Hi all,
Thanks a lot for this thread!
Last year I bought a
TDS 744A as part of a test-equipment lot buying. It came with a couple P6139A probes, the pouch and, free of charge, lots of dirt
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
I had not done more than powering it up and some basic checks. It worked, but needed cleaning. My usual digital oscilloscope is a
DPO 3032, which is a 300MHz, 2.5Gs/s unit. So, except for the 500MHz bandwidth, the
TDS 744A was a lesser unit and I didn't find any use for it at the moment.
But testerday, while looking for other info on a different project (a Tektronix
CSA 8000 mainframe I am trying to get back to work), I stumbled upon this thread. Wow!!!. I was amazed to find I had a hidden treasure
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
, as my
744A came without 1M option... which seemed to be also a configuration hack (and, yes, I have managed to activate it using just Keysight IO libraries and GPIB
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
)
So I took it out its casing and carefully cleaned it, including the keypads, as some keys were not working fine. The HORIZONTAL POSITION control also failed, so I took out all the front panel, dismantled and cleaned it. Now the oscilloscope looks like a close to new unit! (I will put some pictures later)
Well, once I performed the resistor mod and the capacitor removal, yes, the unit is shown as a
784A and now it reaches 4 Gs/s. I have run the SPC after a warm up period, and it has also worked fine. But there is a problem when the unit works at 4 Gs/s, which I think it is a matter of calibration. The test is simple: I put a 250MHz signal and activate only Channel 1. What the unit shows is a distorted signal. Then, if I activate Channel 2, so the sampling rate lowers to 2 Gs/s, the signal is an almost perfect sinusoid.
I need to setup a PC with a NI GPIB card to run the calibration software which I hope will solve this problem.
Regards,
JOSE