EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Physikfan on August 08, 2017, 07:31:02 pm
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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
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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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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.
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Every time I hear RIFA or Schaffner I dive under the table and don the gas mask :)
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Every time I hear RIFA or Schaffner I dive under the table and don the gas mask :)
Yes! Beware of the excessively dynamic duo.
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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.
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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.
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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
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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.
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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.
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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
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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
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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.
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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?
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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.
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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.
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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. ;)
(http://i.imgur.com/EtClrJt.jpg)
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How would a mains-rated bulb blow from being put in series with a short?
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It woudnt. Just limit the current. Comes with free short/too much current indicator :D
Sent from my A0001 using Tapatalk
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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.
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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.
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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. ;)
(http://i.imgur.com/EtClrJt.jpg)
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.
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Pictures of the damaged DSA602:
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0001400x270.jpg)
DSA602
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0008400x254.jpg)
Power supply from the side
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0011400x313.jpg)
Power supply from the rear
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0013400x543.jpg)
Rear of rear cover plate
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0015400x305.jpg)
smoked components
I am looking forward to your comments
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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.
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Images of parts of the smoking and burning DSA602A:
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0089400x295.jpg)
Power supply board with defective filter X2
(http://galerie.experimentierkasten-board.de/data/media/201/_MG_0098400x190.jpg)
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.
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Yep RIFA X2. Well know flame throwers. Hit google images and search for "RIFA X2 explode".
Desolder it, clean the board up with IPA carefully and damage assess. If nothing is damaged, bring the supply up without it still installed and see if it works. That badly burned one is a write off.
I'd advise getting on the cleaning pretty quick as that goop sets like concrete after a couple of weeks.
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Hi bd139
Please what do you mean with IPA, iso-propyl-alcohol?
Regards
Physicfan
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Yes that's it :)
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What is the proactive treatment for this issue?
I have two of these on my bench that I fire up and use at least twice a week.
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Proactive treatment is to replace them if they're old. The first visible signs of impending doom are small cracks developing in the transparent/translucent outer casing.
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That's all you need to do. The cheap Chinese X2 rated ones are fine as replacements.
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Images of parts of the DSA602:
(http://galerie.experimentierkasten-board.de/data/media/201/DSA602damagedfilterremoved400x267.jpg)
Defective component removed
(http://galerie.experimentierkasten-board.de/data/media/201/DSA602Filter400x267.jpg)
Second same component still intact
(http://galerie.experimentierkasten-board.de/data/media/201/DSA602filterklein1400x242.jpg)
Small filters
Images of parts of the DSA602A:
(http://galerie.experimentierkasten-board.de/data/media/201/DSA602Afiter400x267.jpg)
Second same component still intact
(http://galerie.experimentierkasten-board.de/data/media/201/DSA602Afilterklein400x199.jpg)
Small filters
I am looking forward to your comments
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Not sure what the pictures are showing.. two different boards or boards from DSA602 and DSA602A?
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Hello Johnny10
The pictures are showing views of boards from DSA602 (3) and DSA602A (2).
The pictures 1,2 and 3 of my last post show different views of the first power supply board of the DSA602.
The pictures 4 and 5 of my last post show the analog views of the same power supply board of the DSA602A.
For me it is remarkable that the same capacitors RIFA 0.6 uF X and RIFA 0.6 uF X2, both on the upper left of the boards, and also ONLY these, are fumed in these different oscilloscopes DSA 602 and DSA 602A, randomly?
I must also admit that this incident was my first encounter with this type of interference suppression capacitors.
Regards
Physikfan
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I guess next week I will have to open these two beasts up and do some work.
Phew and they are beasts !
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Check your HP kit as well. It's usually full of the flame throwing bastards!
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For me it is remarkable that the same capacitors RIFA 0.6 uF X and RIFA 0.6 uF X2, both on the upper left of the boards, and also ONLY these, are fumed in these different oscilloscopes DSA 602 and DSA 602A, randomly?
Unfortunately, these RIFA caps are infamous for blowing up. The only random thing about them is which one will burst into flames next. Change them all before applying power again. Those small 0.015 look like RIFAs, too.
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Hi Johnny10
If you will do the job next week
"I guess next week I will have to open these two beasts up and do some work."
please, could you post exactly the capacitors which you will use for the replacement.
You are planning to use new Y2 capacitors (two 0.6uF caps and two 0.015uF caps) for each of your DSA602´s of a certain brand or only high quality capacitors for high voltages around 1000V DC?
By the way, nice lab!
Regards
Physikfan
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I am going to start looking for caps this week.
I went to my local surplus store but no x2 or Y caps in his stock.
Will have to look at suppliers.
So far they don't seem too expensive just that I am going to have to order through mail.
Will keep you informed.
