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Abusing brick on the rope

Started by George Herold October 2, 2018
Hi all, I just got done fixing a piece of apparatus that was returned to us.  The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened.  Perhaps what I found weirdest is a power monitor 
LED.  This sits across the +/-15 V rails, with a 12V zener and 5 k ohm 
resistor in series.  (the zener stops it from turning on if one of the rails 
fails.)  It just barley put out any light.... trashed.  
It can take 30 mA forward so >~150 V for too much current.  
And in reverse it doesn't break down till -80 V. 
(I just tested it... it shows a photo response too, 
but don't distract me.) 

So I was in contact with the school that was using this.. checking return 
address, and I asked if they wanted a new brick on the rope.  (Because they 
hadn't returned theirs with the unit.)  It was just then that I learned that 
the brick on the rope had failed!!  And they had purchased a new one from the 
vendor (astrodyne)  

So my current theory is that the brick on the rope failed (somehow) 
and blew 120 Vac through my circuit.. with devastating results.  
Any idea how I can test this theory.. how do I blow up a brick on a 
rope?  (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A.  

Thanks
George H. 
(maybe I should contact astrodyne.)       
On Tuesday, 2 October 2018 20:56:03 UTC+1, George Herold  wrote:
> Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor > LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm > resistor in series. (the zener stops it from turning on if one of the rails > fails.) It just barley put out any light.... trashed. > It can take 30 mA forward so >~150 V for too much current. > And in reverse it doesn't break down till -80 V. > (I just tested it... it shows a photo response too, > but don't distract me.) > > So I was in contact with the school that was using this.. checking return > address, and I asked if they wanted a new brick on the rope. (Because they > hadn't returned theirs with the unit.) It was just then that I learned that > the brick on the rope had failed!! And they had purchased a new one from the > vendor (astrodyne) > > So my current theory is that the brick on the rope failed (somehow) > and blew 120 Vac through my circuit.. with devastating results. > Any idea how I can test this theory.. how do I blow up a brick on a > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > Thanks > George H. > (maybe I should contact astrodyne.)
why would you want to blow it up when you can bypass it? NT
On 02/10/2018 20:55, George Herold wrote:
> Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor > LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm > resistor in series. (the zener stops it from turning on if one of the rails > fails.) It just barley put out any light.... trashed. > It can take 30 mA forward so >~150 V for too much current. > And in reverse it doesn't break down till -80 V. > (I just tested it... it shows a photo response too, > but don't distract me.) > > So I was in contact with the school that was using this.. checking return > address, and I asked if they wanted a new brick on the rope. (Because they > hadn't returned theirs with the unit.) It was just then that I learned that > the brick on the rope had failed!! And they had purchased a new one from the > vendor (astrodyne) > > So my current theory is that the brick on the rope failed (somehow) > and blew 120 Vac through my circuit.. with devastating results. > Any idea how I can test this theory.. how do I blow up a brick on a > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > Thanks > George H. > (maybe I should contact astrodyne.) >
I have seen a LED become dim after being exposed to episodes of reverse polarity. In the case I saw it was spikes of 18-30V (so well above the 5V usually seen for Vr on LED datasheets). The first few zaps seemed to have no effect but damage must have built up. If that is a SMPS then 120V 60Hz appearing on the output seems unlikely but if an output rectifier shorts then spikes of reverse HV at the switching frequency could explain what you saw? piglet
On Tuesday, October 2, 2018 at 4:12:49 PM UTC-4, tabb...@gmail.com wrote:
> On Tuesday, 2 October 2018 20:56:03 UTC+1, George Herold wrote: > > Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor > > LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm > > resistor in series. (the zener stops it from turning on if one of the rails > > fails.) It just barley put out any light.... trashed. > > It can take 30 mA forward so >~150 V for too much current. > > And in reverse it doesn't break down till -80 V. > > (I just tested it... it shows a photo response too, > > but don't distract me.) > > > > So I was in contact with the school that was using this.. checking return > > address, and I asked if they wanted a new brick on the rope. (Because they > > hadn't returned theirs with the unit.) It was just then that I learned that > > the brick on the rope had failed!! And they had purchased a new one from the > > vendor (astrodyne) > > > > So my current theory is that the brick on the rope failed (somehow) > > and blew 120 Vac through my circuit.. with devastating results. > > Any idea how I can test this theory.. how do I blow up a brick on a > > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > > > Thanks > > George H. > > (maybe I should contact astrodyne.) > > why would you want to blow it up when you can bypass it? > > > NT
Bypass how? I've got ~100 of these out in the field (class rooms) if there is a way to fry the power supply that then fried the electronics I'd like to know. George H.
