Test Equipment Anonymous (TEA) group therapy thread

[AVGresponding]

Gah, bloody packing chips, the damn things get everywhere.

It is the counter, for some reason I thought it was full rack width, where it's actually half width.

Time to take it apart...   

[mnementh]

Bah, trawling through the wholesalers sites looking for RIFA replacements, hard to find a single supplier for all the values I want.   

I'm thinking to use some Y caps instead of X caps for some values, should be ok, right?

You can subsitute a Y for an X but NOT an X in place of a Y.
Y class are used were a failure could cause a risk of shock e.g. live to ground. While the marked "rated" voltage of a Y may be  the same as a X the surge and test voltages are higher as is reliability for the Y.

For those playing along at home: Y-class are designed such that when they fail, they fail open. Most of the time. Big difference in the safety factor there, as line voltages are present.

mnem
 

[AVGresponding]

Quick question for the nixie experts:

What's the purpose of a loose mounting metal mesh, fitting between the display filter, and the outer screen?

[McBryce]

Quick question for the nixie experts:

What's the purpose of a loose mounting metal mesh, fitting between the display filter, and the outer screen?

How do you mean? There's the mesh at the front, that's the Anode and the numbers are the cathodes.

McBryce.

[Robert763]

Bah, trawling through the wholesalers sites looking for RIFA replacements, hard to find a single supplier for all the values I want.   

I'm thinking to use some Y caps instead of X caps for some values, should be ok, right?

You can subsitute a Y for an X but NOT an X in place of a Y.
Y class are used were a failure could cause a risk of shock e.g. live to ground. While the marked "rated" voltage of a Y may be  the same as a X the surge and test voltages are higher as is reliability for the Y.

For those playing along at home: Y-class are designed such that when they fail, they fail open. Most of the time. Big difference in the safety factor there, as line voltages are present.

mnem
 

See Reply #81265
How do you design a capacitor to fail open instead of short? (notwithstanding that many do e.g. Sprague, but that is not by design)

[Kosmic]

Bah, trawling through the wholesalers sites looking for RIFA replacements, hard to find a single supplier for all the values I want.   

I'm thinking to use some Y caps instead of X caps for some values, should be ok, right?

You can subsitute a Y for an X but NOT an X in place of a Y.
Y class are used were a failure could cause a risk of shock e.g. live to ground. While the marked "rated" voltage of a Y may be  the same as a X the surge and test voltages are higher as is reliability for the Y.

For those playing along at home: Y-class are designed such that when they fail, they fail open. Most of the time. Big difference in the safety factor there, as line voltages are present.

mnem
 

See Reply #81265
How do you design a capacitor to fail open instead of short? (notwithstanding that many do e.g. Sprague, but that is not by design)

I guess this is what Kemet call Self-Healing 



https://sh.kemet.com/Lists/FileStore/EvoxRifaRFIandSMD.pdf

[nixiefreqq]

Quick question for the nixie experts:

What's the purpose of a loose mounting metal mesh, fitting between the display filter, and the outer screen?

How do you mean? There's the mesh at the front, that's the Anode and the numbers are the cathodes.

McBryce.

i think he is talking about the EMI screen sometimes found on the Mil versions?

[mnementh]

Just to make bd cry: Destructively dismantling a perfectly good inductor to get ~1/2m of hookup wire.

BWAHAHAHAHAHA!!!

mnem
 

[mnementh]

Bah, trawling through the wholesalers sites looking for RIFA replacements, hard to find a single supplier for all the values I want.   

I'm thinking to use some Y caps instead of X caps for some values, should be ok, right?

You can subsitute a Y for an X but NOT an X in place of a Y.
Y class are used were a failure could cause a risk of shock e.g. live to ground. While the marked "rated" voltage of a Y may be  the same as a X the surge and test voltages are higher as is reliability for the Y.

For those playing along at home: Y-class are designed such that when they fail, they fail open. Most of the time. Big difference in the safety factor there, as line voltages are present.

mnem
 

See Reply #81265
How do you design a capacitor to fail open instead of short? (notwithstanding that many do e.g. Sprague, but that is not by design)

Sorry, I'm not that kind of engineer. Ask the people who designed them. I'm repeating what I've read from the product lit and numerous engineering websites.

I figure it's like the way a lumberjack cuts a tree so he knows which way it's gonna fall... most of the time.

mnem
 

[bd139]

Quick question for the nixie experts:

What's the purpose of a loose mounting metal mesh, fitting between the display filter, and the outer screen?

Usually RF shielding. The discharge process is RF noisy.

[bd139]

Just to make bd cry: Destructively dismantling a perfectly good inductor to get ~1/2m of hookup wire.

BWAHAHAHAHAHA!!!

mnem
 

You can’t get me with that one. The ghosts of a thousand HT transformers follow me everywhere. 

[mnementh]

LOLOL!

mnem
   *tsssst...*

[AVGresponding]

Thanks all for the replies on the mesh.

Seeing as I phoned in sick today I have time to do a teardown post, which will clarify things I think:

Here's the front panel. You can't really see from this, but there's some distortion in the display:


When I took the casing off, these labels fluttered out:


Under the lid, we can see one of the nixies has been replaced, and also its driver IC, now also socketed:


I've never seen a design like this before. I presume there's a purpose, better thermal dissipation perhaps?


Here's its 5MHz reference, which has a tweaking pot on the back of it:


Grrr, gorillas at work:


Here's the underside of the (only) main board, none of that solder mask rubbish here:


Interestingly the back of the board is clearly designed as an edge connector. Perhaps the board is a modular component that fits in a mainframe type unit as well? The blue colouring on the screws is anodisation, not corrosion.