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Hi Johnny10 and all DSA602 and DSA602A owners
Please which DSA602 and DSA602A owner has already had its device open and
can tell me something about the wiring of this board just next to the power supply?
(http://galerie.experimentierkasten-board.de/data/media/201/DSA602Avoltagesupplyboard400x267.jpg)
It is about the two-pole white plug, the third from the left bottom, with the two cables red and brown.
In my DSA602A it is present, in my DSA602 it is missing.
I wonder now, due to a lack of circuit diagram, whether it has to do with the power supply of the floppy disk drive in the DSA602A.
The DSA602A has one, the DSA602 has none.
Best regards
Physikfan
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Hi bd139
Please what do you mean with IPA, iso-propyl-alcohol?
Regards
Physicfan
FYI, one other shorthand ---> DNA = denatured alcohol and not the stuff you provide to Ancestry. :-+
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No pictures of it but,
A customer was having an issue with a temp controller so they changed it out and wanted me to get calibration data on it. So they hand me a 120vac cut cord the controller and a picture of how it was wired. In the picture there was a black/white wire and everything thing else was red wiring.
I didn't even think and wired the 120vac black and white wires to the same wires as in the picture. Well, that was the normally closed relay and once I plugged into the outlet I tripped the breaker. Needless to say, the unit issues were put to rest since the unit was designed for 24 vdc and 120vac fried everything in it to power on.
Morale of the incident is when a customer tries to help, it never seems to end up good.
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OK
So I opened the DSA602A !! Yikes that thing is heavy.
Sent Pic of control rectifier board on DSA602A
How did you get to RIFA chips?
Through back panel?
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Hello Johnny10
To remove the power supply module from the DSA602A
the first step is to unscrew 14 screws at the back of the DSA602.
Before you completely remove this power supply module from the DSA602A, the second step is to disconnect the cables that you have shown in your image.
Your second DSA oscilloscope is also a DSA602A?
Regards
Physikfan
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Second scope is DSA 602 no floppy drive
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Hi Johnny10
Here are links containing access to DSA manuals:
http://w140.com/tekwiki/wiki/DSA600 (http://w140.com/tekwiki/wiki/DSA600)
bee.mif.pg.gda.pl/ciasteczkowypotwor/Tek/DSA600-service.pdf
You have posted this nice picture of the DSA602A.
Please could you post also the analog picture of the DSA602?
Regards
Physikfan
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OK I pulled out power supply.
Posted pics of both DSA units in previous post.... they look identical to me and the date markers are both from 1991.
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Hello Johnny10
Have you finished the replacement of the X2 capacitors?
What kind of capacitors have you used finally?
Regards
Physikfan
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No
I was working on getting the front keys on my datron 4000a working.
From another thread you can see that was all I needed to finish.
Success on that front.
Last 4 days prepping for Hurricane Irma.
I am on the East Coast... made it alright.
Next is DSA602A
Did you also change Y caps?
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Back in the early days of personal computers (S-100 era) I acquired several very expensive 64K dynamic RAM boards since they were defective. Turns out the factory silk screened the component polarity incorrectly for the main tantalum cap on the minus voltage pwr supply. Plus symbol pointed to negative pwr rail and "-" pointed to ground. :palm: They then went and stuffed the boards to match the indicated polarity. After a bit of usage they all when POOF! Magic smoke went out and the boards were sold for scrap. I installed new caps with the + lead to ground and "-" lead to the minus pwr rail and they all worked! 8)
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Just now getting back to the repair desk.
These are the X2 caps I ordered for my units.
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Please how much did you pay for these capacitors and
please could you tell me your source?
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Quite reasonable but probably long wait.
http://www.ebay.com/itm/10pcs-Blue-film-capacitor-305V-47M-0-47UF-pin-pitch-25mm/302247792840?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 (http://www.ebay.com/itm/10pcs-Blue-film-capacitor-305V-47M-0-47UF-pin-pitch-25mm/302247792840?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649)
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Considering the upcoming projects I must be very careful after reading this thread.
Being cautious as I am and having the experience of a few messy explosions in the past, I have been very lucky these last several years.
It is not the BANG or the SMELL that is so bad, it's cleaning up the mess.... :palm:
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if you want very good caps at a cheap price, panasonic are very good.
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if you want very good caps at a cheap price, panasonic are very good.
Indeed, don't know why people want to use the cheap shenzen-market (CQC) parts, especially for replacement of line-filter X & Y caps in quality equipment.
Here in Europe you can buy the Panasonic/Matsushita-parts @ Conrad & Reichelt (or Mouser/Digikey), also you could look for the modern 'red' WIMA-X2 & Y2 caps (Germany made) if you search for the right partnumber chosen from the datasheet > that's just my way of working. ;)
I will attach the datasheets of the parts I use for this application: