Elecraft

Help! Rescue me from stupid error!

Classic

List

Threaded

13 messages Options

Vic Rosenthal

Help! Rescue me from stupid error!

I just did one of the dumbest things I've done since I tried to swim
across the Susquehanna river with all my clothes on. I survived that,
but I need help with something else.

I just turned on a computer plugged into 230v with the switch on the
power supply set to 115v. Result: bang, smoke, house breaker (16a) pops.

I took the power supply apart (it is a funny size so I have little
confidence I could replace it). I found two obviously bad components: 1)
an 8a fuse -- no problem. 2) something marked znr1 on the board, a
component wrapped in heatshrink tubing. It was completely destroyed.
Next to it is a similar part labeled znr2. I haven't removed it yet --
so I am not sure it is good. It might be the same as the first one and
it might be marked under the heatshrink.

There is a bridge rectifier nearby which checks good. All traces look
ok. I am hoping there is someone out there who is familiar with these
supplies who can suggest what these are (zener diodes? What voltage?)
The board is made in such a way that it is difficult to trace the wiring
-- but these parts are right near the power input.

--
Vic, K2VCO/4X6GP
Rehovot, Israel
http://www.qsl.net/k2vco/
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

tomb18

Re: Help! Rescue me from stupid error!

Hi,Typically a device labeled as znr is a MOV, metal oxide varistor used to protect cir u its from excessive voltage or currents. Remove the other one, you will probably find a marking.
73s Tom
va2fsq.com

On 9/9/14, "Vic, K2VCO" <[hidden email]> wrote:

> I just did one of the dumbest things I've done since I tried to swim across the Susquehanna river with all my clothes on. I survived that, but I need help with something else.
>
> I just turned on a computer plugged into 230v with the switch on the power supply set to 115v. Result: bang, smoke, house breaker (16a) pops.
>
> I took the power supply apart (it is a funny size so I have little confidence I could replace it). I found two obviously bad components: 1) an 8a fuse -- no problem. 2) something marked znr1 on the board, a component wrapped in heatshrink tubing. It was completely destroyed. Next to it is a similar part labeled znr2. I haven't removed it yet -- so I am not sure it is good. It might be the same as the first one and it might be marked under the heatshrink.
>
> There is a bridge rectifier nearby which checks good. All traces look ok. I am hoping there is someone out there who is familiar with these supplies who can suggest what these are (zener diodes? What voltage?)
> The board is made in such a way that it is difficult to trace the wiring -- but these parts are right near the power input.
>
> --
> Vic, K2VCO/4X6GP
> Rehovot, Israel
> http://www.qsl.net/k2vco/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] <[hidden email]>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
>

Charlie T, K3ICH

Re: Help! Rescue me from stupid error!

In reply to this post by Vic Rosenthal

A 'ZNR" is a Zinc Oxide non-linear Resistor. It is the mechanical
equivalent of a Zener Diode. It is a bidirectional (AC) device that will
conduct when a certain level of voltage is applied across it. They don't
typically have as sharp a "knee" as a real Zener, but are very effective for
what they do. Basically , a voltage surge or transient protector.
Hopefully, they worked but are probably blown and should be replaced.

As for the rest of the stuff, I'm sure you'll find some more (inexpensive)
things to replace and the system will come back to life.

Good Luck on the repair, Charlie k3ICH

----- Original Message -----
From: "Vic, K2VCO" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Tuesday, September 09, 2014 1:23 PM
Subject: [Elecraft] Help! Rescue me from stupid error!

>I just did one of the dumbest things I've done since I tried to swim across
>the Susquehanna river with all my clothes on. I survived that, but I need
>help with something else.
>
> I just turned on a computer plugged into 230v with the switch on the power
> supply set to 115v. Result: bang, smoke, house breaker (16a) pops.
>
> I took the power supply apart (it is a funny size so I have little
> confidence I could replace it). I found two obviously bad components: 1)
> an 8a fuse -- no problem. 2) something marked znr1 on the board, a
> component wrapped in heatshrink tubing. It was completely destroyed. Next
> to it is a similar part labeled znr2. I haven't removed it yet --
> so I am not sure it is good. It might be the same as the first one and it
> might be marked under the heatshrink.
>
> There is a bridge rectifier nearby which checks good. All traces look ok.
> I am hoping there is someone out there who is familiar with these supplies
> who can suggest what these are (zener diodes? What voltage?)
> The board is made in such a way that it is difficult to trace the
> wiring -- but these parts are right near the power input.
>
> --
> Vic, K2VCO/4X6GP
> Rehovot, Israel
> http://www.qsl.net/k2vco/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Fred Townsend-2

Re: Help! Rescue me from stupid error!

In reply to this post by Vic Rosenthal

Vic:
Sorry you passed the smoke test. Your mystery components sound like transient suppressors. They are not needed for normal operation. They are there to suppress lightning or other power line disturbances. To find out carefully cut out ZNR1&2 and clean up any ashes. Then replace the fuse and try the computer. If you are lucky the computer will run. Don't forget to change back to 120 VAC setting.

