Test Equipment Anonymous (TEA) group therapy thread

[Saskia]

you are welcome

[Cerebus]

Thats it, paint a really nice picture of the state of Germany, must give you the job of enticing more tourism I think 

In Germany's defence, I've felt at least as safe there as I feel in London - which I think is something when you're in a foreign country where you barely know the language or much of the local customs. I've never felt as comfortable in France - where if push comes to shove I can actually speak the language 1/2 properly - as I have in Germany

[mnementh]

BravoV.......the package from me to you is FINALLY out for delivery. 

Don't know if I'll be on Discord today. The lady is here and not sure what she has planned.

That's really a pity. In the last sessions on discord (audio) there were "only" the usual suspects, ch_scr, Saskia, Specmaster, AVGresponding, Neomys Sapiens and me, interrupted only by a few show-ups of some others. Where are you guys? Do you really want the Germans to take over?  ;-)   

Yes, very much.

mnem
At least the trains will run on time...

Nope, the Japanese are renowned for their railways running to the second even.

I'm showing my age I guess... 

It used to be a near-universal joke (dark humor; pulling the Devil's tail) that during the 3rd Reich the trains always ran on time. To the minute. This was in part due to draconian penalties for failure to do so on passenger lines carrying important couriers, but also because of the fact that other trains were carrying Jews to Auschwitz, etc and der Führer's timetable would not be missed.

mnem
I'll just crawl back into my cave now...

[mnementh]

         MOMMMMIIIIEEEE!!!!

mnem
 

RAV4? Blue? Loves Texas?

Med, is that you?   

I did that to my wife's car a few days after she got it.     

She was not amused.

mnem
But she didn't make me take it all off until after she drove it to work and all her coworkers had seen it.

[tautech]

Med, is that you?   

We were warned, Med is MIA for a bit as he's otherwise occupied. 

[Robert763]

Just won a rarity on ebay, a variable PSU

Looks pretty normal but look at the voltage scale. Fills a nice gap in my power supply range. Fortunatly the seller didn't mention valve, tube or nixie or it would have gone a lot higher.
I only looked at the listing for one reason, but revealing that will have to await it's arrival.

[URI]

German trains and public transport ? Umm, no thanks, the train stations have turned into a no go area starting 2015.
Way too much risk to:
- get stabbed
- get tossed in front of an incoming train
- become a victim of a jihad bombing
- get stranded because the train breaks down
- get stranded because someone commits suicide or is murdered in front of the train
- get stranded because due to the long delay the train will not go to its destination but stop somewhere halfway.
- get stranded because some activist terrorist has sabotaged the tracks

As long as travelling by train is safer than travelling by car (it is!) I'm coming to the conclusion that your view is somewhat overly pessimistic.      

I'd say travelling by train in Germany is one of the last adventures left though.
Even if the train is in time when you get on it you'll never know whether you'll arrive in time or spend the night on the train...      

[tggzzz]

I'd say travelling by train in Germany is one of the last adventures left though.

I'm afraid your sense of adventure is sadly limited

[med6753]

         MOMMMMIIIIEEEE!!!!

mnem
 

RAV4? Blue? Loves Texas?

Med, is that you?   

I thought med had a Honda CR-V?

Correct.

[0culus]

So one thing the 519 is actually really useful for is TDR. It's got two onboard fast rise time step generators, so doing this measurements requires only one instrument. And the small downside you have really need to bring the work to the scope... 

[Microdoser]

This thread has more posts per day than the rest of the board!

 

[BU508A]

This thread has more posts per day than the rest of the board!

 

Because this is one of the most entertaining, informative and friendliest threads in the EEVblog forum.

(and we have to make sure, that bitseeker has to do some really serious catchup)   

[0culus]

So one thing the 519 is actually really useful for is TDR. It's got two onboard fast rise time step generators, so doing this measurements requires only one instrument. And the small downside you have really need to bring the work to the scope... 

Made a little more progress with the last remaining issue with this scope. The calibration step generator doesn't work. Narrowed it down essentially to the reed relay. I removed the output line (it's a long tube which goes all the way to the rear of the instrument, and connects to another 125 ohm GR-874 back there) and found that the reed relay was basically loose inside. I put it back, and now it buzzes. Still no output that I can discern, even on an external oscilloscope into a 50 ohm load (through a 125/50 through termination). So the reed is probably worn out unfortunately. I need a 125 ohm coax so I can connect the output directly to the 519 input. 

