Author Topic: Smoke und fire after switching on old electronics TEK DSA 602  (Read 7787 times)

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Offline Physikfan

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Smoke und fire after switching on old electronics TEK DSA 602
« on: August 08, 2017, 07:31:02 pm »
Hello friends of electronics

A dealer for used electronics supplied me two Tektronix 11000 oscilloscope frames, DSA 602 and DSA 602A.
I was of the opinion that the devices were checked at least once before delivery.
I switched on the devices in a large exhibition hall to test the frames and some 11000`s like 11A72 etc.
That was not very smart.
After approximately 5 to 10 minutes after switching on, one of the devices worked electrically initially faultlessly, biting smoke came out from both devices, which greatly influenced the air quality in the exhibition hall.
Even one of these devices started to burn inside.
After extinguishing the fire, the dealer agreed not to have checked the equipment before loading.

However, every experienced electronics engineer should know that one should deal very carefully with a very long time of unused HP and Tektronix devices.
You should first connect these devices to a variable mains supply and the full mains voltage should applied step by step only after 2-5 minutes, in order to re-form various capacitors and to avoid potential explosions etc.

I would be interested in whether someone has already had similar experiences with smoke and fire when switching on old electronics.

The only positive thing followed this action was a corresponding price reduction.

I will present some pictures of the damaged parts soon.

I hope I get from you also some hints how to repair these devices.
The documentation of the Tek devices is unfortunately not sufficient in the 11000 series, in contrast to the 7000 series.

Best regards

Physikfan
« Last Edit: August 18, 2017, 10:57:42 am by Physikfan »
 

Online bd139

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Re: Smoke und fire after switching on old electronics
« Reply #1 on: August 08, 2017, 07:36:19 pm »
Sounds like mains filters. Many a time have I filled up my living room with the guts of them. They make a right mess inside the kit.
 
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Offline alm

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Re: Smoke und fire after switching on old electronics
« Reply #2 on: August 08, 2017, 07:54:52 pm »
However, every experienced electronics engineer should know that one should deal very carefully with a very long time of unused HP and Tektronix devices.
You should first connect these devices to a variable mains supply and the full mains voltage should applied step by step only after 2-5 minutes, in order to re-form various capacitors and to avoid potential explosions etc.
This was recently discussed on the TekScopes Yahoo! group. A variac does not do much for capacitor reforming, since it will not limit the current, and can kill some switching power supplies without a good under voltage lockout. It also defeats any time delay that old power supplies may have. If you want to reform caps, take them out and feed them from a power supply limited to a low current. I would do good visual inspection for loose wires, burnt parts or loose screws/foreign bodies. Also check any voltage selection (internal jumpers or external switches) and correct fuse ratings (check if some idiot found a suitably sized bolt that fit the fuse holder). Apart from that, just turn it on and hope for the best.

I would be interested in whether someone has already had similar experiences with smoke and fire when switching on old electronics.
My first suspicion would be X-caps (Rifa?) in the power supply input filter. Assuming these scopes have them.
 

Online bd139

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Re: Smoke und fire after switching on old electronics
« Reply #3 on: August 08, 2017, 08:10:33 pm »
Every time I hear RIFA or Schaffner I dive under the table and don the gas mask :)
 
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Offline bitseeker

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Re: Smoke und fire after switching on old electronics
« Reply #4 on: August 08, 2017, 10:50:17 pm »
Every time I hear RIFA or Schaffner I dive under the table and don the gas mask :)

Yes! Beware of the excessively dynamic duo.
I TEA.
 

Online amyk

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Re: Smoke und fire after switching on old electronics
« Reply #5 on: August 09, 2017, 02:10:33 am »
Those mains filter caps are more likely to turn into smoke bombs than other regular caps, which either silently dry out to the point of being useless or go out with a short pop.
 

Offline GreyWoolfe

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Re: Smoke und fire after switching on old electronics
« Reply #6 on: August 10, 2017, 12:47:41 am »
Oh, yes.  A couple of years ago, someone gave me a Tektronix tube scope, I can't remember model.  I didn't have a variac then so, foolishly, I plugged it in and turned it on.  Almost immediately, something popped, smoke and a tendril of flame erupted.  The smell was memorable and it lingered for a day or so.  SWMBO wasn't happy with me, she made me put it on the curb for pickup. 
"Heaven has been described as the place that once you get there all the dogs you ever loved run up to greet you."
 

