Test Equipment Anonymous (TEA) group therapy thread

[bd139]

I have heard the same. Problem is it was slow if I remember correctly.

Completely stumped on this bastard. Just will not reliably trigger. Easier to diagnose a dead thing or a live thing but not an intermittent thing

[med6753]

I have heard the same. Problem is it was slow if I remember correctly.

Completely stumped on this bastard. Just will not reliably trigger. Easier to diagnose a dead thing or a live thing but not an intermittent thing

Why not set up a working scope next to the defective one with same settings and waveform and then do a comparison?

[tggzzz]

tggzzz: The original was on solderless board as well. And it had a note saying "only to annoy tggzzz" 

Nah. Have to try harder than that.

I only get irritated when someone asks me to debug (an approximation to) their circuit built on solderless breadboard - because I know I'll be wasting both our remaining lifetimes.

Hence I try, in vain[1], to help other people wasting their time.

[1] There's a Schiller/Goethe quote lurking nearby.

[bd139]

Why not set up a working scope next to the defective one with same settings and waveform and then do a comparison?

Waveforms are as per the service manual. Just they don't occur at the same rate as the ones in the service manual

Nah. Have to try harder than that.

I only get irritated when someone asks me to debug (an approximation to) their circuit built on solderless breadboard - because I know I'll be wasting both our remaining lifetimes.

Yes been there. To be 100% honest I tend to only use a breadboard to test an idea out. A very small idea. Or tweak some bias networks or opamp gain. This is then transferred to dead bug if it isn't there already. Usually looks like this (single supply quadrature oscillator prototype)

[med6753]

Why not set up a working scope next to the defective one with same settings and waveform and then do a comparison?

Waveforms are as per the service manual. Just they don't occur at the same rate as the ones in the service manual

If the correct pulse is there but at the wrong time wouldn't that indicate that the Trigger circuit is free running which would point to an issue in the Trigger Level control area?

[bitseeker]

Poor man's curve tracer. 33120A as curve source, scope ch1 as voltage (measuring voltage across D), ch2 as current (measuring voltage across R). Don't do this with a ground referenced function generator - won't work! Has to be floating, one reason I bought the thing!



Now for a tunnel diode output. This is why these things are rather cool. Notice the "blank" spot which is a zone of negative resistance.



And a 1N4148 just for fun.

That's pretty neat. Looks like a perfect combo for quick component testing.

[mnementh]

Utilized both the EEVblog promo code and my .edu email at Tequipment and ordered me a Hakko 301 desoldering gun, with extra tips and stand. In order to support repair of TEA of course. 

I'll try to refrain from mentioning the whole T12 OLED Controller exchange a few months ago... 

More solderless board fun to annoy tggzzz. Testing tunnel diodes out of that 475A. All test good. [PIC] Poor man's curve tracer. 33120A as curve source, scope ch1 as voltage (measuring voltage across D), ch2 as current (measuring voltage across R). Don't do this with a ground referenced function generator - won't work! Has to be floating, one reason I bought the thing!

Now for a tunnel diode output. This is why these things are rather cool. Notice the "blank" spot which is a zone of negative resistance.

I've heard that someone came up with an equivalent circuit that mimics the action of those unobtanium tunnel diodes but never saw said circuit. I think you'd probably have better luck getting stabbed in arse by a unicorn.

OWWWWW!!!! 

mnem
Dammitt... now I fart rainbow glitter!!! 

[0culus]

Utilized both the EEVblog promo code and my .edu email at Tequipment and ordered me a Hakko 301 desoldering gun, with extra tips and stand. In order to support repair of TEA of course. 

I'll try to refrain from mentioning the whole T12 OLED Controller exchange a few months ago... 

*snip*

Well, now you've piqued my curiousity. 

[bitseeker]

I'll try to refrain from mentioning the whole T12 OLED Controller exchange a few months ago... 

Well, now you've piqued my curiousity. 

I believe there's a link to it in the Points of Interest section of Post #1. Yes, it's under Electronics Miscellany.


In other news...

Oh, my! There will soon be 20 000 replies in this thread.

[Specmaster]

All the electronic books I've read recommend solder less breadboarding for prototyping. Could it be that today's high speed circuitry is not compatible with that format anymore due to stray capacitance causing all kinds of problems?

[Specmaster]

I'll try to refrain from mentioning the whole T12 OLED Controller exchange a few months ago... 

Well, now you've piqued my curiousity. 

I believe there's a link to it in the Points of Interest section of Post #1. Yes, it's under Electronics Miscellany.


In other news...

Oh, my! There will soon be 20 000 replies in this thread.

Yep, you certainly created a monster when you kicked this thread off [emoji1787]

[bitseeker]

All the electronic books I've read recommend solder less breadboarding for prototyping. Could it be that today's high speed circuitry is not compatible with that format anymore due to stray capacitance causing all kinds of problems?

In general, yes. However, even "old" ham radio circuits can be adversely affected by stray capacitance, inductance, etc. No?

[bd139]

All the electronic books I've read recommend solder less breadboarding for prototyping. Could it be that today's high speed circuitry is not compatible with that format anymore due to stray capacitance causing all kinds of problems?

They’re unreliable, full of stray capacitances and inductances, have no decent ground, are virtually impossible to place some components on and wear out pretty quick.

The reason people pick them is because they’re cheap and fast and work most of the time. Cheap because you don’t have to throw the components in the bin when you’re done and can reuse them. Fast because 3d dead bug puzzles get slower the more complicated they get. They’re just convenient. This makes them popular for home and college use at least.

If you think of them as a plastic phase shifter you get the idea generally.

All the electronic books I've read recommend solder less breadboarding for prototyping. Could it be that today's high speed circuitry is not compatible with that format anymore due to stray capacitance causing all kinds of problems?

In general, yes. However, even "old" ham radio circuits can be adversely affected by stray capacitance, inductance, etc. No?

A lot of the old ham radio circuits worked for the person making the circuit who wrote the book and no one else. Lots of crap out there!

[neo]

With med being kind enough to furnish me with schematics for a better power supply i dug out a 8000A. I actually have two, the first is junk and the second one has quite the odd problem. The digits light up as intended however only one at a time, it cycles between them. Anyone have any ideas for this one?

Just to note, someone has been in it before me and if this turns into a project rather than an inquiry i will start a thread for it... just throwing that second point out there to be safe 

[Specmaster]

That's true however IIRC they started becoming popular back in the era of electronics magazines  and people where experimenting with audio circuits and things with NE555 timer IC's and early calculators etc and little has changed with them since then but the speed of modern circuits has grown exponentially, especially in the comms world. 

[bd139]

Not necessarily. Even a 1Hz square wave is fast when you consider it using fourier. I like this graphic as a demonstration which shows a square wave represented as many sines visually:



Look how mad the little one is going. That can go out quite happily to 10-100MHz on a breadboard. If you connect your breadboard 1Hz 555 to a spectrum analyser it will find edges out to about 30MHz. The 2-3pF capacitance between the tracks there turns into an unexpected 1.7k resistor approx. This can couple out of phase signals back into an unexpected part of your circuit. Next thing you know your oscillator is an FM transmitter (been there done that) 

[tggzzz]

All the electronic books I've read recommend solder less breadboarding for prototyping. Could it be that today's high speed circuitry is not compatible with that format anymore due to stray capacitance causing all kinds of problems?

For logic, inductance is more the problem. During a transition, i=C^dV/_dt and the induced voltage is V_i=L^di/_dt. Now plug in values including 5V, 1ns, 5pF and 1nH per mm or wire, and compare V_i to the voltage margin. Then add several outputs switching simultaneously in the same package, which multiplies i and V_i pro-rata.

For analogue, transistor f_t (even for nominally identical devices, infamously the 2n3055), and op-amp GBW have increased enormously.

For anything remotely "RF", search for "gimmick capacitor".

And, of course, there is a lot of bad advice out there, especially from people that haven't considered the school-level physics involved.

