This strange thing happened today to me, usually it doesn't go like this most of the time, I just heard stories, but finally it happened to me as well and now I really need your friendly and professional TEA advice, I'm in a bit of a pinch here. Please read to the and and advise from your gentle kindness .
lnitial post with a picture of the TE discussed here:
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3705673/#msg3705673Warning: long, almost JBG length
. !!!
To a couple of days ago I've posted that I've got a Tek TDS520A for a good price, advertised as defective from an
-bay seller that had some worrisome feedback regarding franken devices made of a collection of defective boards and of BD players missing the whole optical assembly
, but I needed one ceramic front section for my TDS724A that was inexplicably cracked
when I've got it,almost 9 yrs !!! ago. Nobody was able to help me with one, all recommending to "buy a defective one and use it as spare", well, 'gee thanks for advice, the only problem is that in DE/EU the most vile garbage was costing way to much, the US did have some nice pieces but shipping is ruinous and there was just one Chinese seller that advertised one of these sections as "working pull" (then why did you pull it ?!?), for nine years was costing more than what I've paid for the scope and for nine years the price just slightly increased (I think it is tracking the inflation). It also didn't sell in all these years, but the guy is tenacious
.
So I've thought, what the hell, it has four of these sections, maybe, just maybe, one had survived and I was wondering what is the black thing over the calibration signal pins (mystery solved, see below).
So the parcel arrives today morning, my last day of Urlaub (vacation), relatively nicely packed, not just paper but also Styrofoam placed in strategic place, ultra fast and nothing to comment, also DHL used something else for today karate training so was pretty non-banged, so far so good, nothing to comment here.
The device itself is extraordinarily clean on the outside, almost like new it has calibration stickers from 2020
and electrical compliance checking from 2021
!!!, but connected to the mains behaved as seller says, no power at all, just a faint "tit" when the switch was turned ON but that was it, no other reaction
.
So I open it expecting to find the collection of dead leaked elcos and eventually scavenged boards from 5 other devices, not necessarily related
, but the screws actually did this "unopened device" click, a thing that after so many years and devices opened is unmistakable, wtf, the mystery deepens
.
Inside absolutely immaculate boards, no leaked caps at all (used x2, x10, and x20 visors to inspect), nothing, just a bit of dust that was kicked out with some canned air and a soft brush, same looking a power supply, display assembly and and fan, OK, not it becomes REALLY strange. So, after snapping some pictures (see attached), I decided to put everything back together and use the troubleshooting procedure in the service manual, usually mostly useless, but what the hell, I was already having an eerie sensation.
So with the shield and mainboard put back, I start reading:
" - Q1: Do you have power on the cable ? A: Well, duh."
" - Q2: Is the cable inserted correctly ? A: GTFO.
" - Q3: Did you press the back mains power switch ? A: Come on maaan...
" - Q4: Did you press the ON/STBY button ? A: Uhmmm, actually not, but OK, for the sake of completion, let's press it, happy now mofo !!! wait what.... ?!?!
VOOOOM, booting !!!!, really, are you kidding me ?!?! Hold on a second, why is the screen black after displaying some strange patterns, could it be that the mainboard is done for ?, the little 7-segment digit counted very fast and then stopped with the upper segment lit and all the front panel leds are on, oh well maybe the attenuators are OK, should I commence the rape and pillage already, but hold on a second, what is this black rocker switch on the main board, let's flip it, some on put it in the calibration position and start it again...
VOOOM, monitor on, white blink..., ...strange patterns..., some seconds passes..., clickety, clickety, clack, (OK, that is new...) , and BANG: start up test passed, option 1M and other banner things...
It works, what the hell, this only happen to other people, not me ?!?!, damn, that means that the attenuators are actually toasted, this is why was sold for scrap, shit, shit, shit
!!!
So let's try some probes, even some Tek originals... HOLLY FECES, the signal DOES looked screwed up and totally not 0.5 Vp-p, OK then, lets not panic, wipe the sweat, let it run for a while to get it warm and run SPC, this will most likely fail and tell me if there are some attenuators left or they're all crispy.
SPC running, runninig, ruuuuuning...., done, SPC Passed, All tests passed, signal level and shape still screwed up, let's do a probe compensation what is to lose...
CH1: "Probe compensation succeeded, should overwrite the exiting data ? ", hell yes, do it. And same for CH2 and the other AUX1/2 channels, hallelujah God and saint patron of the TEA, whoever you are !!! IT ACTUALLY WORKS PERFECTLY with all the tests that I could (quickly) think off, this is completely strange, but hey, we live in interesting times, so what is actually this cute black thingie that I've removed from the calibration studs ?!?!
It's a
Tektronix Current Probe Calibrator 015-0672-50 where you hook your little current pincer, press a button and inject some current in the bar, achsooo, so this explains the strange level and signal shape for the exiting probe constants, they were CURRENT PROBES
!!!
So now the moment you were all waiting for, due to the small apartment where I'm living one of the TDS scopes HAS to go, there is literally no place for it, so I'm dong this poll of what should I do, please answer in your comment with the number of the option:
- 1) Change the attenuator board to the TDS724A and flip the TDS520A with reduced price (eventually sponsor a student/forum member for a token plus shipping, PM me in this situation, I have the packaging saved, tomorrow it cold leave to you).
- 2) Flip the TDS520A as a perfectly working device for some extra shekels and wait another nine years until a ceramic section will be available.
- 3) Flip them both in the most profitable configuration, you have enough scopes.
So before attaching some pictures to help you decide, thank you for your support and reading this loooong post.
Cheers,
DC1MC