Blew Up My First Oscilloscope!!!

[PixieDust]

 

Woops, not sure what happened. I was going through the first chapter of my oscilloscope manual and all of a sudden I heard frying/sizzling and then a tonne of magic smoke (I'm guessing a large capacitor). (It was still working while I was pulling the power chord out).

The only thing that I didn't do according to the manual was have probes inserted. But no measurements were even required up to this point in time. The manual was mostly just going through using all the menus and knobs and buttons.

The frying happened when I got to the section of triggering (went though some basic things in Vertical and Horizontal controls). After pressing Auto, I pressed the Trigger->Mode button and then I cycled through the various modes and then boom!

What on earth happened? Anyone have any ideas?

[ataradov]

Most likely not your fault. This is an old device, capacitors are all dried up by now.

Disassemble it and see what exactly is blown.

[DaJMasta]

Yep, no input on the front and it's quite unlikely it was you.  Most likely adjusting the controls was coincidental, but maybe a setting turned on something which was not happy to be on.  The next step is definitely to sniff around and find the smoked bit.

[Ice-Tea]

Unless you ignored a voltage selector at the back (or the rating itself) most likely not your fault..

[Keicar]

Schaffner line filter perhaps?

[Fungus]

Woops, not sure what happened.

It's old. Probably some component teetering on the brink that just happened to die while you were touching the front panel.

[PixieDust]

Thanks guys, will sniff around a bit. Smells like burn wood, doesn't smell chemically. I thought it might be dust, but when I opened it, there wasn't much dust to be found. Most of the unit is relatively clean. There was dust in spots, but none of it looked burnt.

I certainly didn't mess up the voltage rating .

I'll look for damaged capacitors or Schaffner filter.

[med6753]

RIFA capacitor on the primary most likely.

[VK5RC]

Don't forget Tektronix's excellent fault finding in a oscilloscope paper - from the 70s
Edit' couldn't get the ######  link to work (on a phone)
Google Tektronix Oscilloscope Troubleshooting
Apol, Rob

[PixieDust]

RIFA capacitor on the primary most likely.

Looks like we have a winner. You guys are too good.

Don't forget Tektronix's excellent fault finding in a oscilloscope paper - from the 70s https://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf&ved=2ahUKEwjDm-CG49vgAhXJfH0KHRmXD4wQFjAGegQIARAB&usg=AOvVaw33-ERYv-GmqJm7WWiDgvoo

That link doesn't work for me?

[Wolfgang]

As there is no crater in your desk its probably a lighter case. I would bet on wearout rather than misuse. 

[HalFET]

Don't forget Tektronix's excellent fault finding in a oscilloscope paper - from the 70s https://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf&ved=2ahUKEwjDm-CG49vgAhXJfH0KHRmXD4wQFjAGegQIARAB&usg=AOvVaw33-ERYv-GmqJm7WWiDgvoo

That link doesn't work for me?

Try it without the "&..." part: https://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf 

[lordvader88]

I just learned what RIFA caps are myself, and I have a Tek 2430A scope. I had it apart before, when I knew a lot less. Soon I should take it apart again and have a nice look around. Same with my Tek2215

[tggzzz]

I just learned what RIFA caps are myself, and I have a Tek 2430A scope. I had it apart before, when I knew a lot less. Soon I should take it apart again and have a nice look around. Same with my Tek2215

Those delayed action smoke generators are in many many pieces of equipment of that era. They should be replaced, and replaced on sight if there is any cracking in the transparent outer case.

They are also buried inside many IEC connector mains filters, especially Schaffner filters.

[PixieDust]

I just learned what RIFA caps are myself, and I have a Tek 2430A scope. I had it apart before, when I knew a lot less. Soon I should take it apart again and have a nice look around. Same with my Tek2215

This is what happens if you don't:



Exactly what happened to me, was on for about 10 minutes and then started smoking like a chimney!

They are also buried inside many IEC connector mains filters, especially Schaffner filters.

Thanks for the heads up.

According to Dave's video:



They can look fine after they go. But I think that's the case if you pull the plug quickly. Mine were sizzling for a good 5-7 seconds. Then it becomes apparent that something is wrong because there's more time to do damage.

[tooki]

What amazes me is that Kemet is still manufacturing those awful things. (Kemet bought up Evox-Rifa years ago.)

