"Passes Self Test" - Page 1
Forum section: electronics / general

author: Jwalling
author_rank: Unknown
timestamp: August 14, 2017, 02:14:15 pm
content: http://www.ebay.com/itm/SONY-Tektronix-AWG2020-Arbitrary-Wavelength-Generator-OPTION-03-/142476129242?epid=1123834323&hash=item212c3d33da:g:TscAAOSwLgtZkaz8

author: Asmyldof
author_rank: Regular Contributor
timestamp: August 14, 2017, 03:43:38 pm
content: On the other hand you could buy this one:http://www.ebay.com/itm/Tektronix-Sony-AWG2020-AWG-2020-Arbitrary-Waveform-Generator/382143492526?rt=nc&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D45562%26meid%3D29a26e30d9d143e0ba5d49d48a58a979%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D142476129242&_trksid=p2047675.c100005.m1851In stead of the similarly priced brand new R&S AWG with 1.1GHz installed (SMC100A + SMC-B101 direct from the R&S webshop)Edit: My bad, that's obviously not an AWG. Still though.

author: Brumby
author_rank: Unknown
timestamp: August 14, 2017, 04:12:31 pm
content: Graded on a curve, no doubt.Four PASS, two "No result" and one FAIL. That gets it over the line ....surely?

author: Asmyldof
author_rank: Regular Contributor
timestamp: August 14, 2017, 04:40:59 pm
content: What do you even need a clock for in a device like that?

author: Berni
author_rank: Super Contributor
timestamp: August 14, 2017, 04:58:07 pm
content: I scored a Tek AWG2041 on a ebay auction not long ago (Sorry if i was bidding against you on it).But then when i power it up, it starts failing the selftest on the clock board, that got me a bit worried since this thing has its fair share of unobtainium ASICs. Rebooting doesn't help, unplugging it for a few minutes doesn't help, factory reset doesn't help. So seeing its surely a hardware issue i take the lid off and its quite nicely done inside. Following the rule of do the easy thing first, i go about re-seating the problematic card in the back plane in case it had a bad contact on it. So to get it out i start unplugging the coax cables that run to it. I have never seen this type of connector before so i try randomly pulling and wiggling it until it pops out. They are a style of connector similar to cable tv F connectors where the connector is only the shield part while the stripped center conductor in the coax cable is used as the pin, except that these are much smaller and have no thread. Since the center conductor is bare copper it naturally accumulated a nice dark layer of oxide over all these years. Seeing this i decided to instead just clean the center pin on all the cables leading to the clock board by giving them a scrape and pluging everything back in. Give it power again, turn it on and wohoo! Passes self test and generates waveforms as it should with frequency and amplitude spot on. Lovely jovleyI have attached some photos of its insides since it does look pretty interesting. It has taken them quite a lot of electronics to reach 1GS/s back in the 90s.(Photos are all taken of the sides, haven't pulled out any cards for photos)But be aware that this wave gen has some limitations. The 2nd channel is not actually a 2nd channel, all it can do is be 0V or inverse of channel 1. Also the standard sine square ramp etc... waveforms only go up to 10MHz on the AWG2041, yet the analog front end of it actually has about 150MHz of bandwidth. This lets you create perfectly nice sine waves all the way up to 150MHz by using its arb mode and loading in a sinewave sample(Way more button pushing). But on the upside it does have a very flexible custom waveform editor built in, has lots of flexible auxiliary ports for trigger, markers, gating and can assemble together very long complex sequences from chunks of data(Useful if you have the 8bit digital output bus option on the back)EDIT:Why do you need a clock?The "clock" self test refers to the clock board that generates the sampling clock for the DAC. In the AWG2041 this is a fractional PLL synthesizer that can generate anything from 5Hz to 1Ghz with 6 digits of resolution. So if this fails this self test it means there will likely be no output waveform at all or it will be at the wrong frequency.

author: Asmyldof
author_rank: Regular Contributor
timestamp: August 14, 2017, 05:32:37 pm
content: Re: "Why clock": I think your sarcasm detector is on the fritz a bit.Re: "Repairs": It's great you managed to fix it, of course and I shall not say anything negative on that subject (nor will I say "great job", as this may accidentally unintentionally trigger your sarcasm parser), but that doesn't mean that: 1. this one has the same problem, or that it is the only one it has, nor: 2. That this thing is passing the self-test as advertised.Nor is comparable quality and stability newly bought expensive enough to even have a base cost for such a cumbersome beast had it actually passed them, but with no other verification to current accuracy, stability and capability done.

