Date   
Re: 11801 diagnostic help

 

On Sat, Mar 16, 2019 at 04:45 PM, Reginald Beardsley wrote:

Hopefully with 11801 manuals in hand rather than manuals for later variants.
Seem to be a hard one to find. I scanned mine and you can find it here for some time:
www.hakanh.com/dl/temp/11801_Service.pdf
It is OCR'ed and bookmarked. Feel free to upload it to TekWiki.
/Håkan

Re: 11801 diagnostic help

Reginald Beardsley
 

Thank you!! I just bought the user manual, so I'll be scanning it when it arrives. There is a paper copy of the service manual on eBay for $35 which I will buy if the seller will verify it is the correct manual, though now that I have a confirmed part number I may go ahead.

But now that I have the correct manual I can at least identify the boards and while I'm at it copy the ROMS.

I found so many 11801C manuals online listed as 11801 it was ridiculous.

Have Fun!
Reg

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

On Mon, 3/18/19, zenith5106 <hahi@...> wrote:

Subject: Re: [TekScopes] 11801 diagnostic help
To: TekScopes@groups.io
Date: Monday, March 18, 2019, 4:54 PM

On Sat, Mar 16, 2019 at 04:45 PM,
Reginald Beardsley wrote:

> Hopefully with 11801 manuals  in hand
rather than manuals for later variants.

Seem to be a hard one to find. I scanned mine
and you can find it here for some time:
www.hakanh.com/dl/temp/11801_Service.pdf
It is OCR'ed and bookmarked. Feel free to
upload it to TekWiki.
/Håkan

2467B No B Sweep

thespin@...
 

Hey All,

I've managed to find some time to play with my 2467B and have been trying to untangle whether the non-working CTT option (CT TEST 86 FAIL 02) has broken the B sweep or if the B sweep itself isn't working at all. Regardless of whether B "RUN AFT DLY" "TRIG AFT DLY" or "TRIG Delta DELAY" is selected, I see "MISSING B TRIG" on screen. I reckon "TRIG AFT DLY" shouldn't work at all since this is what's indicated isn't working by TEST 86 FAIL 02.

So here's what I observe. I get a stable trace using the A sweep. I pull the SEC/DIV knob, turn it one click to the right, and push it back in to switch to the B sweep. I then observe no trace at all, for any position of the holdoff knob, for any value of the DLY value on screen, and for any B trigger setting. This scope is pretty complex and I understand I might just not be using the B sweep correctly... but if indeed this is abnormal behavior, how can I tell if the CTT failure is causing this, or if it's something related to the A/B trigger hybrid, B sweep hybrid, or display sequencer IC? Or perhaps something totally unrelated? Does anyone have any experience with this behavior?

Re: 2467B No B Sweep

thespin@...
 

Okay following the video of w2aew (https://www.youtube.com/watch?v=54roz8IUoVI), I'm now a bit more confident I'm not goofing something up. Pulling the SEC/DIV knob doesn't result in an intensified region, and turning the knob doesn't result in a second trace. I think the B sweep is just out.

On Mon, Mar 18, 2019 at 09:05 PM, <thespin@...> wrote:


Hey All,

I've managed to find some time to play with my 2467B and have been trying to
untangle whether the non-working CTT option (CT TEST 86 FAIL 02) has broken
the B sweep or if the B sweep itself isn't working at all. Regardless of
whether B "RUN AFT DLY" "TRIG AFT DLY" or "TRIG Delta DELAY" is selected, I
see "MISSING B TRIG" on screen. I reckon "TRIG AFT DLY" shouldn't work at all
since this is what's indicated isn't working by TEST 86 FAIL 02.

So here's what I observe. I get a stable trace using the A sweep. I pull the
SEC/DIV knob, turn it one click to the right, and push it back in to switch to
the B sweep. I then observe no trace at all, for any position of the holdoff
knob, for any value of the DLY value on screen, and for any B trigger setting.
This scope is pretty complex and I understand I might just not be using the B
sweep correctly... but if indeed this is abnormal behavior, how can I tell if
the CTT failure is causing this, or if it's something related to the A/B
trigger hybrid, B sweep hybrid, or display sequencer IC? Or perhaps something
totally unrelated? Does anyone have any experience with this behavior?

