Test Equipment Anonymous (TEA) group therapy thread

[med6753]

I never thought I'd ever say this but I wish my 547 issues were tants. 

[bd139]

This is why I don’t bother with those old scopes and am quite content to watch you arguing with them 

Btw for the sake of AVGresponding I got outbid on both the 7603 and 7623 . A small part of me is disappointed but a large part of me is actually happy about this 

[0culus]

I never thought I'd ever say this but I wish my 547 issues were tants. 

But once you diagnose and fix the problem, the scope should give you another half a century of service! 

[med6753]

The problem with this PSU design is while the -150V reference is the key there are so many feedback loops that it's confusing as to who starts who. The -150V does require the +100V to a least come up but at the same time the +225V has to come up plus the -150V to start the +100V. And reading the theory of operation for this PSU is like reading Greek. 

[xrunner]

The problem with this PSU design is while the -150V reference is the key there are so many feedback loops that it's confusing as to who starts who. The -150V does require the +100V to a least come up but at the same time the +225V has to come up plus the -150V to start the +100V. And reading the theory of operation for this PSU is like reading Greek. 

It was designed by the Ancient Ones - the ones who came before us, who possessed these Elder Scrolls. Consider it a privilege to learn from them grasshopper. 

[bd139]

If by the Ancient Ones you are referring to the Dark Lord Cthulhu then I'm with you. Some of their early designs were leveraging some rather bleeding edge and flakey ideas.

[Saskia]

Don't mention the name lest Azathoth pay you a visit ...

[Vince]

The problem with this PSU design is while the -150V reference is the key there are so many feedback loops that it's confusing as to who starts who. The -150V does require the +100V to a least come up but at the same time the +225V has to come up plus the -150V to start the +100V. And reading the theory of operation for this PSU is like reading Greek. 

If really, reallllllly you struggle beyond words to debug this entangled mess of a PSU... then as a last resort maybe you could try to isolate the -150V supply : I see it's connected to the +100V supply via 4 resistors. So you could try pulling the appropriate side of each of these resistors, and connect them to an external, floating power supply.. if you have one that can put out 100V ? If you don't, maybe put several in series. If not, since you have other old Tek scopes, just tap the +100V supply from one of them... and use an isolation transformer if you have one, to get that other Tek to float. That's if you have an isolation transformer that is ??

This way you can easily troubleshoot this now completely independent rail, and once you get it working, you can connect it back to the rest of the rails/scope, knowing it's good.

Anyway, I am following your mystery PSU issue very closely.. seeing as I have not one but two 547 to restore...

[Saskia]

@med good luck. I am confident that you will do it.

[BU508A]

The problem with this PSU design is while the -150V reference is the key there are so many feedback loops that it's confusing as to who starts who. The -150V does require the +100V to a least come up but at the same time the +225V has to come up plus the -150V to start the +100V. And reading the theory of operation for this PSU is like reading Greek. 

And that is exactly why you can't have too many PSUs and DMMs for watching voltages and currents.
I would disconnect every module of the scope (HV, vertikal amplifier, horizontal part etc.) and connect it back,
one after another, beginning with the ones which do consume the least amount of power.

But since you are a brave smurf, you'll track it down at least, I'm sure.   

[mnementh]

17 minutes in. Some capacitors giving out in a way that even RODALCO couldn’t even match

https://youtu.be/hVFARbqkUEc

Tony: your video got me onto this one after looking for loud server fans 

*POP!!! SMOKE!!! FSSSSSHHH!!!!*

"Holy fuck... this is good video...!"

     

BWAHAHAHAHAHA...!!!

mnem
 

[mnementh]

This weekend's 3DP Project:   18650 Li-Ion Battery for the headlight on my fatBike.



The battery pack is all made of what I call "electronic LEGOs parts"; commodity Coax DC power cords, a TP4056 charger/protection board and a toggle switch for main power. Total CAD$8-ish plus another couple dollars worth of filament, including extra iterations.



I really liked this little CNC headlamp the moment I saw it on Amazon; it was crazy cheap (like CAD$12), but it's got a genuine Cree XML so good for legit 180-ish lumens from a single 18650 cell. It has a CC driver in it that'll power safely from 3-9ish volts.

   

Entire battery slips inside the hollow handlebar stem riser. Main power switch and u-USB charge port are recessed so nothing protruding.  When I had to go with the handlebar riser tube because my extended handlebar neck simply wasn't high enough, it  seemed obvious that this was just how the thing had to be...

Lots more details & pics on my project post in the 3DP thread:   

https://www.eevblog.com/forum/3d-printing/3d-printer-yet/msg3566073/#msg3566073

mnem
 

[Cerebus]

This is why I don’t bother with those old scopes and am quite content to watch you arguing with them 

One of those things that is definitely better as an armchair sport.

[Specmaster]

17 minutes in. Some capacitors giving out in a way that even RODALCO couldn’t even match

https://youtu.be/hVFARbqkUEc

Tony: your video got me onto this one after looking for loud server fans 

Yuk, could almost taste and smell that stench 

[tautech]

Do I need another Tek P6021 AC current probe after just buying 3 new AC/DC current probes ? 

Tempting at this price with 5 hrs to go:
https://www.ebay.com/itm/203431829264?epid=1500403642&hash=item2f5d7b5f10:g:6WkAAOSwGSpgjr0w

Well I threw in a bid before going to Ded  and it still went for a very reasonable $255 considering it was listed as just opened.
Someone will be pleased at snapping this up for that money.