[mnementh]

Y'all may have noticed that the ol' TinkerDwagon hasn't been in here rousing the rabble all day...      That's because he done wents on a road trip.   

I met with fellow TEA member  cyclin_al to trade off some of those Dell server PSUs I've been buggin' y'all with for some TE, of which I'll post pics of tomorrow, I think...

As threatened... some actual TEA today!!!   


This all started aboot a month ago, when I spotted this beauty on Kijiji for a mere CAD$50, advertised as "working, but output distorted when set above approx 1V", but pick-up only in Kanata, just South of Ottowa. I figure maybe a toasted diff amp or short pass transistor on the output, (really hoping NOT a fault in the DAC) so I PMed cyclin_al, and after some discussion we struck a deal for him to pick it up for me. A really long and ahem... amusing bit of "real life" later, this turned into a deal to trade 3 of my Dell PSUs for the 4070A.  al watched my adventures in 3DP with some amusement; when the PSUs were ready we decided to meet up in Madoc to do our trade, and this was my half of the deal.




Initial testing... 500mV looks pretty good on all standard generator functions.




Uh-oh... now not so good-looking. Similar distortion on all other functions as well.




And really bad, as promised at 1000mV. Similar distortion on all other functions as well. Twiddling the knobs on my scope, I notice the waveform disappears offscreen downwards... suggesting a negative DC offset.




In hindsight, I really do wish I'd thought it through, considering how close I might have come to frying the frontend on my  with this connected directly... in my defense, I DID check for voltage difference between the BNC GNDs BEFORE I connected the two; I ALWAYS do this before testing or probing anything. But I did it; it's done and this was the result after I popped off the 50Ω terminator to probe with my meter. Yup... as suspected... -12VDC. FuckFuckFuckFuckFuckFuckFuck! -12V DC on the output, and no terminator acting as a shunt to protect my 54645A!!! 

A quick check, and yes... I'm still in standard waveform mode, and there is no DC offset dialed in. It really is just dumping -12VDC across the output.  Time to take it apart.




So... cracked rubber bumper ring fixed with tape... some grrilla haz been in this thing. 




You have got to be fucking kidding me... 



Oh, this just keeps getting better. But hey... at least the grrilla knows what heat-shrink tubing is.




Wow... really? WTF is with this ground wire...?

Time to do some testing. Okay... MCP on the output tests okay with junction test... no obviously shorted relays... no shorted tants in the output quadrant of the mainboard. Remove the PSU.... and actually, not that bad. That weird soldered GND wire is actually soldered to a eyelet to go under a screw on the PSU.




So I hop on the intardnet to look for some tech ref... and I stumble across this teardown video. It looks like the damaged rubber bumper is endemic to the design... it happened to his just like mine. Also, upon reviewing the video, I can see the GND wires soldered onto the AC Line Filter appears to be the way they were made... as are many of the DIP packages hand-soldered... and that DAC being sanded off too.

I'm thinking maybe... all that horrible stuff (aside from the obvious fan hack) may have been the way it was made, and this unit was just produced during the death throes of B&K as a manufacturing entity in the US... before they became entirely a paper company having everything made by other people. And maybe "Give a fuck" was in short supply.

*sigh*

Okies... I have every shred of support off the B&K site... even have the software for generating waveforms... but cannot seem to find a service manual or schematic. The vid above states this is a repackaged BNC Berkeley Nucleonics 625 or Telelux SG-100; I'm going to continue to seek out any available tech ref I can find on those, but I think now I'm going to need to actually start scoping this thing out live to see where the DCV is being injected and the distortion starts.

Pray for me guys!

   

EDIT: Okies... So far, the only resource I've found is this schematic for the Telelux SG-100. Not very good, but enough to grok how the amplifier chain and attens all work. I think. I've attached it here for posterity's sake. 

   

Here are some cleaned up versions of that schematic I made for my own use and posted in the originating thread. For future generations.


mnem
 

[0culus]

So one thing the 519 is actually really useful for is TDR. It's got two onboard fast rise time step generators, so doing this measurements requires only one instrument. And the small downside you have really need to bring the work to the scope... 

Made a little more progress with the last remaining issue with this scope. The calibration step generator doesn't work. Narrowed it down essentially to the reed relay. I removed the output line (it's a long tube which goes all the way to the rear of the instrument, and connects to another 125 ohm GR-874 back there) and found that the reed relay was basically loose inside. I put it back, and now it buzzes. Still no output that I can discern, even on an external oscilloscope into a 50 ohm load (through a 125/50 through termination). So the reed is probably worn out unfortunately. I need a 125 ohm coax so I can connect the output directly to the 519 input. 