On Tuesday, October 2, 2018 at 4:26:11 PM UTC-4, piglet wrote:
> On 02/10/2018 20:55, George Herold wrote: > > Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor > > LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm > > resistor in series. (the zener stops it from turning on if one of the rails > > fails.) It just barley put out any light.... trashed. > > It can take 30 mA forward so >~150 V for too much current. > > And in reverse it doesn't break down till -80 V. > > (I just tested it... it shows a photo response too, > > but don't distract me.) > > > > So I was in contact with the school that was using this.. checking return > > address, and I asked if they wanted a new brick on the rope. (Because they > > hadn't returned theirs with the unit.) It was just then that I learned that > > the brick on the rope had failed!! And they had purchased a new one from the > > vendor (astrodyne) > > > > So my current theory is that the brick on the rope failed (somehow) > > and blew 120 Vac through my circuit.. with devastating results. > > Any idea how I can test this theory.. how do I blow up a brick on a > > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > > > Thanks > > George H. > > (maybe I should contact astrodyne.) > > > > I have seen a LED become dim after being exposed to episodes of reverse > polarity. In the case I saw it was spikes of 18-30V (so well above the > 5V usually seen for Vr on LED datasheets). The first few zaps seemed to > have no effect but damage must have built up. > > If that is a SMPS then 120V 60Hz appearing on the output seems unlikely > but if an output rectifier shorts then spikes of reverse HV at the > switching frequency could explain what you saw? > > piglet
Right, last night I was thinking just a reverse voltage would do it. (I was picturing some burly student cramming in the power plug the wrong way.) So I tested the LED here... it takes 80 V of Vrev. (And then seems to turn into another dang spad.) It's happy sitting at -40V for several hours Spikes at the switching frequency would explain some of the damage, but there is one section that has an LC filter on the power lines and that should have taken care of the ~100 kHz switching freq. There is the same LED as indicator on that section of circuit. (Oh... checks schematic) The led is before filter.. So your theory stands. I wish I'd heard about the failed SMPS before today... I'll ask more questions... maybe they still have the failed unit and I could do an autopsy. George H.
On 2018/10/02 12:55 PM, George Herold wrote:
> Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor > LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm > resistor in series. (the zener stops it from turning on if one of the rails > fails.) It just barley put out any light.... trashed. > It can take 30 mA forward so >~150 V for too much current. > And in reverse it doesn't break down till -80 V. > (I just tested it... it shows a photo response too, > but don't distract me.) > > So I was in contact with the school that was using this.. checking return > address, and I asked if they wanted a new brick on the rope. (Because they > hadn't returned theirs with the unit.) It was just then that I learned that > the brick on the rope had failed!! And they had purchased a new one from the > vendor (astrodyne) > > So my current theory is that the brick on the rope failed (somehow) > and blew 120 Vac through my circuit.. with devastating results. > Any idea how I can test this theory.. how do I blow up a brick on a > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > Thanks > George H. > (maybe I should contact astrodyne.) >
Power line lightning strike? Was any other equipment in the school damaged or destroyed at the same time? Astrodyne claims 3KV isolation between line and output... John :-#(#
tirsdag den 2. oktober 2018 kl. 21.56.03 UTC+2 skrev George Herold:
> Hi all, I just got done fixing a piece of apparatus that was returned to us. The thing was trashed, (all sorts of blown components) and I've been trying to figure out what happened. Perhaps what I found weirdest is a power monitor > LED. This sits across the +/-15 V rails, with a 12V zener and 5 k ohm > resistor in series. (the zener stops it from turning on if one of the rails > fails.) It just barley put out any light.... trashed. > It can take 30 mA forward so >~150 V for too much current. > And in reverse it doesn't break down till -80 V. > (I just tested it... it shows a photo response too, > but don't distract me.) > > So I was in contact with the school that was using this.. checking return > address, and I asked if they wanted a new brick on the rope. (Because they > hadn't returned theirs with the unit.) It was just then that I learned that > the brick on the rope had failed!! And they had purchased a new one from the > vendor (astrodyne) > > So my current theory is that the brick on the rope failed (somehow) > and blew 120 Vac through my circuit.. with devastating results. > Any idea how I can test this theory.. how do I blow up a brick on a > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. >
no GFCI? else I think you need two short to happen at the same time to get full mains on the output which I don't think is very likely
On Tuesday, 2 October 2018 21:35:31 UTC+1, George Herold  wrote:
> On Tuesday, October 2, 2018 at 4:12:49 PM UTC-4, tabby wrote: > > On Tuesday, 2 October 2018 20:56:03 UTC+1, George Herold wrote:
> > > So my current theory is that the brick on the rope failed (somehow) > > > and blew 120 Vac through my circuit.. with devastating results. > > > Any idea how I can test this theory.. how do I blow up a brick on a > > > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > > > > > Thanks > > > George H. > > > (maybe I should contact astrodyne.) > > > > why would you want to blow it up when you can bypass it? > > > > > > NT > > Bypass how? I've got ~100 of these out in the field (class rooms) if > there is a way to fry the power supply that then fried the electronics > I'd like to know. > > George H.