Online bd139

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Re: Smoke und fire after switching on old electronics
« Reply #7 on: August 10, 2017, 07:20:06 am »
SWMBO at this location casually walks over to the window now, opens it, sticks her head out and carries on with her business as usual until the smoke has cleared ;D
 

Offline GreyWoolfe

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Re: Smoke und fire after switching on old electronics
« Reply #8 on: August 10, 2017, 12:26:20 pm »
SWMBO at this location casually walks over to the window now, opens it, sticks her head out and carries on with her business as usual until the smoke has cleared ;D

My office is an extension on the back of the house that the original owners built.  She doesn't like coming out into the office, she says it's intimidating out here.  I can't understand why.  Just because there is my company laptop with dual displays, my personal computer with dual displays, my workbench with all kinds of electronics devices on it with a 32" TV as a monitor, all the network equipment and everything else (storage shelves), I don't see what is intimidating about it. >:D  She usually just closes the sliding glass door.  However, that day the door was open and she wasn't home at the time of the incident.  Add to the fact that she is practically allergic to air and almost any smell aggravates her sinuses, it explains why I got into trouble.
"Heaven has been described as the place that once you get there all the dogs you ever loved run up to greet you."
 

Offline Kjelt

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Re: Smoke und fire after switching on old electronics
« Reply #9 on: August 10, 2017, 01:05:30 pm »
Yup one of the mainsfilter capacitor of my old Philips scope also turned itself into a lot of toxic smoke and I used it around 8 months or so before, so this failure can just happen when the capacitor thinks its his time.

 

Online bd139

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Re: Smoke und fire after switching on old electronics
« Reply #10 on: August 10, 2017, 01:11:05 pm »
My last two explosions were Philips scopes. The thing that gets me is you crank the things up on the mains and let them bed in for a few minutes and just as the worrying dies down and you have some confidence in it. Just when you're relaxing it is followed by pssssssssssssssssssssssssssss phut!

SWMBO at this location casually walks over to the window now, opens it, sticks her head out and carries on with her business as usual until the smoke has cleared ;D

My office is an extension on the back of the house that the original owners built.  She doesn't like coming out into the office, she says it's intimidating out here.  I can't understand why.  Just because there is my company laptop with dual displays, my personal computer with dual displays, my workbench with all kinds of electronics devices on it with a 32" TV as a monitor, all the network equipment and everything else (storage shelves), I don't see what is intimidating about it. >:D  She usually just closes the sliding glass door.  However, that day the door was open and she wasn't home at the time of the incident.  Add to the fact that she is practically allergic to air and almost any smell aggravates her sinuses, it explains why I got into trouble.

You should buy her a gas mask :D
 

Offline Kjelt

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Re: Smoke und fire after switching on old electronics
« Reply #11 on: August 10, 2017, 01:15:34 pm »
My last two explosions were Philips scopes. The thing that gets me is you crank the things up on the mains and let them bed in for a few minutes and just as the worrying dies down and you have some confidence in it. Just when you're relaxing it is followed by pssssssssssssssssssssssssssss phut!

:) the worst thing actually which I am quite  :-[ to say, a friend of mine warned me a year ago to preventively replace that capacitor..... yeah postponing is not always the smartest thing to do.
All old Philips scope owners: I warned you  >:D
 

Offline schmitt trigger

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Re: Smoke und fire after switching on old electronics
« Reply #12 on: August 10, 2017, 01:21:25 pm »
In the old days, with iron powerline transformers, it was customary for one to use a Variac and turn it up s--l--o--w--l--y.

Nowadays, if the units have a SMPS, then slowly ramping the supply will cause it to "hiccup"...depending on the design it could cause it to become damaged.
 

Offline alm

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Re: Smoke und fire after switching on old electronics
« Reply #13 on: August 10, 2017, 01:29:27 pm »
How well did Variacs work with time-delay circuits used in old tube equipment to allow the tubes to warm-up before applying power to the resit of the circuit?
 

Online bd139

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Re: Smoke und fire after switching on old electronics
« Reply #14 on: August 10, 2017, 01:36:54 pm »
Variacs were only really very good for doing line voltage regulation tests if you ask me. Stuff still explodes when you ramp the voltage and there's something wrong either way.  My variac can handle 8A without blowing up as an example! That's going to kill anything you connect to it. I've seen a lot of people sticking an incandescent lamp in series with a device. That makes more sense as the thing will light up if there's something wrong before the magic smoke comes out of the DUT.

Really though; knowledge of this issue, inspection, measurement, safety goggles. Most modern devices you can spot explosions risks i.e. cracked and leaky caps and anything with the word Schaffner on it.
 

Offline Rbastler

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Re: Smoke und fire after switching on old electronics
« Reply #15 on: August 10, 2017, 01:46:46 pm »
None of my tube gear does have a time delay after it switches the rest on. Or more correct would be to say, that for those with a rectifier tube that time delay is already included, by working when heatet up, like the rest.
This is actually the only time I used a variac, so I woudnt shock the tubes filament. Didn't bother for semiconductor gear. Wy would you do it ?
I too had a mains filter cap in my PE1540 dying with a pffffff-tsch, while performing a load test.