Ugh what a filthy hole:


Duraglit/Brasso to the rescue:


Here's the display filter and that metal mesh I mentioned:


And finally, the money shot:


Some of the numbers on digits two and six are slow to illuminate, not sure if it's a driver issue, or the tubes themselves?

[BU508A]

Should be easy to find out: exchage the tubes.

[AVGresponding]

Should be easy to find out: exchage the tubes.

I'd have to take out the display driver board, and desolder them; they aren't socketed (those black plastic frames are just stabilisers I believe).
It's not important enough for that kind of effort.

[Saskia]

seems I am a Brexit victim. The probe is still stuck in customs ...

[Robert763]

Bah, trawling through the wholesalers sites looking for RIFA replacements, hard to find a single supplier for all the values I want.   

I'm thinking to use some Y caps instead of X caps for some values, should be ok, right?

You can subsitute a Y for an X but NOT an X in place of a Y.
Y class are used were a failure could cause a risk of shock e.g. live to ground. While the marked "rated" voltage of a Y may be  the same as a X the surge and test voltages are higher as is reliability for the Y.

For those playing along at home: Y-class are designed such that when they fail, they fail open. Most of the time. Big difference in the safety factor there, as line voltages are present.

mnem
 

See Reply #81265
How do you design a capacitor to fail open instead of short? (notwithstanding that many do e.g. Sprague, but that is not by design)

I guess this is what Kemet call Self-Healing 



https://sh.kemet.com/Lists/FileStore/EvoxRifaRFIandSMD.pdf

Self healing is not the same thing. It inherntly relies on the current flowing through the short to vaporise the metalisation. If there is no high current path the capacitor remains shorted. An example is the "Y" capacitor across the isolation barrier in many double insulated SMPSUs. If that fails in the case of a laptop for example the chassis of th laptop is live and can pass enough current to cause a shock. The RIFA PME271 is self healing and we all know that they don't fail open circuit! http://www.farnell.com/datasheets/1886898.pdf

[Specmaster]

Ditto. And you would be surprised how many Americans, even folks my age, have absolutely no clue how to drive a manual gearbox. Present a typical driver with a vehicle with 3 pedals and it's total panic. Automatic transmissions really started to take over in the 1960's and many folks never had to drive a stick and never learned.

I had a friend teach me to drive a manual in the late 70's.  I didn't have my first manual car until the late 80's, a 1980 Toyota Tercel hatchback.  Both Mrs GreyWoolfe (55) and I(64) can drive manuals.  I find them fun to drive outside of occasionally getting caught in traffic jams.  My 92 Ford Explorer had a rather heavy clutch and Mrs GreyWoolfe didn't much like driving it for that reason but I enjoyed the beast.  I had a 2001 Chevy Cavalier almost from new and put 100,000 miles on it in 2.5 years.  It was easy to drive without using the clutch for anything but first.  I only did it to show off and prove it can be done to non believers.  Of the 3 manual cars I have owned over the years, I miss the Explorer the most.

Yes, I used to drive buses (with no passengers, not licensed for passengers) and like you, only needed the clutch to pull away in first and for stopping, other gear changes were done without a clutch and those buses had the crashboxes where you had double clutch on changing down gears. It took a lot of practise to get them sweet with no grinding but I was taught by a master of it.

[Specmaster]

Woot! Amazon has just delivered my calculator kit, only 2 days late thats all 

[bd139]

Self healing is not the same thing. It inherntly relies on the current flowing through the short to vaporise the metalisation. If there is no high current path the capacitor remains shorted. An example is the "Y" capacitor across the isolation barrier in many double insulated SMPSUs. If that fails in the case of a laptop for example the chassis of th laptop is live and can pass enough current to cause a shock. The RIFA PME271 is self healing and we all know that they don't fail open circuit! http://www.farnell.com/datasheets/1886898.pdf

The RIFAs, as all of them, only self heal a finite number of times. Once all the dielectric is blown through then there's not much capacitor left so you end up passing current through all the deposited oxides etc. This turns into a nice stinky resistor.

The RIFAs were just particularly bad because of the encapsulation issues which are supposedly because they were slightly hygroscopic.

At the end of the day these are sacrificial components with a finite design life. Replace 'em every 5-10 years and move on. Nothing lasts forever

[bd139]

seems I am a Brexit victim. The probe is still stuck in customs ...

I'm a UPS + Brexit victim this week. The package that contained the motherboard I sold on ebay disappeared inside Stanford-le-hope UPS terminal which is clogged up with brexit customs shit unfortunately. I didn't know this but apparently UPS consider a parcel to be lost if it disappears for 72 hours.

Just a note to save people pain as well: if you're going to sell stuff through ebay, DO NOT use Packlink. They are a Spanish company who are impossible to sue and do not respond to you when you place a claim. Only deal directly with the courier in question as you have a contract with them directly then and can claim directly.

[McBryce]

Should be easy to find out: exchage the tubes.

I'd have to take out the display driver board, and desolder them; they aren't socketed (those black plastic frames are just stabilisers I believe).
It's not important enough for that kind of effort.

Check what voltage they are getting, slow lighting can be due to the voltage being too low.

McBryce.

[med6753]

Mid-day and supposed to continue well into tonight and early AM Tuesday. Luckily it's a dry powder since the temp is -8 C. Which means poor packing for snowmen. 

 

[Kosmic]

Mid-day and supposed to continue well into tonight and early AM Tuesday. Luckily it's a dry powder since the temp is -8 C. Which means poor packing for snowmen. 

Apparently it's coming over here. Should start tomorrow.

[Kosmic]

For my fellow Canadians, there's a nice HP 1137A high voltage probe for sale near Toronto (not my listing).

https://www.kijiji.ca/v-view-details.html?adId=1548925348