Re: 222/224 Portable scope CRT pinout?

Jared Cabot
 

Does anyone have one of these they can pop the cover off and take a photo or two, or have the physical pinout of the CRT so I can match up the wires?

Re: 2467B No B Sweep

 

Is it possible the switch isn't operating when you pull the knob out?  There is a plastic piece between the knob and the switch that can be broken.

Re: Storage CRTs fade with age ?

Roger Evans
 

I acquired a non-working 7623A a few months ago which included a few faults in the storage control board with four 74xx ICs having failed, two monostables and two logic ICs. This meant that I actually tried very hard to calibrate the various voltages on the display board and understand how to use the storage modes and it was quite an eye-opener. Yes, the display in bistable mode is a bright background with a slightly brighter signal trace but the 7623A automatically couples the erase cycle to timebase single-shot so you set up levels and triggering with the display cycling every couple of seconds and then you are ready to go for the real single shot event. Fast mode really does work and doesn't degrade the contrast significantly! The contrast is good enough to photograph without any exotic techniques and you can see a single shot signal of two vertical divisions (OK, not that great) with a 5nsec rise time at 5nsec/div sweep speed.

I am old enough to remember using 10000ASA Polaroid film in cameras with sliding backs so that you got up to nine exposures per frame on the very expensive film. With a 10 minute interval between shots you could wait for an hour (without seeing any data) before finding that there was some error and there was nothing on the film!

I also have a 7934A which should be even better but there is some damage to the CRT that prevents fast mode from working.

As Chuck says, storage tubes do not provide the really bright displays of a regular CRT but in moderate lighting they are acceptable and the ones I have (also a 7613) are all very sharp and clear.

Roger

Re: 2467B No B Sweep

thespin@...
 

It’s not. The proper lights come on suggesting the scope is trying to run the B sweep, but it isn’t running.

On Tue, Mar 19, 2019 at 06:57 AM, Manuel Maseda wrote:


Is it possible the switch isn't operating when you pull the knob out?  There
is a plastic piece between the knob and the switch that can be broken.

Re: Test input for an SD-32 sampling head

Mark Kahrs
 

I wrote a "tidbit" on NLTL patents for Microwave Magazine. You can find it
here:

https://ieeexplore.ieee.org/document/7484899

There's quite a bit of history in NLTLs, so one can spend days/weeks
wandering and reading. Don't ask me how I know.

On Fri, Mar 15, 2019 at 2:10 AM Jim Ford <james.ford@...> wrote:

Hi, Reg.

Regarding fast pulses and such, there is a wealth of information at Jim
Andrews' page here: https://kh6htv.com/pspl-app-notes/ He founded
Picosecond Pulse Labs in 1980 and sold it to Tektronix in 2014. I used
PPL products with a CSA803 back in the mid 1990's at Lockheed. I think
the sampling head I used was an SD-24, but since it was about 25 years
ago, my memory is a bit fuzzy.

These days I have a 7904, a 7603, a 7S12, a 7S11, two S-4 sampling
heads, S-53 and S-51 triggering heads, etc in my garage lab. Oh, and a
couple of 10:1 probes I made out of board-edge SMA connectors, 450 ohm
(470 paralleled with 1.8k ohm) 0402 resistors, and 3-pin right-angle 0.1
inch spacing headers. I've not completely characterized the probes, but
at least they pass up to about 12-13 GHz without much attenuation above
the expected 20 dB. Planning to use them to probe some digital RF
boards I'm going to build for work (Raytheon). Too much trouble to try
to get a fast enough sampling scope at work :(

Enjoy the PPL app notes! I've referred to AN-2a through -2e often.

Thanks for the literature references. I'll have to check them out
(someday).

Jim Ford


------ Original Message ------
From: "Reginald Beardsley via Groups.Io" <pulaskite=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: 3/14/2019 6:03:56 PM
Subject: Re: [TekScopes] Test input for an SD-32 sampling head

I have one of Leo's 100 pS impulse units as a source for initial
experiments. If I can narrow that to 10 -20 pS with discrete SMD parts I
may be able to get the idea to work. There's a close connection to the
Hilbert operator hiding in there somewhere.

