Agilent Infiniium 54852A 2GHz 4CH 10GSa/s vs Tektronix TDS694C 3GHz 4CH 10GSa/s - Page 1
Forum section: electronics / testgear

author: LeoUCDavis
author_rank: Contributor
timestamp: September 23, 2014, 07:17:24 pm
content: Hi allI have a dead Agilent Infiniium 54852A 2GHz 4CH 10GSa/s oscilloscope that would require 3500USD to repair. On the other hand, I've found that I can purchase a Tektronix TDS694C 3GHz 4CH 10GSa/s for 2750USD (http://www.axiomtest.com/Oscilloscopes-used-refurbished-21/gt-1-GHz-to-lteq-4-GHz-used-refurbished-111/Tektronix-TDS694C-used-refurbished)What would you say? Should I repair the Agilent or just buy the Tek? I mostly need the scope to measure narrowband signal around 2.4 GHz.Thanks!

author: nctnico
author_rank: Super Contributor
timestamp: September 23, 2014, 07:46:38 pm
content: The TDS694C has a weak point: the trigger chip can be fried and that chip is unobtanium. Besides that $2570 is way too much for a TDS694C; it is old and obsolete.

author: LeoUCDavis
author_rank: Contributor
timestamp: September 23, 2014, 07:57:36 pm
content: Thanks for the quick reply. Do you have any recommendations for a decent oscilloscope for 2.4 GHz measurement? especially considering that I have less than $4k to spare?Quote from: nctnico on September 23, 2014, 07:46:38 pm

author: nctnico
author_rank: Super Contributor
timestamp: September 23, 2014, 08:04:40 pm
content: Good question. Why do you need an oscilloscope? Can't you use a spectrum analyser?

author: LeoUCDavis
author_rank: Contributor
timestamp: September 23, 2014, 08:06:54 pm
content: Because the customer wants to see the time-domain waveform...Quote from: nctnico on September 23, 2014, 08:04:40 pm

author: nctnico
author_rank: Super Contributor
timestamp: September 23, 2014, 09:25:19 pm
content: That is an expensive picture... What is the problem with the Agilent oscilloscope? Did you attempt to repair it yet?

author: LeoUCDavis
author_rank: Contributor
timestamp: September 23, 2014, 09:40:05 pm
content: No I don't have much experience with equipment repair. The scope doesn't acquire any signals. I had it examined by a local repair company. They say that some data acquisition board is faulty and had to be replaced by Agilent. Plus labor, it comes to ~$3500.The Agilent scope is a 2GHz bandwidth one so it doesn't quite meet the need, which is why I'm tempted by the Tek unit.Quote from: nctnico on September 23, 2014, 09:25:19 pm

author: eurofox
author_rank: Unknown
timestamp: September 23, 2014, 10:09:35 pm
content: Quote from: LeoUCDavis on September 23, 2014, 07:17:24 pmI got a TDS984C 1Ghz, great scope but small screen and old technology. I think it is not a good idea to invest so much money in technology that is 25 years old.I have now a DSOX-3001 and I don't want any other scope anymore.If the signal got the same pattern during acquisition maybe you could use a sampling scope that is cheaper.

author: nctnico
author_rank: Super Contributor
timestamp: September 23, 2014, 10:16:25 pm
content: Repairing equipment is much like debugging your own circuits. The biggest difference is that you are fixing someone else's mistakeAnyway 2GHz is indeed on the low side for what you want to measure. I wouldn't spend more than $2500 on a TDS694C though. Another option would be a TDS820 which is a 6GHz digitizing oscilloscope. If your signal is repetitive it should work. These sell for much less but can have problems with leaky capacitors if it is from before 1995 (the ones with the blue Tektronix logo are the oldest). Also the triggering only goes to 2GHz so 2.4GHz could mean pushing the limits.

author: eurofox
author_rank: Unknown
timestamp: September 23, 2014, 10:27:10 pm
content: Quote from: nctnico on September 23, 2014, 10:16:25 pmI got a latest TDS820 with no capacitors problem, it is a good scope for fast pulses but not for high frequency, the one I got (I sold it) trigger till 1,7Ghz but measure pulses up to sub ps.My little DS800 sampling USB scope trigger till 4,2GHz and with a prescaler above 11GHz.

author: nctnico
author_rank: Super Contributor
timestamp: September 23, 2014, 11:24:10 pm
content: Where did you get the DS800? It seems it could serve the OP.