[tggzzz]

Not necessarily. Even a 1Hz square wave is fast when you consider it using fourier. I like this graphic as a demonstration which shows a square wave represented as many sines visually:



Look how mad the little one is going. That can go out quite happily to 10-100MHz on a breadboard. If you connect your breadboard 1Hz 555 to a spectrum analyser it will find edges out to about 30MHz. The 2-3pF capacitance between the tracks there turns into an unexpected 1.7k resistor approx. This can couple out of phase signals back into an unexpected part of your circuit. Next thing you know your oscillator is an FM transmitter (been there done that) 

Have a look at some measurements of a signal: https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

That shows how the fundamental frequency and duty cycle are irrelevant: the only thing that matters is the rise/fall time.

[med6753]

I recall way back in the 1970's working in an engineering lab testing prototype logic boards. In that lab were our work areas plus multiple IBM 1130 computers and rows of tape drives and chain printers. Well this engineer handed me this board of MECL 10K logic that was supposed to be some sort of giant shift register. I connected it to the power and turned it on and noticed immediately that the current was oscillating back and forth between 5 and 10 amps. That ain't right. I started scoping some points and discovered the entire board was oscillating. No matter what point I scoped it was off to the races. What I had on the bench was one hell of a rf transmitter. And it promptly crashed several of the 1130 computers. Needless to say the room went ape shit and hilarity ensued. I shut off the power and called the engineer. He came out and looked at his logic diagram and suddenly realized that he had incorrectly looped an inverting and non-inverting outputs back on themselves creating an oscillator. D'OH.  He was some red faced for quite a while.       

[bd139]

Have a look at some measurements of a signal: https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

That shows how the fundamental frequency and duty cycle are irrelevant: the only thing that matters is the rise/fall time.

Very true which is one reason I like Philips: they put the rise time on their scopes.

And, of course, there is a lot of bad advice out there, especially from people that haven't considered the school-level physics involved.

Most of the bad stuff is attributable to ARRL and people with callsigns.

I recall way back in the 1970's working in an engineering lab testing prototype logic boards. In that lab were our work areas plus multiple IBM 1130 computers and rows of tape drives and chain printers. Well this engineer handed me this board of MECL 10K logic that was supposed to be some sort of giant shift register. I connected it to the power and turned it on and noticed immediately that the current was oscillating back and forth between 5 and 10 amps. That ain't right. I started scoping some points and discovered the entire board was oscillating. No matter what point I scoped it was off to the races. What I had on the bench was one hell of a rf transmitter. And it promptly crashed several of the 1130 computers. Needless to say the room went ape shit and hilarity ensued. I shut off the power and called the engineer. He came out and looked at his logic diagram and suddenly realized that he had incorrectly looped an inverting and non-inverting outputs back on themselves creating an oscillator. D'OH.  He was some red faced for quite a while.       

First "job" if you call it that I had was weekend lab hand at my univesity. Basically sweep and clean. I watched someone trying to work why exactly that was happening  ... very easy mistake to make. I didn't tell him as he was a PhD student and I was undergrad and after a bout or two of politics I didn't feel like helping anyone by then.

Just replaced screen on my sister's macbook pro after it got smashed. Nice and easy job that one fortunately.

[mnementh]

moo.

[mnementh]

moo?

[mnementh]

MOOO!!!

[mnementh]

Awww, come on someone... push us over the top!!!

mnem
I made that dot right there _~~~> .

[mnementh]

Not necessarily. Even a 1Hz square wave is fast when you consider it using fourier. I like this graphic as a demonstration which shows a square wave represented as many sines visually:



Look how mad the little one is going. That can go out quite happily to 10-100MHz on a breadboard. If you connect your breadboard 1Hz 555 to a spectrum analyser it will find edges out to about 30MHz. The 2-3pF capacitance between the tracks there turns into an unexpected 1.7k resistor approx. This can couple out of phase signals back into an unexpected part of your circuit. Next thing you know your oscillator is an FM transmitter (been there done that) 

I always looked at solderless breadboards as a antenna array you plug components into until an oscillator happens, then spend hours trying to uncouple said oscillator.   

About the only thing they're really good for is connecting crap to 0.100" spaced relays; anything faster than relay-relay logic and you're just begging for a loop. And yet, knowing this, I STILL have a dozen of the satanic little bastards in the back of my toolbox. 

mnem
DCCC!