I've been reading an excellent book on FPGA implementation of DSP by
Roger Woods et al most of the afternoon. So I've not started on the
dissertation yet. I can't really say much else until I understand the
mathematics and physics of using the reverse biased diodes as capacitors.
That should keep me entertained for a few weeks at least.

In any case, failure doesn't matter. It's a hobby project, not a client
deliverable. I've been fascinated by the problem of getting a fast rise
time edge for a long time. It's a bit of circular logic. My excuse for
doing it is I bought an 11801 and my excuse for buying the 11801 is so I
could try to do it. If I can narrow the 100 pS pulse by 5x I'll have an
excuse to buy an SD-32.

I spent 3 years studying sparse L1 pursuits using "A Mathematical
Introduction to Compressive Sensing" by Foucart and Rauhut as a text
followed by reading the original papers by Donoho, Candes et al. Beats the
hell out of watching television. I just wish I could find someone else who
was interested in the subject to discuss it with. It's quite amazing what
you can do with sparse L1 pursuits and really easy to do in practice.
Understanding the math is not easy, but most people use FFTs without really
understanding them.

Have Fun!
Reg


---
This email has been checked for viruses by AVG.
https://www.avg.com



Re: 2467B No B Sweep

Roger Evans
 

You could try swapping the A and B sweep generator hybrids U700 and U900, they are identical part numbers. There should be some recommendations here about cleaning the contacts (carefully!) if the present U900 is at fault. The sweep generator hybrids are relatively low prices on the spares market which suggests they don't fail very oftem!

Roger

Re: Test input for an SD-32 sampling head

Jim Ford
 

Hmm... I've not heard of the tidbits before, although I use IEEEXplore fairly often at work.   I will try it tonight from a real computer.  Not so much fun trying to read serious articles on a little smartphone screen...Thanks, Mark!Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Mark Kahrs <mark.kahrs@...> Date: 3/19/19 8:13 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Test input for an SD-32 sampling head I wrote a "tidbit" on NLTL patents for Microwave Magazine.  You can find ithere:https://ieeexplore.ieee.org/document/7484899There's quite a bit of history in NLTLs, so one can spend days/weekswandering and reading.  Don't ask me how I know.On Fri, Mar 15, 2019 at 2:10 AM Jim Ford <james.ford@...> wrote:> Hi, Reg.>> Regarding fast pulses and such, there is a wealth of information at Jim> Andrews' page here: https://kh6htv.com/pspl-app-notes/  He founded> Picosecond Pulse Labs in 1980 and sold it to Tektronix in 2014.  I used> PPL products with a CSA803 back in the mid 1990's at Lockheed.  I think> the sampling head I used was an SD-24, but since it was about 25 years> ago, my memory is a bit fuzzy.>> These days I have a 7904, a 7603, a 7S12, a 7S11, two S-4 sampling> heads, S-53 and S-51 triggering heads, etc in my garage lab.  Oh, and a> couple of 10:1 probes I made out of board-edge SMA connectors, 450 ohm> (470 paralleled with 1.8k ohm) 0402 resistors, and 3-pin right-angle 0.1> inch spacing headers.  I've not completely characterized the probes, but> at least they pass up to about 12-13 GHz without much attenuation above> the expected 20 dB.  Planning to use them to probe some digital RF> boards I'm going to build for work (Raytheon).  Too much trouble to try> to get a fast enough sampling scope at work :(>> Enjoy the PPL app notes!  I've referred to AN-2a through -2e often.>> Thanks for the literature references.  I'll have to check them out> (someday).>> Jim Ford>>> ------ Original Message ------> From: "Reginald Beardsley via Groups.Io" <pulaskite=yahoo.com@groups.io>> To: TekScopes@groups.io> Sent: 3/14/2019 6:03:56 PM> Subject: Re: [TekScopes] Test input for an SD-32 sampling head>> >I have one  of Leo's 100 pS impulse units as a source for initial> experiments.  If I can narrow that to 10 -20 pS with discrete SMD parts I> may be able to get the idea to work.  There's a close connection to the> Hilbert operator hiding in there somewhere.> >> >I've been reading an excellent book on FPGA implementation of DSP by> Roger Woods et al most of the afternoon.  So I've not started on the> dissertation yet.  I can't really say much else until I understand the> mathematics and physics of using the reverse biased diodes as capacitors.> That should keep me entertained for a few weeks at least.> >> >In any case, failure doesn't matter.  It's a hobby project, not a client> deliverable.  I've been fascinated by the problem of getting a fast rise> time edge for a long time.  It's a bit of circular logic.  My excuse for> doing it is I bought an 11801 and my excuse for buying the 11801 is so I> could try to do it.  If I can narrow the 100 pS pulse by 5x I'll have an> excuse to buy an SD-32.> >> >I spent 3 years studying sparse L1 pursuits  using "A Mathematical> Introduction to Compressive Sensing" by Foucart and Rauhut as a text> followed by reading the original papers by Donoho, Candes et al.  Beats the> hell out of watching television.  I just wish I could find someone else who> was interested in the subject to discuss it with.  It's quite amazing what> you can do with sparse L1 pursuits and really easy to do in practice.> Understanding the math is not easy, but most people use FFTs without really> understanding them.> >> >Have Fun!> >Reg> >> >> >>> ---> This email has been checked for viruses by AVG.> https://www.avg.com>> >>

