Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

As a kid, I thought we were celebrating that Fawkes had tried to blow up the Houses of Parliament, not the fact that he failed.

The official line, that we celebrate his failure, and the popular view are at variance. I have been known to mutter on recent Nov 5ths "Guido, where are you when your country needs you?".

In the mid-80s in lat October[1] you could buy a full-size cardboard cutout of Margaret Thatcher. It turned heads when people saw it sitting in the passenger seat of my Land Rover.

As we learned as kids...
Remember remenber the 5th of November
Gunpowder treason and plot
I see no reason why gunpowder treason
Should ever be forgot.

[1] Bonfire night is November 5th.

Did you have a crush on the old girl and have the song "Maggie Mae" on continuous loop? 

I think "Maggie's Farm" would be a more fitting song.

McBryce.

Ahem. Politics. Y'all demanded zero-tolerance. I've complied.

At least try not to rub it in my face, please.

mnem
Just say "No, thank you."

Oh please. No one pissed in your wheaties this morning. Not politics, just good natured ribbing. You need more caffeine and try again. 

Yeah, NO.

I got trolled, and then spanked by Dave for posting something that wasn't even Politics, and since then I've steered far clear.

THIS is what zero-tolerance looks like. Either deal with it, or cut me some slack. Otherwise, you're being just as hypocritical as you thought C was being when he reversed position on my pet peeve, intolerance.

Cheers,

mnem
You asked for this.

[Cerebus]

I seem to recall someone on the radio forum mentioning a repair training instructor, that died after not discharging the HV capacitor, as Clive said never trust the built in discharge resistor.

David

Time for one of my regular Eevblog forum public service announcements:

When dealing with any component that may store significant charge (especially capacitors):

• Switch off
• Isolate
• Dump
• Earth

"S.I.D.E."

This rather excellent film "On the safe SIDE" produced at the UKAEA's Culham Laboratory during very early work on fusion energy research explains all:



It's also notable for being used as one of the "trade test films" transmitted on BBC2 outside of normal programming hours while colour TV transmission was being introduced to the UK.

Some of those trade test films were responsible for me being a very over educated Junior School pupil as I regularly watched them when I went home for my lunch. Certainly beats the stuff that kids who get dumped in front of the TV while mum gets on with something else get to watch nowadays. The modern generation get "Timmy Time", "Waffle the Wonder Dog", "Bitz and Bob", and "Go Jetters" (I quote tomorrows BBC children's lunchtime schedule) I got instruction on how nuclear and conventional power stations work, how to service colour TVs and high voltage safety. I think I got the better bargain.

[Cerebus]

No one pissed in your wheaties this morning.

Are you sure that isn't part of the Gwyneth Paltrow version of the keto diet that he's trying out? 

[BU508A]

Wanna see some expensive binding posts? Only 124 Euro.

Or some fancy Schukostecker for 370 Euro? Yes, for one piece.

You can get them here and many other ones:
https://www.ebay.de/sch/i.html?_dkr=1&iconV2Request=true&_ssn=diy-audio4you&store_name=diyaudio4you&_oac=1&_dmd=1&store_cat=1238912014

[Cerebus]

Or some fancy Schukostecker for 370 Euro? Yes, for one piece.

Is that like a "Schwanzstücker"? 

[McBryce]

For anyone along the 3DP front, some food for thought - how should this be to fit your scope / desk / workstyle?
https://www.printables.com/de/model/180580-oscilliscope-probe-organizer
I like the idea in general, only immediate flaw is it needs flat, free desk space in front of the scope to open the drawers 

The outer case definitely needs to be a different colour! I'd also colour the drawers the same as the channel colours and make them bigger so that the probes aren't coiled so tight.

McBryce.

[mnementh]

Wanna see some expensive binding posts? Only 124 Euro.

Or some fancy Schukostecker for 370 Euro? Yes, for one piece.

You can get them here and many other ones:
https://www.ebay.de/sch/i.html?_dkr=1&iconV2Request=true&_ssn=diy-audio4you&store_name=diyaudio4you&_oac=1&_dmd=1&store_cat=1238912014

139.80€ with shipping. For ONE pair of binding posts.   