author: eurofox
author_rank: Unknown
timestamp: September 23, 2014, 11:41:44 pm
content: Quote from: nctnico on September 23, 2014, 11:24:10 pmThe DS800 come from Darwin Sbanovic, he design it, assemble it on he's owns design pick and place machine, mill the front and back plate of the instrument.The weak part is the PC software that is written in VB, I already improve it but I'm not a VB expert, it should be ported to C but you can imagine that it is quite sophisticated.I can now manage to capture very short pulses from a few ps rising edge. I can attach some pictures if needed.

author: LeoUCDavis
author_rank: Contributor
timestamp: September 24, 2014, 12:15:48 am
content: the DS800E seems very interesting. I'll try to get one.I wish he could open source the design.Quote from: eurofox on September 23, 2014, 11:41:44 pm

author: ConKbot
author_rank: Super Contributor
timestamp: September 24, 2014, 02:09:32 am
content: Quote from: LeoUCDavis on September 23, 2014, 08:06:54 pmWhat is a 8bit (or even 12bit in hi-res?) scope waveform with a 1mv/div minimum sensitivity going to show you (besides time domain) that hooking it up to a spec and or signal analyzer with lots of dynamic range wont? Are you sure the customer knows what they really want? Is there a measurement they are interested in or is it really just a picture? Have you considered renting a scope that would do it? Not sure how much renting an older high end scope like that would cost.

author: LeoUCDavis
author_rank: Contributor
timestamp: September 24, 2014, 08:47:49 pm
content: Good questions.A bit more details on what we are looking at. So we have a pulsed oscillator working around 2.4 GHz. The pulse duration is about 20ns. We'd like to observe the start up waveform of the oscillator.The oscillation of the oscillator is not coherent from pulse to pulse, so I would assume that a sample scope won't work very well in this case.Quote from: ConKbot on September 24, 2014, 02:09:32 am

author: nctnico
author_rank: Super Contributor
timestamp: September 24, 2014, 10:09:14 pm
content: That sounds like you need a realtime sampling oscilloscope indeed.

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 25, 2014, 06:30:13 pm
content: Quote from: LeoUCDavis on September 24, 2014, 08:47:49 pmI have a 4 GHz 20 GSa/sec 54854A with the long memory option. I could take some measurements of the device for you if you can ship it.

author: LeoUCDavis
author_rank: Contributor
timestamp: September 25, 2014, 07:12:50 pm
content: Thanks Alex for offering to help. But we are really looking for a scope that we could use almost everyday to characterize our circuit as we keep improving it. How much would a scope like yours cost?Quote from: alex.forencich on September 25, 2014, 06:30:13 pm

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 25, 2014, 07:24:51 pm
content: Quote from: LeoUCDavis on September 25, 2014, 07:12:50 pmI paid about $4k for it, but it was sold for parts as it did not boot up. I was expecting a wiped hard drive as it was from a defense contractor, but it turns out there was a blown fuse in the hard drive caddy so I was able to salvage the calibration and license data. Most of the >= 4 GHz infiniium scopes that I have seen on ebay are priced at least twice that, or they have major problems with the acquisition board.

author: LeoUCDavis
author_rank: Contributor
timestamp: September 25, 2014, 10:51:51 pm
content: Sounds like a sweet deal!Quote from: alex.forencich on September 25, 2014, 07:24:51 pm

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: September 28, 2014, 09:02:39 am
content: Quote from: LeoUCDavis on September 25, 2014, 10:51:51 pmIf you have some patience then for a bit over $4k you can get something like this:http://www.ebay.com/itm/LECROY-WAVEPRO-7300A-3GHz-QUAD-20GS-s-DIGITAL-STORAGE-OSCILLOSCOPE-/231333585982?nma=true&si=5rLy33FDCWcPbq9gCK1JRebq9pI%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557Only 3GHz bandwidth of course but then it's fully functional and does seem to have all options.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 28, 2014, 10:13:04 am
content: Quote from: LeoUCDavis on September 23, 2014, 07:17:24 pmDon't forget that even a faulty high-spec scope will have some significant resale value, which may fund some additional budgetQuoteJust because a board is faulty doesn't mean it needs to be replaced- It would probably worth spending a bit of time on it.

author: Lunasix
author_rank: Regular Contributor
timestamp: September 28, 2014, 11:00:44 am
content: I remember the case of a Tek 7xx (or 6xx, long time ago), around year 2004, with a failure, and Tektronix answered : no more spare parts !As Tektronix is generous, they "offered" 500$ for it if we buy a new one