Board burns
- Thread starter nsaspook
- Start date
That's more like a victim resistor...
Not really a burn this time.
Had to repair a board that used the successor of the Z80 CPU, the Z180. Nothing wrong with the CPU, some I/O isolation SSR chips were cooked from voltage surges from a motor controller. A VIP board in a classic production tool. What ever it takes to keep the chips rolling out the door.
Had to repair a board that used the successor of the Z80 CPU, the Z180. Nothing wrong with the CPU, some I/O isolation SSR chips were cooked from voltage surges from a motor controller. A VIP board in a classic production tool. What ever it takes to keep the chips rolling out the door.
I did have a little bit of trouble with my solar power panel isolation switches. Over a number of years, 2 ended up like this and one other failed but not so spectacularly.
I got up on the roof and knocked the burning mass apart with a stick then wrapped the wires in plastic and tape. Not something fun to do with each string a 2.5KW 400VDC supply!
All 4 have now been professionally replaced with new ones in metal enclosures at quite a bit of expense, more that I was bargaining on to tell the truth.
This is getting stupid. Smoked another one. We have a problem at pretty low power levels (~1000W beam power) and energy. It doesn't look like normally vacuum electrical arc burns, It looks like RF burns but it should be a DC plasma. I'm glad this thing is very well shielded with lead.
That melted metal slit is https://www.azom.com/article.aspx?ArticleID=9108
That melted metal slit is https://www.azom.com/article.aspx?ArticleID=9108
Someone was checking resistance on a high power high voltage circuit and forgot to remove the meter before energizing the power.
Board looks clean but I would suspect the OHM function calibration.
Terminal arcing.
It arc'd from the battery terminal to the equipment ground through the case. Max potential 90KV @100mA.
No idea if it still works but it's headed to Fluke for a possible repair or replacement.
Excellent containment of arc damage and fire suppression. This is why companies buy expensive Fluke meters.
Board looks clean but I would suspect the OHM function calibration.
Terminal arcing.
It arc'd from the battery terminal to the equipment ground through the case. Max potential 90KV @100mA.
No idea if it still works but it's headed to Fluke for a possible repair or replacement.
Excellent containment of arc damage and fire suppression. This is why companies buy expensive Fluke meters.
People buy flukes because they tend to be repeatable and consistent.
A test or trouble shooting procedure written 25 years ago for some legacy equipment is a real pain in the arse if you can't get a fluke 77 anymore to do the tests.
Companies pay for a fluke because they are slow to change on the surface so the old test procedures remain the same and inside the electronics package from one to another is very reliable as the units age.
Also they don't blow up in your face, but....
A good friend of mine was doing some live tests on a GE silpac drive.
It was a real monster running a 7000 hp motor at 700 vdc.
My chum made the mistake of no looking at the meter and seeing it was on the 10amp un fused plug ( reasons never explained ).
He touched something live on the valve stack and the arc flash happened.
His face and hands were pretty badly burned.
We had some arc flash boundary of approach calculations done.
We went from working on it live to not being allowed near it when it was running unless you had a 40 cal bomb suit on or were more than 20 feet from it.
So its not just the meter its what you are working around.
I do like you board repairs.
Do you mean a Fluke or a fluke look-alike? I've never seen an unfused 10A input on a fluke. Please let us know which model fluke he was using.
I'm pretty sure that any fluke that does have a 10A input has a fuse. A relatively expensive fuse on my Fluke 85 and 87 - like $12 each.
Sure, arc flash originates at the meter probes. No meter can stop that from happening. Repeatable and consistent over long periods of time is right on the money but meter safety is a large consideration to limit meter originated dange when screwups happen.
We only used the Fluke 77 at the time.
You guys say its fused and I am inclined to agree, I have a 77 I use and I am pretty sure there is a fuse in it.
BUT I never use the amp functions, I have proper clamp on meters for that.
Sometime back I dusted off my AVO for some tests.
We no long have and instrument shop so the calibration is off.
We had a few procedures written for the AVO that were never updated, that equipment is gone now but I still like that meter.
Its the only contact test device I have that could do 2200 v ( these days procedures do not allow for contact testing about 1000 volts )
Fused or not fused fluke.
I am probably wrong on my first comment and take that back.
Its not going to do you much good however.
Even with a fuse once you Initiate an arc at these level they can sustain.
Its a runaway reaction as the stuff lights up.
Ive seen it, I've been in the heart of the fireball myself ( lost some hearing for one thing )
I don't know what most of you do.
I work at Utility levels mostly nothing above 13.8 nothing less than 600 ( few exception for some 69 kv remote switching )
I've gone from working in navy surplus boiler suits ( I bought them because of the self extinguishable property of the material ) to modern 12 cal work clothing.
I've gone from contact testing to capacitive sensing test devices
bare hands to bomb suits
ball pen hammers and rubber gloves to hot sticks and bomb suits....
Things have changed a lot.