For $20 less, I got 3 pairs delivered... and they happened to come with a couple Lambda LQ-532s as packing material. 

mnem
 

[mansaxel]

This rather excellent film "On the safe SIDE" produced at the UKAEA's Culham Laboratory during very early work on fusion energy research explains all:

"Discoveries in experimental physics are never made by rigid minds."   

Very random observation on Culham. Nearest  railway station is also called Culham, "CUM" in shorthand. Adjacent to the railway station, there is a B&B / pub, called the Railway Inn. Very robust experience.  OK food. Good, full English, breakfast. Beds tolerable. Would stay again.

[mnementh]

Bangers & mash...?

Actually, that reminds me. I read somewhere a long time ago... that it isn't proper bangers & mash unless the mashed taters have been fried in the sausage fat after they're mashed...? That seems uncharacteristically a lot of work for peasant food...? Any of you scone-eaters know  they were talking about?

I've made mashed taters fried in butter and it is a different flavor for sure... but it takes a lot of care to do without just making soupy mashed taters. 

mnem
Mmmm... all those yummy carbble-hydrapes...

[Specmaster]

Guessing they don't bother to read the warnings on unit, but the last rusted out one I scrapped, doesn't mentioned anything about death.  Still not found any of those modern high frequency switching transformer versions, guess copper coloured aluminium wire & steel is cheaper. 


I seem to recall someone on the radio forum mentioning a repair training instructor, that died after not discharging the HV capacitor, as Clive said never trust the built in discharge resistor.

David

Well, there are sensible people and then there are dumbasses and those are the ones who maybe did read the label and only saw reference made to the input voltage of 220-240V and thought that's nothing special, possibly even thinking that the actual voltage of the winding of interest was going to be considerable lower as indeed are 99.9% of all transformers are stepping the voltage down 

[m k]

Once happened so that noob was testing CRT power modules with a test rig.
He then changed to next module with power on and obviously disconnected the flyback with bare hands.
The table frame was grounded for Wrist Wraps.
The noob had also a keyring with multiple keys and banana jack was too close.
Luckily right hand and right keys were involved.

Can't remember how the loop was closed.

I gave up personal ornaments, and long hair, decades ago.

[m k]

An ADG368, an ADG368, my kingdom for an ADG368......


So, dealing with a recalcitrant TDS754D here that apparently lost its cal constants from the EEPROMS (U1052 and U1055) on the acquisition board.
I've had luck replacing them in the past, but this time I can't read or write anything to or from them using the EEPROM/NVRAM read/write utility stuff from somewhere on the forum that I put on floppy disk (It works on another working scope so my disks are good).

I replaced the EEPROMS with brand new ones and then tried writing the cal data from another TDS754D to at least get something force-fed in there but no dice...

So taking a look at the schematic, the EEPROM write control pins are tied to a 74HC86, which receives 5v from the famous 'Write Enable' switch on the processor board, via a 15V to 12V vreg and voltage divider.
All voltages test ok, so I replaced the 74HC86 because it was easy, still no dice. hmmmm.

I have also double checked all traces for continuity, all perfect like the day it was born.

So, the I2C data comes from a 160-pin chip, ADG368. Hmmm, all my spare boards use ADG308 chips. Well, lets get the hot air gun out and swap to see... No boot. Shiet, incompatible.
Swap back and we are booting again but errors are back to square one. So I think the ADG368 chip is most likely the bad bit at this stage (or whatever is feeding the AGD368..) I'll have to scope the I2C lines to the EEPROM chips too, to see if there is activity there.

Now, about finding another ADG368......... 

Last resort, pull good EEPROMS full of cal data from a scrapped TDS754D, stick them in and hope it works, if so, call it good. 
I also want to rig something up to directly read the data from the old EEPROMs to see if they might actually still be good, maybe something is just stopping the disk utility (and hence the scope) from seeing the data.
How can I do that with the bare chips in my hand? I have a bunch of programmers and chip clips etc but I'm not up with writing and reading directly to I2C chips...

Any idea what that 12V does?
My guess is that some version of NVRAM needed it for writing.

The 12V is brought down to about 5V with a voltage divider to provide 5V to the Write Protect pin on the EEPROMs to put them into write protect mode.
It also goes through some other bits and pieces of logic and ends up connected to the write protect pins on the NVRAM's.