Re: 2467B No B Sweep

Siggi
 

On Tue, Mar 19, 2019 at 8:54 AM <thespin@...> wrote:

It’s not. The proper lights come on suggesting the scope is trying to run
the B sweep, but it isn’t running.
I would start by pulling, cleaning and re-seating U900. Second perhaps swap
U900 and U700.
If that doesn't help, you might be able to narrow this down a bit by
experimenting with various A/B sweep speed combos and B delay/trigger
settings. If there's any combo that will produce a sweep, then you can
start eliminating problems.
If there's no combo that'll start the sweep, then I'd focus on the constant
current generator op-amp (U910A in my 2467 schematic), and then on the
delay ref outputs from the A5 board.

Re: Test input for an SD-32 sampling head

Reginald Beardsley
 

Mark,

Thanks. I have to drive 150 miles round trip to access IEEE papers. I'll be collecting lots of NLTL papers the next time I go to Little Rock.

At the moment I'm working on deriving the equations for a transmission line with impedance steps designed to steepen the leading edge. Purely a passive linear pulse shaper using a coplanar waveguide with an air dielectric with no components if possible. After I have explored that I'll look into the magnitude of the improvement I can get using non-linear elements.

What I have in mind is a coplanar waveguide which starts with a 10 ohm impedance and then in a series of steps rises to 50 ohms. The concept is to apply a phase delay to the low frequencies which is greater than the delay applied to the high frequencies. My biggest concern at the moment is how to make the Q of the low frequency sections low enough to be physically tractable without resorting to coaxial cable.

Each step in impedance produces an infinite impulse response, so the mathematical notation can quickly get out of hand.

I have copied all the stuff from KH4HTV's website and read through most of it. Very nice stuff.

Leo Bodnar uses a Maxim 3949 LED driver in his pulsers. That is specified as 22 ps typical, 36 ps maximum Tr & Tf. That's already quite fast.

A fascinating aspect of this is that the mathematics are closely related to the normal incidence plane wave response of a layered medium in reflection seismology, the design of anti-reflection coatings in optics and to ultra wideband antenna design.


Have Fun!
Reg

TDS2024 display backing plate screw ID?

G Hopper
 

I suppose it might be possible to ask a more obscure question, but this
really is a long shot.

Does anyone have any information on the size of screws used on the aluminum
backing plate for the screen of a TDS2024 display?

It's a sub assembly so in the Tektronix diagrams, the screw details are not
called out in the service manual.

I managed to get the aforementioned TDS2024, but not before someone pulled
it apart and salvaged several things off this scope. Among the missing
items were/are several knobs, the CCFL tube, and the missing screws. Well,
other screws are missing too. Someone got what they needed and just threw
it back together good enough to make it look ok.

The screws are tiny. I think they are smaller than M4, but I can't be 100%
sure since I'm unable to find taps that small to identify the size and
thread pitch. I'm reluctant to try random screws as it looks pretty fragile
and I don't want to cross thread.

I was going to see if I can find another TDS10xx or 20xx scope to remove
and measure one of the screws, but I'm hoping that someone here might have
an idea since getting someone to let me disassemble his/her scope for a
screw size is a long-shot too.

