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Which GPIB-USB adapter do you have and what operating system?

Vince - K8ZW.

--
K8ZW

Dear all,
I have bought a TDS784D at Ebay some time ago and had no time to test it.
When I finally had time to turn it on, I realized that the display is very faint and the image is out of focus.
The intensity adjustment available on the menu is already at 100%.
I found a very brief adjustment instruction in the service manual and I fumbled on the pots ( after taking a long time to find them) but they seem to be arranged in a different order than the one described on the manual.
There is a list of the appropriate voltages to the display module on the display troubleshooting section and all of them are ok.
I found one person on Ebay selling a new display module and he mentions that there is a time consuming adjustment procedure for this module, but I could not find it anywhere.
I have uploaded one photo of the menu screen to show how out of focus the display is (the file is TDS784D dim display).
My questions are:
1 - Where can I find a detailed adjustment procedure for the display module?
2 - Is there a way to check if the problem is the CRT being "exausted"?
3 - There is a company offering the NewScope-T1 Color LCD replacement Kit as a replacement. is this a good alternate in case I need to replace the CRT?

On Fri, Sep 25, 2020 at 05:31 PM, <tekscopegroup@...> wrote:

I also have a 2247A and I can can confirm that front covers are completely
different from other 22xx series ones, as would be the one for the 2252 which
uses the same as the 2247A. No stamped PN anywhere on that one that I could
find.

P/N 200-3232-00

Raymond

I had a very quick look around and it seems that upgrades on the TDS460A are enormously more complex than the 'type in two lines of GPIB commands' that works so well on the later models.

Best of luck,

Roger

On Thu, Sep 24, 2020 at 08:51 AM, Raymond Domp Frank wrote:

On Thu, Sep 24, 2020 at 05:47 PM, <tekscopegroup@...> wrote:

I just found that have among my notes that the front cover PN 200-2520-00

fits All 22xx models.

I mostly agree: I think that the same front cover fits all 2200 models, except
the 224X and 2252 models.

Raymond

I also have a 2247A and I can can confirm that front covers are completely different from other 22xx series ones, as would be the one for the 2252 which uses the same as the 2247A. No stamped PN anywhere on that one that I could find.

Hi Roger,
actually I have an USB based GPIB adapter, but without controlling Software to read/write I won't be able to do much. The only I GPIB SW I use with this is Pete Millet's package for the HP 8903 distortion analyzer. Embarking on a big DIY effort to figure out the commands etc.. not really in my skill set. That's why I was looking for "spare parts" approach of swapping chips.
Thanks
Paba

Anybody seen a ceramic bypass cap go bad?

Yes, but that was a very high leakage failure (almost a short) on a 7K series logic board.

I've known them to crack and fail open as well.

Anyone have some other cases to add?

David

OK here's some thoughts:

1) The -5V supply measured at [2] at the input to L68 should have about 100mV peak to peak saw-tooth ripple at about 50kHz which is before the output filtering network (see the voltage and waveform conditions page just prior to the schematic). So the ripple at TP92 should be LESS than 100mV. Were you measuring its output at TP92 or on one of the logic boards (if the latter you may be picking up digital hash).
2) I'd take a good look at the electrolytic caps on the auxiliary regulator board, especially C68, C84, C86 and C92. There are a couple more at the input but I don't think they will be the cause of problems. Also look for any suspect caps on the -5V rail on the logic boards

HtH David

An update:

My initial indication of a problem was glitches in the display, such as "_"
characters showing up on parts of the screen where they didn't belong.
These glitches were stored in video RAM and were thus visible until the
screen image in RAM was updated.
My guess for the most likely culprit was power supply noise, and indeed
there is a LOT of noise on the supplies, but it is not line noise. In fact,
it is nearly all switching noise from the digital circuitry. If I hold the
microcontrollers in reset, the supplies get very quiet. When the
microcontrollers are running, there is significant noise on all the
supplies:
-15V rail: 1.2Vpp
+5V rail: 1.1Vpp
+12V rail: 0.5Vpp
+15V rail: 0.7Vpp
The noise on each of the supplies is all the same noise (triggering on one
channel produces a solid lock on the others). It is asynchronous to the
14.xxx MHz pixel clock of the NS405, so I believe it is all from the 8032
(12 MHz XTAL). The lowest observable frequency in the noise is around 2 MHz
(only looking in the time domain at the moment).
I've isolated this down to just the main board; the CRT, front panel, and
collector supply are out of the picture.
The main board contains the 8032, NS405, base/gate drive circuit (DAC), and
emitter test circuit (ADC).
Supplies are all linear, using 78xx and 79xx regulators.
At this high of frequency, electrolytics aren't contributing much to the
bypass, right? Each rail only has 220uF after the regulator. I've checked
half of them, and while they've aged they aren't trash yet. Anybody seen a
ceramic bypass cap go bad?