Update: it appears the reed just needed to run for a bit...it's now producing output. 

[Specmaster]

Med, is that you?   

We were warned, Med is MIA for a bit as he's otherwise occupied. 

No he's not, he joined us tonight on discord.

[0culus]

So one thing the 519 is actually really useful for is TDR. It's got two onboard fast rise time step generators, so doing this measurements requires only one instrument. And the small downside you have really need to bring the work to the scope... 

Made a little more progress with the last remaining issue with this scope. The calibration step generator doesn't work. Narrowed it down essentially to the reed relay. I removed the output line (it's a long tube which goes all the way to the rear of the instrument, and connects to another 125 ohm GR-874 back there) and found that the reed relay was basically loose inside. I put it back, and now it buzzes. Still no output that I can discern, even on an external oscilloscope into a 50 ohm load (through a 125/50 through termination). So the reed is probably worn out unfortunately. I need a 125 ohm coax so I can connect the output directly to the 519 input. 

Update: it appears the reed just needed to run for a bit...it's now producing output. 

I found it works better with the variable amplitude since I don't have the 125 ohm coax available.

[Kosmic]

puuh. Mafia Market dood it again and separated me from a third of my monthly salary. They offered me a Canon RF 15-35 2.8L with an 800 Pesos discount. I could not resist.

I thought you had a EF 17-40 L series ? f/4 for me on the 17-40 is plenty since I mostly do landscape with that lens.

[Saskia]

Unfortunately the 17-40 fell to its demise. I was then looking at the other options and would have gotten the ef 16-35 f/4, however could not resist the offer.

[AVGresponding]

Bought a Thandar portable scope... can't claim this one as accidental, as I was in a back-and-forth offers exchange with the seller.


I couldn't resist posting this; it's a picture of...


A 508 BUs!   

I like it!      
Where can I get one?   

Anywhere between Halifax and Leeds, via Bradford!   

https://moovitapp.com/index/en-gb/public_transportation-line-508-Yorkshire-2109-1801031-27263984-0

[mnementh]

...I have every shred of support off the B&K site... even have the software for generating waveforms... but cannot seem to find a service manual or schematic. The vid above states this is a repackaged BNC Berkeley Nucleonics 625 or Telelux SG-100; I'm going to continue to seek out any available tech ref I can find on those, but I think now I'm going to need to actually start scoping this thing out live to see where the DCV is being injected and the distortion starts.

Pray for me guys!

My research eventually led me back to eevBlog and this thread: https://www.eevblog.com/forum/testgear/bnc-625a-firmware/   which has some discussion of how the unit works, and what the differences are between it and the base model Sig Gen without Arb, and upgrading the latter.

Hoo boy... there are a multitude of sins committed inside this little beige box. They're running it with +/- 15VDC rails, board is marked +/- 12VDC. And yes, that is the PSU B&K used (see that discussion), so it's calibrated to those rail voltages.  Heatsinks on MCP transistors at outputs and on AD811AN ICs are all hand made from aluminum sheet and U-channel... cemented in place with clear silicone sealant.    Power switch is constructed with a piece of square Plastruct rod heat-shrinked to the switch.   And it appears the chips that were hand-soldered were those necessary to make this mainboard into the ARB version.   

So far, the only actual resource I've found is this schematic for the Telelux SG-100, linked from that thread; somebody is still hosting it 8 years later.    Not very good quality, but enough to grok how the amplifier chain and attens all work. I think. I've attached it to my original post for posterity's sake. 

For the sake of my sanity and in hopes of actually fixing it rather than breaking it more, I'm going to pull the plug on this project for the night and attack it with a fresh brain after a good night's sleep.

mnem
*knocks self unconscious with a sinewave mallet*

[VK5RC]

Is Q2 C to E shorted?

[bd139]

It's going to be something like that. Not much different to the output stages on TTi stuff.

I'd load the output with 50 ohms and then work back up the signal chain from the output until you get a signal that isn't sick.

[mansaxel]

industry. ministry is fine

Yeah, my point too.

As soon as you get away from the screaming drill sgts (we don't have much of that here, though) and get to work, people usually are good and clever. There were more officers than privates where I worked; basically only the guards were soldiers, watching over a bunch of civilians and comms people.

[Kosmic]

Unfortunately the 17-40 fell to its demise. I was then looking at the other options and would have gotten the ef 16-35 f/4, however could not resist the offer.

Ok. Look like you had a good deal