Thanks in advance.

Grant Hopper

Re: 2467B No B Sweep

thespin@...
 

I've tried cleaning U500 and U900 to no avail, and then I swapped U900 and U700 again to no avail. Will continue searching for sweeps that might work and looking at that opamp.

On Tue, Mar 19, 2019 at 01:15 PM, Siggi wrote:


On Tue, Mar 19, 2019 at 8:54 AM <thespin@...> wrote:

It’s not. The proper lights come on suggesting the scope is trying to run
the B sweep, but it isn’t running.
I would start by pulling, cleaning and re-seating U900. Second perhaps swap
U900 and U700.
If that doesn't help, you might be able to narrow this down a bit by
experimenting with various A/B sweep speed combos and B delay/trigger
settings. If there's any combo that will produce a sweep, then you can
start eliminating problems.
If there's no combo that'll start the sweep, then I'd focus on the constant
current generator op-amp (U910A in my 2467 schematic), and then on the
delay ref outputs from the A5 board.

Re: 2467B No B Sweep

Siggi
 

Incidentally, it may help to understand what's inside the hybrid. If you're
wondering, take a look at page 6-59 of this document <
http://w140.com/tek_made_sm.pdf>. There's a fair bit of "stuff" in there
(that I haven't studied in detail).

On Tue, Mar 19, 2019 at 7:20 PM <thespin@...> wrote:

I've tried cleaning U500 and U900 to no avail, and then I swapped U900 and
U700 again to no avail. Will continue searching for sweeps that might work
and looking at that opamp.

On Tue, Mar 19, 2019 at 01:15 PM, Siggi wrote:


On Tue, Mar 19, 2019 at 8:54 AM <thespin@...> wrote:

It’s not. The proper lights come on suggesting the scope is trying to
run
the B sweep, but it isn’t running.
I would start by pulling, cleaning and re-seating U900. Second perhaps
swap
U900 and U700.
If that doesn't help, you might be able to narrow this down a bit by
experimenting with various A/B sweep speed combos and B delay/trigger
settings. If there's any combo that will produce a sweep, then you can
start eliminating problems.
If there's no combo that'll start the sweep, then I'd focus on the
constant
current generator op-amp (U910A in my 2467 schematic), and then on the
delay ref outputs from the A5 board.


Re: 2467B No B Sweep

Siggi
 

On Tue, Mar 19, 2019 at 7:20 PM <thespin@...> wrote:

I've tried cleaning U500 and U900 to no avail, and then I swapped U900 and
U700 again to no avail.
It's probably worth mentioning that unless you're planning on
re-calibrating the scope, you'll want to swap the sweep hybrids back. Part
of the calibration is to compensate for R/C on-hybrid component variances.

Re: 2467B No B Sweep

thespin@...
 

1. No sweeps seem to work
2. The opamp outputs look close enough that I'm inclined to assume they're doing their job
3. THO on U900 appears stuck high for all front panel configurations I could test. It dips low momentarily when turning the sec/div knob, but shows no periodic behavior.

On Tue, Mar 19, 2019 at 07:20 PM, <thespin@...> wrote:


I've tried cleaning U500 and U900 to no avail, and then I swapped U900 and
U700 again to no avail. Will continue searching for sweeps that might work and
looking at that opamp.

On Tue, Mar 19, 2019 at 01:15 PM, Siggi wrote:


On Tue, Mar 19, 2019 at 8:54 AM <thespin@...> wrote:

It’s not. The proper lights come on suggesting the scope is trying to
run
the B sweep, but it isn’t running.
I would start by pulling, cleaning and re-seating U900. Second perhaps swap
U900 and U700.
If that doesn't help, you might be able to narrow this down a bit by
experimenting with various A/B sweep speed combos and B delay/trigger
settings. If there's any combo that will produce a sweep, then you can
start eliminating problems.
If there's no combo that'll start the sweep, then I'd focus on the constant
current generator op-amp (U910A in my 2467 schematic), and then on the
delay ref outputs from the A5 board.