For example, here’s the datasheet for the exact series shown in the preview of Dave’s video above: http://www.kemet.com/Lists/ProductCatalog/Attachments/322/KEM_F3011_PME271M_X2_275.pdf

Like... ugh.

[David Hess]

Schaffner line filter perhaps?

Or the paper-film RIFA X and Y capacitors.

[tooki]

Schaffner line filter perhaps?

Or the paper-film RIFA X and Y capacitors.

You’re about a day late. It was already confirmed to be those, hence the ensuing discussion of them.

[james_s]

What amazes me is that Kemet is still manufacturing those awful things. (Kemet bought up Evox-Rifa years ago.)

For example, here’s the datasheet for the exact series shown in the preview of Dave’s video above: http://www.kemet.com/Lists/ProductCatalog/Attachments/322/KEM_F3011_PME271M_X2_275.pdf

Like... ugh.

Perhaps they have been improved?

Also it's worth noting that the ones that are failing now are mostly more than 20 years old, while not ideal I have a hard time being upset over 20+ year old components failing. I had one burn up in the power supply of an Apple IIe years ago, it made a bunch of stinky smoke but it didn't really cause any collateral damage.

[Zenith]

Here are two Rifa 2200pF Y class capacitors which are probably over 20 years old, but are unused and have been kept in reasonable conditions.  Both are cracked in the same place. The crack underlines the Rifa logo and goes up just short of the corners and there's a similar crack on the back. It looks to be an age related thing.

There are loads of X and Y rated capacitors of the same age which don't have this class fault.

[james_s]

Well I'm not arguing that they're the best or anything but they're still old. It's unknown whether the currently manufactured ones will exhibit the same fault, one can hope they've been improved.

[duak]

Some 2200 series scopes also have problems with some 470K or so 1/4 W resistors in the focus circuit.  If the the scope is apart, look for a group of  resistors with a bit of space around them.  The PCB itself might also look a bit stressed.  If I remember correctly, Tek used 5 or so of them in series to handle a 1 KV or so potential.

Cheers,

[tooki]

What amazes me is that Kemet is still manufacturing those awful things. (Kemet bought up Evox-Rifa years ago.)

For example, here’s the datasheet for the exact series shown in the preview of Dave’s video above: http://www.kemet.com/Lists/ProductCatalog/Attachments/322/KEM_F3011_PME271M_X2_275.pdf

Like... ugh.

Perhaps they have been improved?

Also it's worth noting that the ones that are failing now are mostly more than 20 years old, while not ideal I have a hard time being upset over 20+ year old components failing. I had one burn up in the power supply of an Apple IIe years ago, it made a bunch of stinky smoke but it didn't really cause any collateral damage.

Valid points to be sure, and I did consider that (somewhat) without mentioning it before.

My hunch, though, is that they haven't been changed, or else they'd have changed the part number.

Here are two Rifa 2200pF Y class capacitors which are probably over 20 years old, but are unused and have been kept in reasonable conditions.  Both are cracked in the same place. The crack underlines the Rifa logo and goes up just short of the corners and there's a similar crack on the back. It looks to be an age related thing.

There are loads of X and Y rated capacitors of the same age which don't have this class fault.

The local mom-and-pop electronics store/living museum has bins of Rifa caps that are cracked, for sale. o_O

[JohnPen]

High value Resistors with high voltages across them used to be a problem with the old CRT TV years ago.  The focus potential used a chain of high value carbon resistors, often in the Megohm range, and they used to shift dramatically in value as they aged.  Sometimes down by several Megs other times similarly upwards.  High voltages across resistors, particularly the carbon based ones,  are definitely not very good for them.

[Zenith]

[]Valid points to be sure, and I did consider that (somewhat) without mentioning it before.

My hunch, though, is that they haven't been changed, or else they'd have changed the part number.

They caused no problems whatsoever for the OEM or the first owner.

The manufacturer didn't find they caused production rework or warranty claims.

The first owner wasn't likely to keep the unit for more than ten years, and there weren't many post warranty problems, which the maker wouldn't particularly want.

Rifa had a successful product which they'd had to pay to have certified with UL and the rest.

No one, who mattered, cared what was going to happen 12 years plus down the line, and probably still doesn't.