On Thu, Nov 12, 2020 at 3:28 PM Rogerio O <rodd414@gmail.com> wrote:

However any of the outputs seems to vary with time and all the voltages
are equal or lower than 120mV.

How are you probing this? Note that a 1X probe will load the outputs with
1MOhm, which is probably going to make them droop severely between
refreshes.
If you use a 10X probe, you'll load the outputs with 10MOhm, which is still
going to make them droop.
What you should see, however, is that each output should periodically "pop"
to one particular voltage level of the input, and then you'll probably see
them droop down (or up) to your ground level from there in that typical RC
discharging waveform.

Hello - I need 2 of the Option 13 RS232/Centronics interface boards/cables/ports for a TDS510a and TDS640a (they're the same part for both scopes). I am not looking to pay fleabay prices for them, as I am a hobbyist and mostly just want them to make these 2 scopes as "complete" as possible. If they are *very* cheap then I may be interested in 4 (to make dedicated "debug" interfaces for these scopes).

On Thu, Nov 12, 2020 at 09:19 PM, gifsim wrote:

I wish I had a TDR !!
I put some photos with a test (@ 800 mhz +0 dBm) just for fun
the strange thing is that even if I invert the two bnc of the coupler the
tracks do not move (always first the white track and then the green)
I didn't understand this thing .......

You're triggering on CH1, the white trace. If swapping the split-cable plugs between CH1 and CH2 results in the same image, i.e. CH1 the same amount before CH2, it means:
1. The cable's signal lengths for both plugs are about equal
2. What you're seeing is the delay between both channels in the 'scope and that's exactly what the cable is for, when adjusting the 'scope! The difference is about 40 ps.

Raymond

Siggi,
I don't think I am doing this right.
I can see a complex waveform at the input of the MUXes with a peak to peak voltage around 2.52V
However any of the outputs seems to vary with time and all the voltages are equal or lower than 120mV.
I can see that there are capacitors connected to ground at each of the MUX outlets.
Are they capable of smoothing the output signal so much that they like a DC voltage?
Roger

hello ed
I wish I had a TDR !!
I put some photos with a test (@ 800 mhz +0 dBm) just for fun
the strange thing is that even if I invert the two bnc of the coupler the tracks do not move (always first the white track and then the green)
I didn't understand this thing .......

https://groups.io/g/TekScopes/album?id=256551

On Thu, Nov 12, 2020 at 2:35 PM Rogerio O <rodd414@gmail.com> wrote:

Thanks Siggi for following this repair attempt.

Would you please comment if the values I have reported are really low?

Did you see this message https://groups.io/g/TekScopes/message/173180? It

feels like roughly every other message is getting lost here?

Meanwhile I will follow your suggestion to probe the MUXes.

I'd go through the DAC's reference network first, if I were you.

They are as you said 4051's.
To do that I have tackled a wire to the low end of R2521 so I have the
signal from the DAC.
I will then touch the outputs with another probe and see if they follow
the input at some part of the signal.
I don't know if I will manage to adjust the scope triggering and be able
to show the two signals.

You can twiddle the pots on the scope until one of the peaks is way above
all the others, that makes it easier to trigger on.

I have to put my one-cent-worth in here. I'd vote for the simplest suggestion of using a BNC Tee with "identical" cables connected, out to the DUT. If you really want to build something "permanent" or dedicated, it should be easy to do, with a small enclosure like a Pomona box, or just soldering the leads all together in a neat splice that can be tape-wrapped or heat-shrinked up, and even foil-wrapped if shielding is desired. To make cables with BNC at one end and wires to solder at the other, get a single high grade BNC-BNC cable assembly a little over twice the length needed, and cut it at the center. The final matching can be trimmed as close as you want and can measure (even TDR if capable), and you'll know that both pieces are the exact same kind of cable.

Ed

Bill,
Really nice scans. Thank you for sharing.
George

Thx. I didn't do any of the scans, everything is stuff I found here and there and then reworked in Photoshop.
The CRT collections were in decent shape but the 7K-series plug-in and the primer of waveforms took hours to panelbeat into shape.

Worth it though.

Everything is OCR'd and bookmarked for easy navigation.

Best,
Bill

Thanks Siggi for following this repair attempt.

Would you please comment if the values I have reported are really low?

Meanwhile I will follow your suggestion to probe the MUXes.
They are as you said 4051's.
To do that I have tackled a wire to the low end of R2521 so I have the signal from the DAC.
I will then touch the outputs with another probe and see if they follow the input at some part of the signal.
I don't know if I will manage to adjust the scope triggering and be able to show the two signals.
Roger

On Thu, Nov 12, 2020 at 11:32 AM Rogerio O <rodd414@gmail.com> wrote:

After another careful inspection I found out that I have swapped R2011 and
R2014. Sorry for wasting your time with another silly mistake.

Don't sweat it, nobody's wasting any time, we do this because we enjoy it.
When you mess up and have to backtrack, that's part of the learning
experience too. He who never made a mistake never did a damn thing in the
first place.

Bill,

Really nice scans. Thank you for sharing.

George

yes colin ...... building it as tek is almost impossible ... very very precise ...
however, you can have fun getting close to their accuracy

https://groups.io/g/TekScopes/photo/256562/0?p=Created,,,20,2,0,0

The 7L5 looks interesting, but the shipping to the UK is eye-watering. I realise that it isn't your decision, but $537-plus - ouch!
Colin.