Re: 475 with no Display and no HV

SuddenLink
 

I installed the NTE539 voltage multiplier module this evening. The output of T1320 was connected to the input lug of the V multiplier module, and the LOW lug to ground. The FOCUS lug was clipped off and covered with silicon seal. Reinstalled the vertical preamp board and fired up the scope. Nothing. No high voltage.

I get a train of 500 mv pulses at about 22Khz at TP1318 but that’s it.

Back to the drawing board.

Ripley

Sent from Mail for Windows 10

From: SuddenLink
Sent: Sunday, March 17, 2019 8:28 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 475 with no Display and no HV

Hi Reed,

I received the NTE539 a few days ago and pulled out the existing HV trippler these evening. It is going to be a tight fit but it looks I can squeeze the new trippler in it’s place. The question is, what do I do with the Focus tab on the NTE539. I am thinking that it gets clipped off and covered with a glob of silicon seal.

I am going to hold off until I hear back from you.

Thank you.

Ripley

Sent from Mail for Windows 10

From: Reed Dickinson
Sent: Tuesday, March 5, 2019 3:11 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 475 with no Display and no HV

Hi:
See answers in red below.
On Tuesday, March 5, 2019, 11:55:54 AM PST, Jim Olson <v_12eng@...> wrote:

I'm curious where the Museum is located it sounds interesting to me too I'm in the SF bay area.

Jim O

On March 5, 2019 at 4:55 AM SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:


    Hi Reed,

    Yes sir working at the Radio Museum is a lot of fun and hard work at the same time but now that I am retired it is a great place to volunteer a few days a week.

    Between the NTE539 and NTE538 which one would you recommend for the Tektronix 475?
The NTE539 is the most suitable but if you get a 538 you need to connect the D lead to the LOW wire and connect both to ground.  Using the 539 connect LOW to ground, leave the FOCUS terminal open and connect the cap from the transformer to the IN terminal,  Either the 538 or the 539 MUST have a ,01uF, 5KV or 10KV cap between the transformer and the IN terminal.  NOt installing the cap will fry the multiplier in seconds.
Reed

    Ripley

    The words are mine but this iPad does what it will with them.

        > > On Mar 5, 2019, at 12:08 AM, Reed Dickinson <reed714@... mailto:reed714@... > wrote:

        Hi Ripley:
        Wiring in a NTE538 is a little different than wiring in an NTE539. When you get your 3Xer write ma back and I will detail how to do it.
        Your antique radio setup sounds most interesting. I would probably be helping you out at that facility if it were on the left coast.
        Reed
        On Monday, March 4, 2019, 4:43:02 PM PST, SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:

        Hello Reed,

        You just have been reading my mind. I was wondering how to handle the HV lead out to the CRT. What about the Focus Tap on the module. I am guessing that is left unterminated and highly insulated from anything around it.

        Our plan is to repair the scope so that we can sell it. The Museum of Radio and Technology is a nonprofit all volunteer organization. We don’t charge for admission so our revenue sources are from cash donations, sales from our gift shop , small grants, and the three swap meet/auctions that we host every year.

        Museum of Radio and Technology

        I will keep everyone posted as I bring this repair to completion.

        Ripley

        Sent from Mail for Windows 10

        From: Reed Dickinson
        Sent: Monday, March 4, 2019 4:59 PM
        To: TekScopes@groups.io mailto:TekScopes@groups.io
        Subject: Re: [TekScopes] 475 with no Display and no HV

        Hi Ripley:
        Good show, a new 3X voltage multiplier will get your 475 back on the air. If you elect to get an ECG or NTS 538 or 539 you will have to splice the HV lead leaving the new tripler. I very carefully slip a piece of thick wall plastic tubing over where the splice will be, carefully solder the joint leaving NO sharp points, coat the entire joint with silicone and slip the tubing over the joint. I put a small tie wrap over each end to keep moisture out. The 538 or 539 will fit in the space the present tripler is in, you will need to drill two mounting holes for the retainer screws.
        Reed Dickinson
        On Monday, March 4, 2019, 1:40:15 PM PST, SuddenLink <bob.ripley@... mailto:bob.ripley@... > wrote:

        Hi Reed,

        Per your suggestion I disconnected the wire from the secondary of T1320 to the voltage tripler and powered up the scope. The waveform at TP1318 immediately snapped to 32 volts p-p at about 70Khz without any persuasion via the 1K resistor trick. I also checked the oscillator over at the junction of CR1329 an C1326. It measures 320 volts p-p so it looks like I need to order a voltage tripler module.