Edit: I used a incandeshend lamp as a short detection, when I repaired tube radios. Works like a charm.
« Last Edit: August 10, 2017, 01:48:34 pm by Rbastler »
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Gamma spectrometer works. Now some yellow crystals need regenerating and testing.
 

Offline nanofrog

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Re: Smoke und fire after switching on old electronics
« Reply #16 on: August 10, 2017, 02:09:45 pm »
She usually just closes the sliding glass door.  However, that day the door was open and she wasn't home at the time of the incident.  Add to the fact that she is practically allergic to air and almost any smell aggravates her sinuses, it explains why I got into trouble.
Have her try Zyrtec (OTC now & there's even generics); if her sinuses get plugged up, opt for Zyrtec-D.  ;) Works like a charm for me.  If she won't take it, do like giving a pill to a dog; put it in her food.  :o  :-DD

You might want to try using a 100W incandescent bulb in series on the Line/Hot wire when turning on old equipment as it will limit the current (too much current draw, and the bulb blows). Super simple, inexpensive, and it works.  ;)

 

Offline alm

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Re: Smoke und fire after switching on old electronics
« Reply #17 on: August 10, 2017, 02:26:13 pm »
How would a mains-rated bulb blow from being put in series with a short?
 

Offline Rbastler

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Re: Smoke und fire after switching on old electronics
« Reply #18 on: August 10, 2017, 02:28:52 pm »
It woudnt. Just limit the current. Comes with free short/too much current indicator :D

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Offline nanofrog

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Re: Smoke und fire after switching on old electronics
« Reply #19 on: August 10, 2017, 02:58:53 pm »
How would a mains-rated bulb blow from being put in series with a short?
Bulb filament acts as a fuse (too much current, and it pops/vaporizes as it's over-heated). The bulb brightness also acts as an indicator; the brighter the bulb, the more severe the problem.
 

Online Gyro

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Re: Smoke und fire after switching on old electronics
« Reply #20 on: August 10, 2017, 03:36:02 pm »
It doesn't act as a fuse, it acts as a PTC thermistor. It won't pop because worst case it will see normal mains voltage.
Chris

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Offline GreyWoolfe

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Re: Smoke und fire after switching on old electronics
« Reply #21 on: August 11, 2017, 11:53:28 am »
She usually just closes the sliding glass door.  However, that day the door was open and she wasn't home at the time of the incident.  Add to the fact that she is practically allergic to air and almost any smell aggravates her sinuses, it explains why I got into trouble.
Have her try Zyrtec (OTC now & there's even generics); if her sinuses get plugged up, opt for Zyrtec-D.  ;) Works like a charm for me.  If she won't take it, do like giving a pill to a dog; put it in her food.  :o  :-DD

You might want to try using a 100W incandescent bulb in series on the Line/Hot wire when turning on old equipment as it will limit the current (too much current draw, and the bulb blows). Super simple, inexpensive, and it works.  ;)



Benadryl is her friend but it makes her sleepy.  Zyrtec is not reliable enough.  When the allergies act up bad enough she gets her boss to write her a proper prescription.  I have made a dim bulb tester.  I found a neat example on the web that uses a modified switched outlet and everything is i a plastic dual junction box.  I didn't have it back then.
"Heaven has been described as the place that once you get there all the dogs you ever loved run up to greet you."
 

Offline Physikfan

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Re: Smoke und fire after switching on old electronics
« Reply #22 on: August 11, 2017, 02:38:10 pm »
Pictures of the damaged DSA602:



DSA602


Power supply from the side


Power supply from the rear


Rear of rear cover plate


smoked components

I am looking forward to your comments
 

Online bd139

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Re: Smoke und fire after switching on old electronics
« Reply #23 on: August 11, 2017, 03:05:38 pm »
That's definitely mains filter. You can tell by the brown stains. Quite a lot of damage. Write off IMHO.

It'll probably be fine if you can get a replacement supply and clean up the chassis though.
« Last Edit: August 11, 2017, 03:07:51 pm by bd139 »
 

Offline Physikfan

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Re: Smoke und fire after switching on old electronics
« Reply #24 on: August 11, 2017, 07:27:50 pm »
Images of parts of the smoking and burning DSA602A:


Power supply board with defective filter X2


Filter X2 in detail, this component burned.
This board looks better than the non-firing board of the DSA402.

I am looking forward to your comments.
« Last Edit: August 11, 2017, 07:35:53 pm by Physikfan »
 


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