Do you mean the 12V line from top of R2009?

How many NVRAMs there are?

[med6753]

Once happened so that noob was testing CRT power modules with a test rig.
He then changed to next module with power on and obviously disconnected the flyback with bare hands.
The table frame was grounded for Wrist Wraps.
The noob had also a keyring with multiple keys and banana jack was too close.
Luckily right hand and right keys were involved.

Can't remember how the loop was closed.

I gave up personal ornaments, and long hair, decades ago.

Always been policy in IBM systems test.....no jewelry, no rings, no watches. 

[Specmaster]

Once happened so that noob was testing CRT power modules with a test rig.
He then changed to next module with power on and obviously disconnected the flyback with bare hands.
The table frame was grounded for Wrist Wraps.
The noob had also a keyring with multiple keys and banana jack was too close.
Luckily right hand and right keys were involved.

Can't remember how the loop was closed.

I gave up personal ornaments, and long hair, decades ago.

Always been policy in IBM systems test.....no jewelry, no rings, no watches. 

Thats sensible.

[TERRA Operative]

An ADG368, an ADG368, my kingdom for an ADG368......


So, dealing with a recalcitrant TDS754D here that apparently lost its cal constants from the EEPROMS (U1052 and U1055) on the acquisition board.
I've had luck replacing them in the past, but this time I can't read or write anything to or from them using the EEPROM/NVRAM read/write utility stuff from somewhere on the forum that I put on floppy disk (It works on another working scope so my disks are good).

I replaced the EEPROMS with brand new ones and then tried writing the cal data from another TDS754D to at least get something force-fed in there but no dice...

So taking a look at the schematic, the EEPROM write control pins are tied to a 74HC86, which receives 5v from the famous 'Write Enable' switch on the processor board, via a 15V to 12V vreg and voltage divider.
All voltages test ok, so I replaced the 74HC86 because it was easy, still no dice. hmmmm.

I have also double checked all traces for continuity, all perfect like the day it was born.

So, the I2C data comes from a 160-pin chip, ADG368. Hmmm, all my spare boards use ADG308 chips. Well, lets get the hot air gun out and swap to see... No boot. Shiet, incompatible.
Swap back and we are booting again but errors are back to square one. So I think the ADG368 chip is most likely the bad bit at this stage (or whatever is feeding the AGD368..) I'll have to scope the I2C lines to the EEPROM chips too, to see if there is activity there.

Now, about finding another ADG368......... 

Last resort, pull good EEPROMS full of cal data from a scrapped TDS754D, stick them in and hope it works, if so, call it good. 
I also want to rig something up to directly read the data from the old EEPROMs to see if they might actually still be good, maybe something is just stopping the disk utility (and hence the scope) from seeing the data.
How can I do that with the bare chips in my hand? I have a bunch of programmers and chip clips etc but I'm not up with writing and reading directly to I2C chips...

Any idea what that 12V does?
My guess is that some version of NVRAM needed it for writing.

The 12V is brought down to about 5V with a voltage divider to provide 5V to the Write Protect pin on the EEPROMs to put them into write protect mode.
It also goes through some other bits and pieces of logic and ends up connected to the write protect pins on the NVRAM's.

Do you mean the 12V line from top of R2009?

How many NVRAMs there are?

Ah, my bad. That arrowhead on the 'NVWR_EN/I' is actually the line going to the NVRAM's, there are two of them, one containing the RTC.

[25 CPS]

Once happened so that noob was testing CRT power modules with a test rig.
He then changed to next module with power on and obviously disconnected the flyback with bare hands.
The table frame was grounded for Wrist Wraps.
The noob had also a keyring with multiple keys and banana jack was too close.
Luckily right hand and right keys were involved.

Can't remember how the loop was closed.

I gave up personal ornaments, and long hair, decades ago.

Always been policy in IBM systems test.....no jewelry, no rings, no watches.

That's always been my personal policy as well after seeing too many accidents when I was starting out and hearing too many horror stories.  There was one guy at work who used to laugh about that when I first started there until I pointed out that my employee passcard holder with the metal clip on it could short something out right below my face if it flopped around and landed on the wrong thing.  Why would you want a nasty walloping from the equipment when there are plenty of those coming from management already?

