Which older digital scope - Page 1
Forum section: electronics / testgear

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: May 28, 2020, 04:12:22 pm
content: I'm going to pick up an older Tek scope and am waffling between The TDS 500/700 series and the TDS 5000/7000 series. My finger is currently on the TDS 784D button. So let's get the inevitable out of the way. What am I going to use it for? Since I'm really just asking for a general opinion I'm not sure that my use case is relevant. Nonetheless, high frequency observation up to potentially 1 GHz, rise times approaching ps range, single event capture, possible waveform analysis, etc. Four channel with full attenuators on each channel and color display with remote monitor option are a must. Don't need logging, programming, remote connections, crazy triggering scenarios, etc. Otherwise, general hobby use.

author: Elasia
author_rank: Frequent Contributor
timestamp: May 28, 2020, 05:29:54 pm
content: Really just down to how much you want to spend it sounds likeOne is what.. half the cost of the otherish?

author: Gyro
author_rank: Super Contributor
timestamp: May 28, 2020, 05:42:06 pm
content: You need to be wary of SMD Electrolytics spilling their guts on the board and eating tracks on Tek DSOs (probably other too) of this sort of vintage. If it gets under the acquisition chips it becomes a real problem.

author: nctnico
author_rank: Super Contributor
timestamp: May 28, 2020, 06:02:09 pm
content: The electrolytics leaking is a problem in the early TDS500/600/700 models from the early 90's. AFAIK mostly the A models. The D is from much later. All in all the Tektronix TDS500/700 series scopes are a good choice for all-round use.The Agilent 54835A / 54845A (VIN #33) is also interesting if short memory and no peak detect are not an issue (IOW: purely for HF work). Otherwise there are also many Lecroy oscilloscopes out there (but again no peak-detect).

author: Gyro
author_rank: Super Contributor
timestamp: May 28, 2020, 06:09:19 pm
content: Thanks for clarifying, I remember seeing the boards and them being TDS500-700 series, but no more.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: May 28, 2020, 06:13:02 pm
content: Quote from: nctnico on May 28, 2020, 06:02:09 pmYea, I've heard the Cs and Ds are considered more reliable. Thanks.

author: nctnico
author_rank: Super Contributor
timestamp: May 28, 2020, 06:20:57 pm
content: But do realise that all of these older oscilloscopes have their daemons so it is important to buy a good one if you are not looking for a repair project. It takes some research into the common problems and their fixes in order to make a good assessment of the risks involved.For the Tektronix TDS500/600/700 series you need special equipment and software to do the calibration and the NVRAM + clock chip are weak points. Also the color display can fail at some point.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: May 28, 2020, 06:57:49 pm
content: Quote from: nctnico on May 28, 2020, 06:20:57 pmTo some extent I've repaired or at least calibrated nearly every instrument I own. Battling a blown up HP 3456 at the moment. I'm good with the risk. If calibration becomes too involved I send it off to the Tek cal lab just up the road from me.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: May 28, 2020, 11:39:35 pm
content: No alarm bells, so 784D on the way. Thanks for the responses.

author: rsjsouza
author_rank: Super Contributor
timestamp: May 29, 2020, 01:24:04 am
content: Beautiful lab, BTW!

author: snoopy
author_rank: Frequent Contributor
timestamp: May 29, 2020, 01:54:51 am
content: 5000/7000 is much better scope than 500/700 scopes if you can get one in good working orderThe 7000 is a much more modern scope and really only lacks serial decoding otherwise it's still a relevant scope today and can handle all of Tek's active probes with the TekProbe interface. Be careful of 7000 models above 1GHz such as 7154, 7254, 7404,7704 as they use Tek's funny Tek connect 50 ohm input and you need expensive adaptors just to use ordinary probesFailing that a good working TDS3000 scope is still a great scope to use and I would prefer it over the 700 series scopescheers

author: snoopy
author_rank: Frequent Contributor
timestamp: May 29, 2020, 02:00:04 am
content: Quote from: Ground_Loop on May 28, 2020, 11:39:35 pmI have a 784A and it's a nice scope but the D series was the first to have DPO. They will accept any of Tek's probes with the Tek Probe interfacecheersdavid

author: Electro Fan
author_rank: Super Contributor
timestamp: May 29, 2020, 02:24:24 am
content: Quote from: Ground_Loop on May 28, 2020, 06:57:49 pmOff topic, but Nicely organized bench/lab!

author: texaspyro
author_rank: Super Contributor
timestamp: May 30, 2020, 04:24:40 am
content: Quote from: snoopy on May 29, 2020, 01:54:51 amMe too... also they are very easy to upgrade bandwidth (f you have GPIB or serial port on it) and options...