There must be some miscommunication, as asking how to put 120v into a low voltage connector seems like a crazy question. NT
On Tuesday, October 2, 2018 at 7:13:16 PM UTC-4, tabb...@gmail.com wrote:
> On Tuesday, 2 October 2018 21:35:31 UTC+1, George Herold wrote: > > On Tuesday, October 2, 2018 at 4:12:49 PM UTC-4, tabby wrote: > > > On Tuesday, 2 October 2018 20:56:03 UTC+1, George Herold wrote: > > > > > So my current theory is that the brick on the rope failed (somehow) > > > > and blew 120 Vac through my circuit.. with devastating results. > > > > Any idea how I can test this theory.. how do I blow up a brick on a > > > > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > > > > > > > Thanks > > > > George H. > > > > (maybe I should contact astrodyne.) > > > > > > why would you want to blow it up when you can bypass it? > > > > > > > > > NT > > > > Bypass how? I've got ~100 of these out in the field (class rooms) if > > there is a way to fry the power supply that then fried the electronics > > I'd like to know. > > > > George H. > > There must be some miscommunication, as asking how to put 120v into a low voltage connector seems like a crazy question. > > > NT
Right sorry, I'm guessing some type of HV (>50V) out of the SMPS. I'm not sure what. So my first idea was to pound on the supply, somehow? just a dead short? There are no 'big' inductors in this apparatus, loads are mostly resistive. The good news is all of the circuits had cap multipliers on the PS inputs, and mostly, whatever it was, just blew the unprotected input filter transistors.... next board spin I can add screw terminal blocks and call them input filter/ fuses. :^) to-93 pacs 2N4401/3. The same apparatus is already using ~$2 opamps as amp/ fuses. George H.
On Tuesday, October 2, 2018 at 8:04:26 PM UTC-4, George Herold wrote:
> On Tuesday, October 2, 2018 at 7:13:16 PM UTC-4, tabb...@gmail.com wrote: > > On Tuesday, 2 October 2018 21:35:31 UTC+1, George Herold wrote: > > > On Tuesday, October 2, 2018 at 4:12:49 PM UTC-4, tabby wrote: > > > > On Tuesday, 2 October 2018 20:56:03 UTC+1, George Herold wrote: > > > > > > > So my current theory is that the brick on the rope failed (somehow) > > > > > and blew 120 Vac through my circuit.. with devastating results. > > > > > Any idea how I can test this theory.. how do I blow up a brick on a > > > > > rope? (Astrodyne Mod num. SPU45-210) +15 V @ +2A / -15V @ -1A. > > > > > > > > > > Thanks > > > > > George H. > > > > > (maybe I should contact astrodyne.) > > > > > > > > why would you want to blow it up when you can bypass it? > > > > > > > > > > > > NT > > > > > > Bypass how? I've got ~100 of these out in the field (class rooms) if > > > there is a way to fry the power supply that then fried the electronics > > > I'd like to know. > > > > > > George H. > > > > There must be some miscommunication, as asking how to put 120v into a low voltage connector seems like a crazy question. > > > > > > NT > > Right sorry, I'm guessing some type of HV (>50V) out of the > SMPS. I'm not sure what. So my first idea was to pound on the > supply, somehow? just a dead short? There are no 'big' inductors > in this apparatus, loads are mostly resistive. > The good news is all of the circuits had cap multipliers on the > PS inputs, and mostly, whatever it was, just blew the unprotected > input filter transistors.... next board spin I can add screw > terminal blocks and call them input filter/ fuses. :^) > to-93 pacs > 2N4401/3. > > The same apparatus is already using ~$2 opamps as amp/ fuses. > > George H.
Oh, and I need to add a bit of resistance in the power supply leads, where it was missing before. Should every low power, supply lead have 10 ohms in series? (low power, less than 100 mW) George H.