Sorry, I made an error in deleting some text. It should read:

"a BNC tee-piece with three female connectors, plus two equal lengths of BNC male to BNC male coax could be used."

Colin.

I have two of these (none for sale!). The tricky bit in "building" one would be in sourcing the "joint" which has a female BNC and the two identical coax wires going to the two male BNCs. Of course, if you are talking about something similar which will do the job, then a BNC tee-piece with one three female connectors, plus two equal lengths of BNC male to BNC male coax could be used.
Colin.

On Thu, Nov 12, 2020 at 11:32 AM Rogerio O <rodd414@gmail.com> wrote:

Hi folks,
I think I have posted my previous reply on the wrong post again, since I
can't find it here. Sorry for that.
Here are my findings.
After another careful inspection I found out that I have swapped R2011 and
R2014. Sorry for wasting your time with another silly mistake.
The negative and positive references are now -1.15V and +1.22V (probably
low).

Yup, they're low.

The voltage drop around R2016 is 1.032V so the current through it is about
1mA.
Since the voltage drop across R2012 is very close to zero, it is
reasonable to assume that this current is going to the DAC and it is the
expected value for it (see Siggi's reply).
The voltages at the DAC output have a ppk value of 2.52V on both outputs.

This is low by roughly the same ratio as your references above.

Siggi, on another post mentioned that they should be close to 2*1.36V =
2.72V (this is again low, but I can't say for sure).
I am hoping that these readings mean that the DAC is working properly but
I have no experience to say so.
But there is something wrong with this circuit since it is impossible to
finish the DAC calibration procedure successfully.
When delta is pressed and the cursor is moved to the left, the minimum
negative voltage that I can get is -0.98V and the maximum is +1.24V.
The trimpot adjustment is already fully CCW so no further adjustment is
possible.
My next attempt will be to replace U2420, but I wouldn't like to start
changing components at random.
Any suggestios?

Measure the voltage drops over all the resistors in the DACs network. If
you find one has zero voltage drop, there's your problem (though R2012
should be roughly zero).
I believe the error you have would roughly correspond to R2015's current
contribution, but I'm too lazy to math at the moment.

thanks eric of the info

I figured it had to be like this
but when in doubt I asked the fantastic group
I have attached link to a photo
can it be built like this?

https://groups.io/g/TekScopes/photo/256551/0?p=Created,,,20,2,0,0

Guys:
Here's a bunch of Tek' lit I've lately reworked, noting that I've posted this to several lists.

The Cathode-ray Tube, 330pgs:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/Tektronix_Lit/The_Cathode_Ray_Tube.pdf

Tek CRT History:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/Tektronix_Lit/Textronix_CRT_History.pdf

Tek_7K_Series_Digital_Plug-In_Applications:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/Tektronix_Lit/Tek_7K_Series_Digital_Plug-In_Applications.pdf

A_Primer_of_Waveforms_and_Their_Oscilloscope_Displays:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/Tektronix_Lit/A_Primer_of_Waveforms_and_Their_Oscilloscope_Displays.pdf

Best,
Bill Perkins

On 2020-11-12 10:44 a.m., Glydeck via groups.io wrote:

If this is the item you’re looking at it’s not GPIB.
eBay item number:254572007620




https://www.ebay.com/itm/Inmac-050121-GPIB-to-Printer-parallel-adaptor-NEW-Spare/254572007620?hash=item3b45ac90c4:g:P-sAAOSwp2hemdOo

GPIB is a 24 pin device. That connector is 36 pin (Centronics). Also, not a great feedback rating.

The HC100 already has a parallel printer port.

To Jack: I am specifically looking for the GPIB card.

Thanks
--Toby

George

On Nov 10, 2020, at 9:56 AM, Jack2015 <sujack1950@gmail.com> wrote:

Hi Toby,

Are you looking for a GPIB to Printer adapter?
if yes,there is one on ebay. search "gpib to printer".

Jack

Hi folks,
I think I have posted my previous reply on the wrong post again, since I can't find it here. Sorry for that.
Here are my findings.
After another careful inspection I found out that I have swapped R2011 and R2014. Sorry for wasting your time with another silly mistake.
The negative and positive references are now -1.15V and +1.22V (probably low).
The voltage drop around R2016 is 1.032V so the current through it is about 1mA.
Since the voltage drop across R2012 is very close to zero, it is reasonable to assume that this current is going to the DAC and it is the expected value for it (see Siggi's reply).
The voltages at the DAC output have a ppk value of 2.52V on both outputs.
Siggi, on another post mentioned that they should be close to 2*1.36V = 2.72V (this is again low, but I can't say for sure).
I am hoping that these readings mean that the DAC is working properly but I have no experience to say so.
But there is something wrong with this circuit since it is impossible to finish the DAC calibration procedure successfully.
When delta is pressed and the cursor is moved to the left, the minimum negative voltage that I can get is -0.98V and the maximum is +1.24V.
The trimpot adjustment is already fully CCW so no further adjustment is possible.
My next attempt will be to replace U2420, but I wouldn't like to start changing components at random.
Any suggestios?
Roger