevitable.

I was not aware that discussion on TekScopes was restricted to the cognesceti. If that's the case then I certainly don't belong here.

I own 8-10 pieces of Tek gear and about 20-25 pieces of HP gear. And no significant experience with any except for a pair of 106s and a 465. And my recent 11801. It was simply outside my budget until a couple of years ago when old age set in.

"Collecting" test gear borders on being offensive to me. It seems to be a TekScopes obsession. I've never seen an "is an xxxx worth restoring?" post on the HPAK list. These instruments were made to be *used*, not worshiped.

If TekScopes is going "technically correct" I'm simply going to stop reading it.

Reg

On Mon, Jun 29, 2020 at 05:30 PM, John Shadbolt wrote:

Thanks Mike, very relevant, I cleaned up the beam finder switch and the
difference between bottom and top height is now 1.8 and 2.5 squares (1:1.4) so
an improvment over 2.5 and 4 squares (1:1.6). Beam finder switches clearly
don't get used much!

Regards,
John

John,

Glad to hear that this helped you.

Exercise all those switches vigorously. My 485 took quite some time to become fully functional. I cleaned and used DEOXIT on the thing about 3 or 4 different times before the trace came fully back as it should be. Make sure to use a cleaner that does not leave residue or attract dust.

There are a lot of these switches on TEK scopes and they all suffer from the same malady. Clean everyone that you can find on your 2215.

I find dirty switches and contacts are the number one cause of scope "failures".

Good Luck with your scope.

--
Michael Lynch
Dardanelle, Arkansas

On Sat, Jun 27, 2020 at 02:37 AM, Michael W. Lynch wrote:

I do not know if this is relevant, but I have a 485 that did a similar thing.
The square wave supplied by the calibrator was fine when the trace was
centered and as you moved the trace away from center, the trace shrank
vertically .. the problem ...a very dirty
beam finder switch.

Thanks Mike, very relevant, I cleaned up the beam finder switch and the difference between bottom and top height is now 1.8 and 2.5 squares (1:1.4) so an improvment over 2.5 and 4 squares (1:1.6). Beam finder switches clearly don't get used much!

Regards,
John

It's a Allen Bradley pot. Low noise and sealed, really good.

p/n 311-0497-00

Hello--

I'm offering FS a trio of books dedicated to electronic strobe and other high-speed
photographic techniques. All three books are mainly of historical interest and hence are
sold in one batch. As you might expect, these books feature lots of cool illustrations
showing spilled milk,? shattered bottles, explosions, hummingbird tongues and more.
Harold Edgerton's name is prominent in the bibliographies.

Science of Electronic Flash Photography, by Kenneth Karsten, Chilton Book Co., NYC, 1968 ed. not stated. 190 pp. indexed, Includes plans for building
strobe power supply and strobe lights. Hardcover in very good cond., dust jacket in VG- minus cond. (small tear on reverse, edge nicks).
Many photos, line drawings and and schematic illustrations. Interior is unmarked. Previous owner's stamp on flyleaf.


"Strobe" The Lively Light, by Howard Luray, Camera Craft Publishing, 2nd ed., 1954. 144 pp. Hardcover boards
in gold finish, in VG condition, dust jacket in good cond (spine wear. edge nicks. Bibliography, index



High Speed Photography, Its Principles and Applications, by George A. Jones,? John Wiley & Sons, New York,
First Edition, 1952. Hardcover ed. in VG condition, 320 pp. index, illustrated.? Describes electronic flash, streak
cameras,film techniques. Extensive bibliography.

I'm asking $18.00 for the lot of three books, which includes USPS media-mail shipment.

Questions welcomed, PayPal honored.

Thanks, and 73--

Brad? AA1IP


P.S.: I may have some NOS strobe tubes FS if anyone is interested.

What is the thing it's sitting on? An adjustable coil?
-Dave

One of our cats loves to pee in interesting places, so the Tek gear stacked in my office always has to have "uncomfortable" items placed on top to keep the cat off.? The other cat I don't have to worry about- the only place she pees is on the floor in front of the litter boxes...
-Dave

Never have found mice, but I did have a problem in Colorado years ago while doing a lot of solo mountaineering. Every night I was sleeping in my car (and I'm sure when I was away too), marmots would gnaw on the underside of my car.? Thankfully, they stuck with the undercoating, and left the wiring and brake lines alone!? I always checked before driving to the next spot.
About the same time, I drove from somewhere in the southern Sierras to Newport beach (SoCal). When I arrived, I wanted to check my oil, so I popped the hood, and something jumped out and ran off.? Probably a large ground squirrel- I'm sure it was really confused, but thankful to be out of the engine compartment!
-Dave