Test Equipment Anonymous (TEA) group therapy thread

[neo]

In that case you should be able to trace those wires from A to B and reconnect them to their correct locations. There's nothing to that scope is there, its very spartan

I wouldn't call 1600 volts and 400 some volts flying around the place nothing but then again i am a solid state guy, so far anyways.

The voltage is the main thing keeping me from just digging in, for fear of really screwing it up.

[neo]

After a few hours of digging and taking out the filter caps to redo them i discover the cause of at least some of my problems. The 1 megohm pot for spot shape went completely round the bend at some point.
 Whether it was pre-existing or the result of a screw up i don't know but i had one rattling round my junk bin, right on the edge of -10% tolerance but all that it's for is a voltage divider, so i've decided to try it.

EDIT: OK I've installed the new pot and triple checked the filter caps. Now i get a nice sharp trace on the screen and almost all is right with it that i can see EXCEPT i still got some popping from the capacitor area.

Now i'm sure they are in right i spent 6 hours just on them, the first pop was so loud i though a cap blew, none did.
The second pop was actually a set of them that  happened when i touched the spot adjust, but only the first time.
I was then able to adjust it and test the scope up to 2.5MHz (the highest my function generator goes) without issue.

Maybe the popping was just the sound of the dust bunnies committing suicide 

[Specmaster]

In that case you should be able to trace those wires from A to B and reconnect them to their correct locations. There's nothing to that scope is there, its very spartan

I wouldn't call 1600 volts and 400 some volts flying around the place nothing but then again i am a solid state guy, so far anyways.

The voltage is the main thing keeping me from just digging in, for fear of really screwing it up.

Hahaha, when I said there was nothing to that scope, I meant that I had watched Mr Carlsons video of that scope and by comparison to scopes of say 30 years ago, solid state as well which are completely rammed with electronics and voltages many times higher, it is empty. Being wired in a point to point fashion as it is, should make it easier to identify where things connect to because a component will be adjacent to the part it connects to. On a solid state system this is not always the case as it depends on how the designer can fit the pcb tracks in for miniaturisation purposes.

I was not in anyway belittling the voltages within the scope your working on. To have a healthy respect of voltage is good, no one should ever get complacent about working with high voltages because it can catch you out in an instant. I've been an engineer all my working life (retired now) and have had my share of shocks in that time even with being very careful.

That healthy regard will keep you in good stead for the future.

Sent from my SM-J510FN using Tapatalk

[Specmaster]

After a few hours of digging and taking out the filter caps to redo them i discover the cause of at least some of my problems. The 1 megohm pot for spot shape went completely round the bend at some point.
 Whether it was pre-existing or the result of a screw up i don't know but i had one rattling round my junk bin, right on the edge of -10% tolerance but all that it's for is a voltage divider, so i've decided to try it.

EDIT: OK I've installed the new pot and triple checked the filter caps. Now i get a nice sharp trace on the screen and almost all is right with it that i can see EXCEPT i still got some popping from the capacitor area.

Now i'm sure they are in right i spent 6 hours just on them, the first pop was so loud i though a cap blew, none did.
The second pop was actually a set of them that  happened when i touched the spot adjust, but only the first time.
I was then able to adjust it and test the scope up to 2.5MHz (the highest my function generator goes) without issue.

Maybe the popping was just the sound of the dust bunnies committing suicide 

If an filter cap blows, believe me when say that you will know about it, it will spill its guts for you. If you get one reversed they become very explosive and leave their contents all over place leaving you with a huge mess to clear up.

Sent from my SM-J510FN using Tapatalk

[bd139]

Indeed. It's Sunday and I'm bored so I blew up a capacitor for the sake of forum and my children's education

This is a tiddler. The big ones will take your hand off.

https://youtu.be/SE0SfHuzkaU

[Specmaster]

Indeed. It's Sunday and I'm bored so I blew up a capacitor for the sake of forum and my children's education

This is a tiddler. The big ones will take your hand off.

https://youtu.be/SE0SfHuzkaU

Impressive demonstration and as you rightly said, a big one is capable of taking your hand off should it be in the vicinity of it, even at a low voltage like 32V, you don't want to pick a fight with with it.

[bd139]

I’ll do a big one outside when it has warmed up a bit

Got a spare Epcos 2200uF 80v here which might be fun across the mains

[Specmaster]

I’ll do a big one outside when it has warmed up a bit

Got a spare Epcos 2200uF 80v here which might be fun across the mains

Theres loads of videos on youtube of large caps being blown up deliberately to show what a destructive force they are if misused 

Right, I'm off to Heathrow to collect Brother and Sister in Law on their return from Australia, I bet their going to be freezing when they disembark from the plane 

Catch you all later.

[bd139]

Yes but you have to experience it first hand 

Enjoy your visit to my polluted and noisy neck of the woods

[Fungus]

I usually do this on the final day of electronics class. 30V into a reversed 16V capacitor does the trick nicely.

Impressive demonstration and as you rightly said, a big one is capable of taking your hand off should it be in the vicinity of it, even at a low voltage like 32V, you don't want to pick a fight with with it.

Bigger ones often have better protection. If the cross on the end is properly stamped they just open up along the lines and a lot of nasty smoke comes out. No bang, more of a 'fut'.

[bd139]

I have some really old ones I have queued to blow up. Sprague and Plessey cans from the 1960s. Basically pipe bombs with legs. I’m doing a public service keeping them out of the hands of those insane restuffers!