Two things I notice accidents happen when your green and don;t know any better, and when your old and done this so often your complacent
Onetime I was in a big MG room with my foreman.
Some guys were racking in 4160 starter when something went wrong.
I saw the glow first as the arc started in slow motion.
I had enough time to see my 60 year old foreman running in the air ( cartoon like feet not actually getting traction as he hovered ).
The MG room cleared fast with guys heading for the exist as the smoke filled it.
Two guy racking in the starter were OK because fo the bomb suits ( not required at the time but that was rather proactive company ).
But just 6 month before I was in another place with another employer, working without any PPE and throwing a chain across room at the bottom of some S&C fuese holders because we didn't like to get too close and didn't trust our prints, our test equipment or.... our employer to be honest.
My thoughts for the day.
Watch what you touch and stay as far away from what ever you have to work on if its got any significant voltage or let through energy available.
Ear plugs are your friend....
Deep breath and hold it before switching in case you suck in some fire ball...
Flash protection so you don't get any burns.
Just avoid live stuff if you can....
6900v, 4 feet of clearance
and mounted 5 feet from the floor.
its a hot stick job in a place where you can't use a hot stick.
How did they think I was doing it?
And yes someone is going to aske where are the stress cones then?
Just one more suprise
You guys say its fused and I am inclined to agree, I have a 77 I use and I am pretty sure there is a fuse in it.
BUT I never use the amp functions, I have proper clamp on meters for that.
Sometime back I dusted off my AVO for some tests.
We no long have and instrument shop so the calibration is off.
We had a few procedures written for the AVO that were never updated, that equipment is gone now but I still like that meter.
Its the only contact test device I have that could do 2200 v ( these days procedures do not allow for contact testing about 1000 volts )
Fused or not fused fluke.
I am probably wrong on my first comment and take that back.
Its not going to do you much good however.
Even with a fuse once you Initiate an arc at these level they can sustain.
Its a runaway reaction as the stuff lights up.
Ive seen it, I've been in the heart of the fireball myself ( lost some hearing for one thing )
I don't know what most of you do.
I work at Utility levels mostly nothing above 13.8 nothing less than 600 ( few exception for some 69 kv remote switching )
I've gone from working in navy surplus boiler suits ( I bought them because of the self extinguishable property of the material ) to modern 12 cal work clothing.
I've gone from contact testing to capacitive sensing test devices
bare hands to bomb suits
ball pen hammers and rubber gloves to hot sticks and bomb suits....
Things have changed a lot.
Two things I notice accidents happen when your green and don;t know any better, and when your old and done this so often your complacent
Onetime I was in a big MG room with my foreman.
Some guys were racking in 4160 starter when something went wrong.
I saw the glow first as the arc started in slow motion.
I had enough time to see my 60 year old foreman running in the air ( cartoon like feet not actually getting traction as he hovered ).
The MG room cleared fast with guys heading for the exist as the smoke filled it.
Two guy racking in the starter were OK because fo the bomb suits ( not required at the time but that was rather proactive company ).
But just 6 month before I was in another place with another employer, working without any PPE and throwing a chain across room at the bottom of some S&C fuese holders because we didn't like to get too close and didn't trust our prints, our test equipment or.... our employer to be honest.
My thoughts for the day.
Watch what you touch and stay as far away from what ever you have to work on if its got any significant voltage or let through energy available.
Ear plugs are your friend....
Deep breath and hold it before switching in case you suck in some fire ball...
Flash protection so you don't get any burns.
Just avoid live stuff if you can....
6900v, 4 feet of clearance
and mounted 5 feet from the floor.
its a hot stick job in a place where you can't use a hot stick.
How did they think I was doing it?
And yes someone is going to aske where are the stress cones then?
Just one more suprise
Kjeldgaard
- Joined Apr 7, 2016
- 476
My Fluke 115 is also marked 10A / FUSED
Since this instrument only has the 10 Amp full scale current measurement range, there appears to be no fuse on the other Red Socket.
Since this instrument only has the 10 Amp full scale current measurement range, there appears to be no fuse on the other Red Socket.
The other input is high impedence (10M Ohms) for voltage so there is no need for a fuse at rated voltage levels. Other higher-end meters have fourth terminal for milliAmp/microamp inputs and a 400mA to 600mA fuse. There are, essentially no infused inputs on the 115 meter.
Water damage on a machine.
I/O controller board.
VCC pin7 , Gnd Pin 10, VCC pin 13, magic smoke escaped.
Arc burns on the chip leads.
Some cleaning to see how bad.
That stuff works wonders.
Fixable but already have a replacement assy, thank goodness.
https://www.nxp.com/docs/en/reference-manual/MC68LC302UM.pdf
I/O controller board.
VCC pin7 , Gnd Pin 10, VCC pin 13, magic smoke escaped.
Arc burns on the chip leads.
Some cleaning to see how bad.
That stuff works wonders.
Fixable but already have a replacement assy, thank goodness.
https://www.nxp.com/docs/en/reference-manual/MC68LC302UM.pdf
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