Products > Test Equipment
Conversion of 500MHz TDS744A to 1GHz TDS784A
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Jay_Diddy_B:
Hi,

I managed to get the Tektronix field adjustment software to run in an automated manner.

I got some useful tips from this YouTube video:



This guy has some other similar videos, but he stops short of giving all the answers.

The Tektronix software is not all that friendly.

I found that it worked for me with the following equipment:

Hp3478A DMM
Analogic (Data precision) 8200 DC voltage standard
Fluke 6061A

You still have to move the cables around *a lot*

The software checks the high frequency cal for each channel in 20 MHz steps from 500MHz to 1 GHz if I remember correctly.

Some of the adventure is documented in this thread:

https://www.eevblog.com/forum/testgear/tektronix-tds700a-field-adjust-software-help-needed/msg563939/#msg563939


Regards,

Jay_Diddy_B
cncjerry:

--- Quote from: rx8pilot on August 11, 2016, 01:25:59 am ---I have been hoping to get my hands on one of these fast pulse generators. Designed by esteemed forum member based on the Jim Williams design but with some clever updates.

I would love to get a kit, or gerbers, or a built unit, whatever. Obviously you need a proper signal generator first to calibrate, but it could be used to see how the scope responds to a fast edge. Since it only samples at 2Gs/s - you are right at the Nyquist at 1Ghz where the front end starts to roll off.

--- End quote ---

After the upgrade the sample time is doubled to 4G.  There was also a way to enable the rest of the memory using software and a switch in the side. 
rx8pilot:
I had no idea the hardware could do that. Awesome.

Sent from my horrible mobile....

cncjerry:
The 784 scope is just a beast.  I have a 3054B as well and though it is loaded with features, when I need to stare at a signal, I use my upgraded 784.  It has a very, very crisp display no matter what the detractors say about the shutter.  The colors are rich, much more so than an LED display. I often wonder why these displays weren't advanced. It's clear to me that the LED display is inferior and is used to cut cost like a front wheel drive car; sold as better but really just a way to cut manufacturing costs.

One thing I have to dig into on mine, is it seems like my scope has a lot of noise on the probe compensation test points.  It could be just the local FM stations leaking through the probe cables.  Do you guys see that as well?  put it in envelope mode and probe the test points.

Thanks
timb:

--- Quote from: cncjerry on August 13, 2016, 12:59:27 am ---The 784 scope is just a beast.  I have a 3054B as well and though it is loaded with features, when I need to stare at a signal, I use my upgraded 784.  It has a very, very crisp display no matter what the detractors say about the shutter.  The colors are rich, much more so than an LED display. I often wonder why these displays weren't advanced. It's clear to me that the LED display is inferior and is used to cut cost like a front wheel drive car; sold as better but really just a way to cut manufacturing costs.

One thing I have to dig into on mine, is it seems like my scope has a lot of noise on the probe compensation test points.  It could be just the local FM stations leaking through the probe cables.  Do you guys see that as well?  put it in envelope mode and probe the test points.

Thanks

--- End quote ---

The probe calibrator on the TDS 5/7xx series is pretty crappy when compared to some of Tektronix's previous work (like the calibrator on the 2465 series, which automatically changes frequency from 100Hz to 5MHz, depending on what sweep rate you've got set; the output is semi-regulated and has very fast rise and fall times).

On these TDS scopes, the calibration signal is provided by the little MCU on the front panel (it monitors the pots and buttons and talks to the CPU over a serial interface). Basically, it's just programmed to waggle a GPIO at 1kHz, which is then amplified by a transistor.

It's powered by the 5V digital supply, if I remember right, so I'm sure that couples in significant noise. Hitting buttons or twirling knobs will also cause the signal to occasionally drop pulses.

Honestly, an RC oscillator or 555 timer would have been better than using the MCU, but for compensating probes I guess it does the job... (I always use the Fast Rise output of my PG 506 or my 2465B's output for probe compensation anyway, so it doesn't bother me much.)
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