[mansaxel]

Did some signal chain tune-ups on the main stereo part of the multi-room system (you know the kind most people build with Sonos kit these days, but mine is analogue and crusty and alive! and funnier.) Also did complete the conversion to balanced feed for the line out to speakers, necessitating swap of RCA plugs to XLRs.  As I'd gotten to the point where I needed a reference, I turned to my Fostex TT15 oscillator, which was found to be dead, so dug out a series of "9V" batteries, mostly with 4,3V in them  but finally had to rob my 8022 of a working one. Then the 8060A could be put to service checking the gains of my buffer amp; I'm running a surplus balanced/unbalanced matching box between matrix and amplifier. All in all an outing in force, for I had MetraHit, 8060A, TT15 and the TS100 soldering kit doing service.  I'm mostly happy with the turnout. I got it to sound more even, and less noisy. There's a lot to be said for gain structure.

Last night I did start the recap of my Marconi VTVM. Not entirely certain what let the magic smoke out of it, for all caps tested OK. There is a selenium stack in it, so there are lots of suspects... Probably need to power it up naked and wait for the fog..

Also. I should get a tone generator for the audio matrix. I've got lots of free inputs ATM so a mains powered 0dBm 1KHz sine is on the desired list.

[bd139]

TEA archive script running again. I've added ability to start from a page offset this time so if it craps itself I can restart it. Reading page 2106 now...

I was going to implement retry logic but as it goes down for 3 days at a time I think that is probably a wasted effort 

[factory]

17 minutes in. Some capacitors giving out in a way that even RODALCO couldn’t even match

https://youtu.be/hVFARbqkUEc

Tony: your video got me onto this one after looking for loud server fans 

*POP!!! SMOKE!!! FSSSSSHHH!!!!*

"Holy fuck... this is good video...!"

     

BWAHAHAHAHAHA...!!!

mnem
 

Needs more flames. 



David

[bd139]

TEA archive script running again. I've added ability to start from a page offset this time so if it craps itself I can restart it. Reading page 2106 now...

I was going to implement retry logic but as it goes down for 3 days at a time I think that is probably a wasted effort 

Urf it turns out I balls'ed up the last TEA archive posting entirely. If you downloaded it, delete it. It's useless  .

Rerunning from scratch now. Poor gnif/Dave. As a side effect the database size is going to increase rapidly 

[factory]

The problem with this PSU design is while the -150V reference is the key there are so many feedback loops that it's confusing as to who starts who. The -150V does require the +100V to a least come up but at the same time the +225V has to come up plus the -150V to start the +100V. And reading the theory of operation for this PSU is like reading Greek. 

If really, reallllllly you struggle beyond words to debug this entangled mess of a PSU... then as a last resort maybe you could try to isolate the -150V supply : I see it's connected to the +100V supply via 4 resistors. So you could try pulling the appropriate side of each of these resistors, and connect them to an external, floating power supply.. if you have one that can put out 100V ? If you don't, maybe put several in series. If not, since you have other old Tek scopes, just tap the +100V supply from one of them... and use an isolation transformer if you have one, to get that other Tek to float. That's if you have an isolation transformer that is ??

This way you can easily troubleshoot this now completely independent rail, and once you get it working, you can connect it back to the rest of the rails/scope, knowing it's good.

Anyway, I am following your mystery PSU issue very closely.. seeing as I have not one but two 547 to restore...

I've tested the PSU board from an early design hp 180A separately, by using multiple supplies to eliminate problems caused by the failed section. Doing it by the book requires a shit-ton of spare fuses as procedure is to check parts & replace the blown fuse, power up & blow the fuse again and repeat till you've run out of fuses. 
Trouble is I still haven't got round to reinstalling the board in the scope now it's fixed. 
Later hp 18x series used a redesigned PSU that eliminated these problems.

David

[mnementh]

The problem with this PSU design is while the -150V reference is the key there are so many feedback loops that it's confusing as to who starts who. The -150V does require the +100V to a least come up but at the same time the +225V has to come up plus the -150V to start the +100V. And reading the theory of operation for this PSU is like reading Greek. 

It was designed by the Ancient Ones - the ones who came before us, who possessed these Elder Scrolls. Consider it a privilege to learn from them grasshopper. 

At least you actually have documentation... and a "theory of operation" section. 

mnem
Good hunting.

[Neomys Sapiens]

Don't mention the name lest Azathoth pay you a visit ...

Shoggoth off my lawn!

[mnementh]

Happy Mothra's Day everybody!

mnem

Well not everybody. Over here it's in 3 weeks. Why can't they agree on a date worldwide...

That just means y'all get to enjoy it twice!

mnem


*groannnnn* "I can't believe I ate the whole thing..."

Longo's chocolate strawberries FTW.

Huge, so sweet and ripe, and fresh-dipped in store. The look on wifey's face was sheer heaven.

mnem
*family time*

[25 CPS]

My truck wouldn’t turn over in the shopping mall parking lot the other day which led me to make an interesting discovery about the dashboard voltmeter.  It’s like all the other gauges on the dash that only come up once the body and engine control modules do which means the voltmeter can only be used to begin troubleshooting where the problem might be occurring in the electrical system if the electrical system is functioning enough to get the modules up and running.  Luckily the long neglected Fluke 12 in my truck’s tool box still worked.  The batteries have been in it since 2008 so I need to change those out.



Anyways, I went looking for a Simpson or Triplett VOM to permanently put in the truck’s toolkit and found this Triplett 630 with case and leads so it’s all self contained which is great locally and picked it up:





The idea there is to leave the VOM permanently in the truck and not have to worry about batteries, either the truck or in a DMM, in order to troubleshoot car problems and to have on hand for field use.  This should fit the bill perfectly.

[Neomys Sapiens]

Strange things are out there: a S.E.Labs scope relabeled as HAMEG and with a strange French plate on the rear explaining? the connection between those? WTF?

https://www.ebay.de/itm/393292067175?hash=item5b9208b167:g:DTYAAOSwoW1cjYS1