[Specmaster]

For a few moments this afternoon, I thought I was going to be getting some more TEA but no, it was not to be, I was pipped at the very last second, either that or someone already had a higher bid than mine, I maxed out at £30 because it was not 100% certain it was working correctly and sold as spares, it went for in the end £31, oh well, so be it.

[Cubdriver]

Good grief, there are some dumbasses around, just seen this video from Big Clive. I think these people must fall into the category that mnementh talks about.



One of the reasons, why I don't like Mehdi's videos very much. He is sending out the wrong message imo. ("You can get away messing with electricity.")

Yikes!!  Making a Jacob's Ladder from a microwave oven transformer is begging for trouble, fire and melted things - they have no current limiting.  Best bet is to use either an oil burner ignition transformer or a luminous tube (neon sign) transformer - both are designed to operate into low impedance loads and have magnetic shunts to limit their output current.

-Pat

[TERRA Operative]

Another TDS700 series scope lives again! 

So, this TDS714L I just fixed, it had no video on the internal CRT, but did boot fine and would output video on the rear VGA connector.
On closer inspection, I found that the CRT was cracked (This unit was obviously dropped, but not too much external damage beyond cracked feet etc), so that was replaced with one from a junker scope that had a good CRT.
Too bad, so sad, no video still.... Poking around I found that the main video processor isn't outputting a video signal, but the separate chip doing the rear panel VGA output is fine.
The video processor has an 80MHz crystal that is a known failure point, and mine turned out to be busted (I bet from the shock of that drop), so that was swapped with a replacement from a junk board. Still sadness and no video... 

I poked a few things more, swapped the main video processor (and now got memory errors due to an unexpected data value, could be an ID thing from different versions etc) but still no video, so it's looking more and more like a job for probing at the PCB with another scope and doing some signal tracing... Meh, I'm getting tired now, lets take a look at my spare processor boards.... 

Turns out that internally the TDS714L looks very much like a TDS7xxD, just with a different ID resistor combination to make it the TDS714L, it even uses the same firmware, but I don't have a spare 'D' version processor board. However, I do have a spare 'C' version board that looks identical to the TDS714L. Could be that this spare one I have is a later version 'C' board?.. I'm not sure, but it is running v6.x firmware, typical for 'C' boards.

I stuck it in anyway and it booted most of the way (showing the boot sequence video! a small win), but ultimately failed and hung on the final acquisition board checks... hmmm....

Well, how about I just try flashing it with the 7.xx firmware that's found on the 'D' series boards and in the TDS714L too, just for shits and giggles?
Time to connect the GPIB adapter, flash v7.4e firmware and also a copy of the original TDS714L NVRAM (for all the options and settings and stuff, just in case).

Bingo, bango, bongo! It JUST FREAKING WORKS!!!     


So that's interesting.... I know there are a number of revisions of the processor boards and this processor board will work with this acquisition board but not that one, and that processor board won't work with this acquisition board but will work with that one, etc etc, but I wonder if the real limiting factor is that the firmware version in the processor board needs to match the acquisition board version and the processor board will just 'go along for the ride'...?....

Hmmm, it seems it could be so with my tests so far, a 'C' version processor board works with a 'D/L' acquisition board only when firmware is updated to 'D' version firmware.
Also, I repaired a TDS620 with a TDS700 series processor board (with the relevant video chips swapped over to convert it from colour to monochrome) and also that all important firmware change to match the TDS620 and it boots fine (and feels more responsive, maybe a faster CPU? The presence of the extra video RAM?).


Anyway, that's another TDS scope fixed and on the 'to sell' pile, 6 scopes now ready to sell, and one last one to fix, once I figure out the golden ticket to get the machine reading and writing cal data to those damn EEPROM's.....

[med6753]

Finally got some time to start the re-cap of the Type 547. Started with C802, which is part of the decoupling network to keep the HV oscillator from feeding back into the PSU. Original was a 40uf/400V. Could have used either a 39uf or 47uf. Went with the 47uf/400V. The replacement cap was small enough that I could mount it inside the HV assembly and leave the original can in place.