Dave Casey


On Thu, Sep 24, 2020 at 1:11 AM Dave Casey via groups.io <polara413=
[email protected]> wrote:

I'm not so sure they are. DC leakage current is well below 100uA at 20V.
I'll check them again at 40.
When I say the cans are domed, they may have been made that way as these
are sealed at the bottom and don't have the usual "fault lines" in the
domed end.
I will also check ESR. Replacements are standing by, but I'm not convinced
these were the source of the noise, especially since it's not line noise.
These are all pre-regulator caps, so I'll check the smaller ones after the
linear regulators to see if anything is suspicious there. Low capacitance
on the output and some fast switching in the video circuits could be to
blame. I should also see if the noise is in sync with the video.

Dave Casey

On Wed, Sep 23, 2020 at 9:43 PM Richard R. Pope <mechanic_2@...>
wrote:

Dave,
Those electrolytics are defective. They have been running hot. Time
to replace them. I hope that this helps!
GOD Bless and Thanks,
rich!

On 9/23/2020 9:39 PM, Dave Casey wrote:

I spoke so highly of my 571 last month. When I recently went to use

it, I

was getting some artifacts in the display so I have set out to

investigate.

Unfortunately you can tell this wasn't designed in Beaverton because

you

have to remove the CRT to get the main board out. There are some large
Roedenstein electrolytics used for supply smoothing that have a bit of

a

dome to the end of them. Not sure if these were flat when new, but they
don't appear to be leaky (neither physically nor electrically). There

is

significant noise (100-200mVpp) on the supplies, but it's not line

ripple.

It appears to be around 2 MHz and is two similarly disruptive pulses

around

200ns out of phase.

In the process of disassembly, I have pulled and saved the three EPROM
images. Two run the 8032 controller, and one runs the NS405 "terminal

on

a

chip" that is used to draw the display and printer output.
I haven't exhaustively perused the images, but the graphics ROM has

some

ASCII easter eggs I noticed. After the usual Tektronix copyright

statement

is "Written by: Folkert ten Brummelhuis (started). Sjoerd J. Punter"

and

soon after "[Makke yn Frysl?n]" which is Frisian for "Made in

Friesland",

the province in which Heerenveen is situated. Later in the ROM the

phrase

"Joke Mirjam Esther" appears twice, about (but not exactly) 64 bytes

apart.

I believe these are three given names commonly used in the region,

perhaps

the names of those endeared to one or both programmers.

Dave Casey

On Fri, Aug 21, 2020 at 1:31 PM Dave Casey via groups.io <polara413=
[email protected]> wrote:

I stand corrected; can confirm, my S/N also starts with H. Thanks!

Dave Casey

On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:

On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:

Built by Sony-Tektronix.

No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H)

and

as

far as I remember it was also designed by them.

/H?kan

You can find USB to GPIB interfaces for sale or there are designs to make your own using Arduino compatible hardware and software.

For some of the other TDS series enabling options is just a matter of typing in two commands by hand.

Roger

IMHO,the operative words "but here?" express succinctly what many of us feel.

Best wishes to all,Brian g

Hello
I figure i can pop out my nvram chip and replace with a another that has the FFT option enabled.
Anyone sell these. If you have such chip in yours would you consider copying it and selling it to me.
The reason I ask it no Dos machines or nvram programmers or isa-gpib around here.

Thanks
Paba

I see it. Thank you. Very, very strange. Looks as though I will need to remove the 2 fuse holders, too, to remove the panel to access the nut holding the pot. Why in the world did Tek make that so complex and difficult? But I appreciate the assistance.

R

On Fri, Sep 25, 2020 at 02:08 AM, Richard P wrote:

I can’t say that I see a pot mounting nut on my old 453 unit. Where should I
look?

Remove the aluminum cover sideplate, mounted with two nuts accepting Allen screws (Astig and Trace Rotation) and the variable time/div knob.
Underneath, you'll find the nut holding the pot. It's mounted on a recessed part in the extrusion.

Raymond

Hello, John,

Thank you. I uploaded just now two photos...the front panel and the rear panel. I can’t say that I see a pot mounting nut on my old 453 unit. Where should I look?

Richard

Richard,
In the exploded mechanical drawing of the 453A manual there is a sub-panel behind the outer panel of the swing out section. The pot mounting nut is behind the outer panel. I assume the 453 is similar.
--John Gord

I am looking to replace a 20K pot/switch in my 453. It’s the variable on/off control for time/division, channel B, located on the side of the scope in a recessed panel. The panel swings out easily for servicing when the cabinet is removed. But I can’t figure out how the pot is mounted to the panel. Behind the knob there is...nothing. No typical retaining nut on the threaded shaft. How do I remove this pot? How is it mounted? Thanks.

Richard

Any ideas what could be causing all that ripple on the -5 line?

I did try to buy this item but after a signed contract and payment mostly silence.
Has anyone else paid for this item ? If so then this is a scam.
Please drop me a private message to confirm.

If not then this migth still be valid deal but something might have happened to 'Mark Yeager'.

Oh, the trigger pulse is a flat topped rectangular wave, looks clean both without and with the display section attached.