        Thank you so much for your help. Obviously, you know your way around these scopes.

        Ripley

        Sent from Mail for Windows 10

        From: SuddenLink
        Sent: Sunday, March 3, 2019 8:27 PM
        To: TekScopes@groups.io mailto:TekScopes@groups.io
        Subject: Re: [TekScopes] 475 with no Display and no HV

        Hello Again,

        I went back to the circuit around Q1306 and Q1308 this evening. The resistors are all within specs. C1305 was pulled and checked. It is also fine. C1304 is good and so is C1302.
        By the way I am checking the capacitors with a DE-5000 LCR meter. It was never let me down yet.

        The only component that I have not replaced or substituted is Q1306. It checks fine on my little Chinse component tester. For whatever that is worth.

        Enough for today.

        Ripley

        Sent from Mail for Windows 10

        From: Steph L
        Sent: Sunday, March 3, 2019 7:05 PM
        To: TekScopes@groups.io mailto:TekScopes@groups.io
        Subject: Re: [TekScopes] 475 with no Display and no HV

        Hi Ripley,
        How about C1305 0.1uF.
        If open, gain of Q1306 (and whole oscillator loop) will be lower and perhaps not enough to maintain oscillation? (Great suggestion from Don re 1K pull up touch on Q1318 base.)
        Steph

        PS. Still nubie here and unsure which "Reply" button to click on. I clicked on Ripley's "what the heck?" message "reply" button and see it has been inserted a few messages prior! That is really confusing. I'm in Melbourne Oz GMT +10 hrs. Is this the reason (i mean time difference guys and not quirky)


















    >



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Museum of Radio and Technology

The Museum of Radio and Technology is one of the largest antique radio museums in the United States. See vintage...
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Re: 475 with no Display and no HV


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Re: Test input for an SD-32 sampling head

Jim Ford
 

Yes, the math is the same no matter whether it's coplanar waveguide,
seismology, anti-reflection coatings, UWB antennas, or dozens of other
applications. A wave is a wave. About 8 years ago I gave a
presentation on fiber optics to my RF and microwave colleagues. I
explained that fiber is just a roughly 200 terahertz circular dielectric
waveguide. And the quarter wavelength thick anti-reflection coatings on
the facets of a semiconductor optical amplifier operate in the same way
as quarter wave matching transformers at RF or microwave frequencies.

My personal preference is to do engineering for a living but stay close
to the physics and math. Sounds like you're the same way, Reg.

Jim

------ Original Message ------
From: "Reginald Beardsley via Groups.Io" <pulaskite=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: 3/19/2019 11:06:09 AM
Subject: Re: [TekScopes] Test input for an SD-32 sampling head

Mark,

Thanks. I have to drive 150 miles round trip to access IEEE papers. I'll be collecting lots of NLTL papers the next time I go to Little Rock.

At the moment I'm working on deriving the equations for a transmission line with impedance steps designed to steepen the leading edge. Purely a passive linear pulse shaper using a coplanar waveguide with an air dielectric with no components if possible. After I have explored that I'll look into the magnitude of the improvement I can get using non-linear elements.

What I have in mind is a coplanar waveguide which starts with a 10 ohm impedance and then in a series of steps rises to 50 ohms. The concept is to apply a phase delay to the low frequencies which is greater than the delay applied to the high frequencies. My biggest concern at the moment is how to make the Q of the low frequency sections low enough to be physically tractable without resorting to coaxial cable.

Each step in impedance produces an infinite impulse response, so the mathematical notation can quickly get out of hand.

I have copied all the stuff from KH4HTV's website and read through most of it. Very nice stuff.

Leo Bodnar uses a Maxim 3949 LED driver in his pulsers. That is specified as 22 ps typical, 36 ps maximum Tr & Tf. That's already quite fast.

A fascinating aspect of this is that the mathematics are closely related to the normal incidence plane wave response of a layered medium in reflection seismology, the design of anti-reflection coatings in optics and to ultra wideband antenna design.


Have Fun!
Reg



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