Much more to do. If I work for a while everyday will probably take a week to complete. 

[cyclin_al]

Here's my Chinesian contribution, still better that that POS:

eBay auction: #https://www.ebay.co.uk/itm/284443493043

Link is borked, not that I want that one.

Is there any reason why these couldn't be made from a square of regular copper PCB, or even a square of copper plate?

David

This one is working: https://www.ebay.com/itm/284443493043

UK version: https://www.ebay.co.uk/itm/284443493043

Maybe because of thermal mass. A copper plate will take much longer to reach equilibrium than a PCB with some copper traces.

+1 to what BU508A just said. To avoid thermal EMF, you want a short with a low thermal mass to reach the temperature of the connectors on the multimeter quickly.

Also notice the low gauge wire used on the rustic Agilent short.

I was absolutely certain that someone would comment on the shorting block used in this video (fast forward to 8:10):

Marco Reps got a black 3458B 3458A last year from Keysight:

[BU508A]

Finally got some time to start the re-cap of the Type 547. Started with C802, which is part of the decoupling network to keep the HV oscillator from feeding back into the PSU. Original was a 40uf/400V. Could have used either a 39uf or 47uf. Went with the 47uf/400V. The replacement cap was small enough that I could mount it inside the HV assembly and leave the original can in place.

Hm. I'd have probably used a 39µF electrolytic capacitor and parallel to it a 820nF foil capacitor and a 100nF ceramic capacitor for better RF blocking.

[med6753]

Finally got some time to start the re-cap of the Type 547. Started with C802, which is part of the decoupling network to keep the HV oscillator from feeding back into the PSU. Original was a 40uf/400V. Could have used either a 39uf or 47uf. Went with the 47uf/400V. The replacement cap was small enough that I could mount it inside the HV assembly and leave the original can in place.

Hm. I'd have probably used a 39µF electrolytic capacitor and parallel to it a 820nF foil capacitor and a 100nF ceramic capacitor for better RF blocking.

Why? The original circuit didn't have that. Also, the HV Oscillator is completely enclosed in a metal case although I have not seen any degraded performance or noise with the cover off. But your point is well taken because if you run a Type 535A with the case open you DO see noise on the trace. I've seen it myself on my Type 535A but not on any of my three Type 547's. 

[BU508A]

Finally got some time to start the re-cap of the Type 547. Started with C802, which is part of the decoupling network to keep the HV oscillator from feeding back into the PSU. Original was a 40uf/400V. Could have used either a 39uf or 47uf. Went with the 47uf/400V. The replacement cap was small enough that I could mount it inside the HV assembly and leave the original can in place.

Hm. I'd have probably used a 39µF electrolytic capacitor and parallel to it a 820nF foil capacitor and a 100nF ceramic capacitor for better RF blocking.

Why? The original circuit didn't have that. Also, the HV Oscillator is complete enclosed in a metal case although I have not seen any degraded performance or noise with the cover off. But your point is well taken because if you run a Type 535A with the case open you DO see noise on the trace. I've seen it myself on my Type 535A but not on any of my three Type 547's.

Yeah, you are probably right. Sometimes I'm running in a "EMC paranoia mode"   
Nowadays the electrolytic caps are much better RF wise than the old ones from the sixties.

[Specmaster]

Finally got some time to start the re-cap of the Type 547. Started with C802, which is part of the decoupling network to keep the HV oscillator from feeding back into the PSU. Original was a 40uf/400V. Could have used either a 39uf or 47uf. Went with the 47uf/400V. The replacement cap was small enough that I could mount it inside the HV assembly and leave the original can in place.

Hm. I'd have probably used a 39µF electrolytic capacitor and parallel to it a 820nF foil capacitor and a 100nF ceramic capacitor for better RF blocking.

Why? The original circuit didn't have that. Also, the HV Oscillator is complete enclosed in a metal case although I have not seen any degraded performance or noise with the cover off. But your point is well taken because if you run a Type 535A with the case open you DO see noise on the trace. I've seen it myself on my Type 535A but not on any of my three Type 547's. 

I've always been told that it is better to increase the capacitance rather than drop its value, so with that in mind, I'd have done exactly the same as you and go with the 47uF