author: Berni
author_rank: Super Contributor
timestamp: August 14, 2017, 06:04:17 pm
content: Sorry that i didn't pick that up. But these old Tek AWGs are not that bad if you can get them for a good price as brand new arb signal generators with similar specs can still cost quite a bit(Well okay the AWG2020 is a bit more pedestrian with only 250MS/s, but there are faster ones in the range).Obviously it was not the most difficult thing to fix, but most of the broken gear that i ended up with here had simple fixes. Some as simple as putting in a fuse. Occasionally i end up hunting for a blown opamp but thats about it. At least the fix is not as janky as the repair i did on my Gigatroonics 8GHz RF synthesizer where i ended up taking apart the relay switched attenuator module and gluing a little piece of paper under one of the solenoids to act as a spacer and prevent it getting stuck in the end position. Crude fix but the frequency response was still ruler flat all the way to 8GHz and that relay is still switching fine to this day and cost me nothing but my time and effort.

author: Jwalling
author_rank: Unknown
timestamp: August 14, 2017, 09:23:35 pm
content: IMAG0832.jpgAre those Brooktree? I'm assuming those are the DACs.https://en.wikipedia.org/wiki/BrooktreeBarely a mention.

author: bitseeker
author_rank: Super Contributor
timestamp: August 14, 2017, 10:12:24 pm
content: Also humorous is the "arbitrarywavelengthgenerator", although technically true.

author: Brumby
author_rank: Unknown
timestamp: August 15, 2017, 02:36:50 am
content: Quote from: bitseeker on August 14, 2017, 10:12:24 pmYou are being technically polite.To me, it smacks of ignorance. Not a comforting feeling when dealing with this sort of gear.... unless it translates into cheap prices and an easy fix

author: bd139
author_rank: Super Contributor
timestamp: August 15, 2017, 07:58:14 am
content: Well it's pretty low risk. It's listed as used and passes self test. If it's broken and doesn't that's a pretty easy eBay refundI've got a few things stupid cheap from sellers who don't know what it is, list it as used and it doesn't work and only requires a simple fix. I got paid £100 back to change a fuse once. So that was a Tek 475 for £22.

author: Berni
author_rank: Super Contributor
timestamp: August 15, 2017, 08:47:54 am
content: Quote from: Jwalling on August 14, 2017, 09:23:35 pmI have looked it up and found the datasheet. It is indeed Brooktree, but its not a DAC.Its a 40bit to 5bit 250MHz shift register. So there are two of these per module to give you 8bit dac data + 2 markers at 250 MS/s and there are 4 of these modules to get you to 1GS/s. So its just used to funnel lots of slower RAM chips in to one fast narrow bus to feed the DAC.I don't see anything that is obviously a DAC, but there are lots of ceramic chips with heatsinks on them that we will never know what they are as the service manual is only board level. One possible candidate is the large heatsinked chip next to the two coax cables that carry the output to the analog front end PCB. But i think that chip is actually just a super fast 4:1 analog mux that combines together the output of 4 seperate DACs. Perhaps the DACs are under the memory modules.

author: analogRF
author_rank: Super Contributor
timestamp: May 29, 2018, 04:47:58 am
content: Quote from: Berni on August 14, 2017, 04:58:07 pmwhat error coder were you getting on the clock board? was it ?thanks

author: helius
author_rank: Super Contributor
timestamp: May 29, 2018, 05:42:25 am
content: Quote from: Berni on August 14, 2017, 04:58:07 pmThose arePeltola connectorsdesigned for in-house use by Tektronix.

author: Berni
author_rank: Super Contributor
timestamp: May 29, 2018, 05:53:15 am
content: Ah yes those are indeed the connectors.To me mostly looks like an attempt of making a RF connector cheaper. Not really a fan of having raw copper lightly pressing against a gold finger for contact. I suppose it would be a bit better if the coax was a bit nicer and had silver plating on the center conductor to hold back oxidation.

author: ebastler
author_rank: Super Contributor
timestamp: May 29, 2018, 06:54:22 am
content: Quote from: Jwalling on August 14, 2017, 02:14:15 pmHey, the condition description in the auction actually says: "Passedself test". It doesn't state when that last happened...

author: analogRF
author_rank: Super Contributor
timestamp: May 29, 2018, 11:11:07 am
content: what error coder were you getting on the clock board? was it ?thankssorry, I meant what error "code" was it!

author: Berni
author_rank: Super Contributor
timestamp: May 29, 2018, 12:00:11 pm
content: Quote from: analogRF on May 29, 2018, 11:11:07 amwhat error coder were you getting on the clock board? was it ?thankssorry, I meant what error "code" was it!I don't remember the number anymore, i just remember i was being told about a error with the clock board.Error codes are not always pointing exactly at the problem tho. Sometimes it can be another board misbehaving that is causing whatever its feeding to not work and throw an error. Tho usually this is power supply related, test gear often has pretty well made self tests in it.