[Specmaster]

Yes but you have to experience it first hand 

Enjoy your visit to my polluted and noisy neck of the woods

I already have at close quarters too, blew one up many moons ago it went off and I spent a long long time cleaning and decorating my parents living room to remove all the black gunk it deposited all over their nicely decorated walls and ceiling, to say nothing of the carpet. I never installed one backwards since I can tell you. 

Edit: I'm used to your noisy and polluted neck of the woods, Heathrow is no stranger to me, have been involved with many of the developments there for more years then I care to remember and I used to work for a company in Brentford directly below the flight path for over 18 years 

[Specmaster]

Not sure what the popping was that neo reported, if not caps then perhaps he has insulation issues with his mains transformer or something?

[neo]

Not sure what the popping was that neo reported, if not caps then perhaps he has insulation issues with his mains transformer or something?

i'm fairly sure a loose wire fell onto the grounded case. Either that or my dust bunny remark.

[Specmaster]

Not sure what the popping was that neo reported, if not caps then perhaps he has insulation issues with his mains transformer or something?

i'm fairly sure a loose wire fell onto the grounded case. Either that or my dust bunny remark.

Is it all working now then?

[neo]

Not sure what the popping was that neo reported, if not caps then perhaps he has insulation issues with his mains transformer or something?

i'm fairly sure a loose wire fell onto the grounded case. Either that or my dust bunny remark.

Is it all working now then?

So far at least, it really is amazing how much pandora a 1 meg ohm pot turned 5k ohm resistor can wreak.

[Specmaster]

Not sure what the popping was that neo reported, if not caps then perhaps he has insulation issues with his mains transformer or something?

i'm fairly sure a loose wire fell onto the grounded case. Either that or my dust bunny remark.

Is it all working now then?

So far at least, it really is amazing how much pandora a 1 meg ohm pot turned 5k ohm resistor can wreak.

Wow a 99.5% loss of resistance

[neo]

Wow a 99.5% loss of resistance

I believe thats what you would call a critical failure mode.

Either ways with the lack of a graticule i have no clue what i am going to do with this scope, i just like looking at it.

[Specmaster]

Keep watching Mr Carlson's Lab and he'll show you how to measure things with he said.

[Cerebus]

Indeed. It's Sunday and I'm bored so I blew up a capacitor for the sake of forum and my children's education

This is a tiddler. The big ones will take your hand off.

https://youtu.be/SE0SfHuzkaU

I had to wait for SWMBO to come home before I commented on this, why will become clear momentarily.

When I played this I almost thought I was listening to a recording of my own voice. I'm sure you all know the phenomenon where your own recorded voice sounds weird to yourself. Well, I played this for SWMBO and asked who she though the voice sounded like (with no priming as to what I was thinking) - she immediately named me. So, not only does your own voice sound 'wrong' when it's recorded, the recorded voice of someone else who sounds reasonably like you sounds 'wrong' to you in the same way too.

What I hear when I listen to myself recorded, and now also a recorded BD139, is something that almost borders on the adenoidal, quite nasal sounding and much higher pitched than my internal perception. Objective third parties say my voice has neither of those characteristics and is quite low pitched. I wonder if: (1) BD139 perceives his own recorded voice in the same way that I do mine, (2) what we'd sound like to each other face-to-face as opposed to a recording, (3) if we could get away with providing vocal alibis for each other?

[Specmaster]

Indeed. It's Sunday and I'm bored so I blew up a capacitor for the sake of forum and my children's education

This is a tiddler. The big ones will take your hand off.

https://youtu.be/SE0SfHuzkaU

I had to wait for SWMBO to come home before I commented on this, why will become clear momentarily.

When I played this I almost thought I was listening to a recording of my own voice. I'm sure you all know the phenomenon where your own recorded voice sounds weird to yourself. Well, I played this for SWMBO and asked who she though the voice sounded like (with no priming as to what I was thinking) - she immediately named me. So, not only does your own voice sound 'wrong' when it's recorded, the recorded voice of someone else who sounds reasonably like you sounds 'wrong' to you in the same way too.

What I hear when I listen to myself recorded, and now also a recorded BD139, is something that almost borders on the adenoidal, quite nasal sounding and much higher pitched than my internal perception. Objective third parties say my voice has neither of those characteristics and is quite low pitched. I wonder if: (1) BD139 perceives his own recorded voice in the same way that I do mine, (2) what we'd sound like to each other face-to-face as opposed to a recording, (3) if we could get away with providing vocal alibis for each other?

Wow, are you sure from East London, sounds more like Brentwood to me does that. 

[Specmaster]

Sod it, thats the first 2 items on my Ebay watch list nicked from under my nose at the last second, I wonder if it's set a trend for the next 4 items then 

[ChrisLX200]

Sod it, thats the first 2 items on my Ebay watch list nicked from under my nose at the last second, I wonder if it's set a trend for the next 4 items then 

Wouldn't be Agilent PSUs or Decade resistance boxes would it?

[Specmaster]

Sod it, thats the first 2 items on my Ebay watch list nicked from under my nose at the last second, I wonder if it's set a trend for the next 4 items then 

Wouldn't be Agilent PSUs or Decade resistance boxes would it?

Nope, you're in the clear there.

[neo]

First there was the Heathkit which was a bit of a project, and then there was a Hickok 209A that was easy street in comparison.

Also i think the Hickok may well be in the running for the world's largest panel meter, or barring that the largest VTVM. It was top of the line for the day and age (50s? the serial number suggest 1943 but i don't believe it.) with capacitance, inductance, decibels, ohms, AC and DC.
It is massive, and i do mean massive you could store a pound of coffee and week's rations in the case, and i own two of them.