Good luck,
Fred, AE6QL

-----Original Message-----

>From: "Vic, K2VCO" <[hidden email]>
>Sent: Sep 9, 2014 10:23 AM
>To: Elecraft Reflector <[hidden email]>
>Subject: [Elecraft] Help! Rescue me from stupid error!
>
>I just did one of the dumbest things I've done since I tried to swim
>across the Susquehanna river with all my clothes on. I survived that,
>but I need help with something else.
>
>I just turned on a computer plugged into 230v with the switch on the
>power supply set to 115v. Result: bang, smoke, house breaker (16a) pops.
>
>I took the power supply apart (it is a funny size so I have little
>confidence I could replace it). I found two obviously bad components: 1)
>an 8a fuse -- no problem. 2) something marked znr1 on the board, a
>component wrapped in heatshrink tubing. It was completely destroyed.
>Next to it is a similar part labeled znr2. I haven't removed it yet --
>so I am not sure it is good. It might be the same as the first one and
>it might be marked under the heatshrink.
>
>There is a bridge rectifier nearby which checks good. All traces look
>ok. I am hoping there is someone out there who is familiar with these
>supplies who can suggest what these are (zener diodes? What voltage?)
>The board is made in such a way that it is difficult to trace the wiring
>-- but these parts are right near the power input.
>
>--
>Vic, K2VCO/4X6GP
>Rehovot, Israel
>http://www.qsl.net/k2vco/
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]

Vic Rosenthal

Re: Help! Rescue me from stupid error!

Vic Rosenthal

Re: Help! Rescue me from stupid error!

In reply to this post by Fred Townsend-2

Took the second one out. It is labeled TVR07241, which is a 240v
varistor! I can get these to replace them.
I think this one is undamaged (at least, it isn't blown up or shorted).
I wonder if the other one was a 115V one which was only in the circuit
when the switch was set for 115. That would certainly explain it blowing
when I plugged it into 230!

On 9/9/14 8:41 PM, Fred Townsend wrote:

>
> Vic: Sorry you passed the smoke test. Your mystery components sound
> like transient suppressors. They are not needed for normal operation.
> They are there to suppress lightning or other power line
> disturbances. To find out carefully cut out ZNR1&2 and clean up any
> ashes. Then replace the fuse and try the computer. If you are lucky
> the computer will run. Don't forget to change back to 120 VAC
> setting.
>
> Good luck, Fred, AE6QL
>
> -----Original Message-----
>> From: "Vic, K2VCO" <[hidden email]> Sent: Sep 9, 2014 10:23
>> AM To: Elecraft Reflector <[hidden email]> Subject:
>> [Elecraft] Help! Rescue me from stupid error!
>>
>> I just did one of the dumbest things I've done since I tried to
>> swim across the Susquehanna river with all my clothes on. I
>> survived that, but I need help with something else.
>>
>> I just turned on a computer plugged into 230v with the switch on
>> the power supply set to 115v. Result: bang, smoke, house breaker
>> (16a) pops.
>>
>> I took the power supply apart (it is a funny size so I have little
>> confidence I could replace it). I found two obviously bad
>> components: 1) an 8a fuse -- no problem. 2) something marked znr1
>> on the board, a component wrapped in heatshrink tubing. It was
>> completely destroyed. Next to it is a similar part labeled znr2. I
>> haven't removed it yet -- so I am not sure it is good. It might be
>> the same as the first one and it might be marked under the
>> heatshrink.
>>
>> There is a bridge rectifier nearby which checks good. All traces
>> look ok. I am hoping there is someone out there who is familiar
>> with these supplies who can suggest what these are (zener diodes?
>> What voltage?) The board is made in such a way that it is difficult
>> to trace the wiring -- but these parts are right near the power
>> input.
>>
>> -- Vic, K2VCO/4X6GP Rehovot, Israel http://www.qsl.net/k2vco/
>> ______________________________________________________________
>> Elecraft mailing list Home:
>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>> http://mailman.qth.net/mmfaq.htm Post:
>> mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email list: http://www.qsl.net/donate.html Message delivered to
>> [hidden email]
>

--
Vic

--
Vic, K2VCO/4X6GP
Rehovot, Israel
http://www.qsl.net/k2vco/
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Fred Townsend-2

Re: Help! Rescue me from stupid error!

In reply to this post by Vic Rosenthal

My guess is they are both 240V rated. The parts are cheap and there are several brands which cross over with similar part numbers. I would replace both. If 240 are not available then 270 will work fine as well. Until parts are obtained you may use the computer. Odds are there will not be any power distrubances in the mean time. Sort of like using the spare tire. Two flats in a row are not likely to happen.

Fred

-----Original Message-----

>From: "Vic, K2VCO" <[hidden email]>
>Sent: Sep 9, 2014 10:59 AM
>To: Fred Townsend <[hidden email]>, Elecraft Reflector <[hidden email]>
>Subject: Re: [Elecraft] Help! Rescue me from stupid error!
>
>Took the second one out. It is labeled TVR07241, which is a 240v
>varistor! I can get these to replace them.
>I think this one is undamaged (at least, it isn't blown up or shorted).
>I wonder if the other one was a 115V one which was only in the circuit
>when the switch was set for 115. That would certainly explain it blowing
>when I plugged it into 230!
>
>On 9/9/14 8:41 PM, Fred Townsend wrote:
>>
>> Vic: Sorry you passed the smoke test. Your mystery components sound
>> like transient suppressors. They are not needed for normal operation.
>> They are there to suppress lightning or other power line
>> disturbances. To find out carefully cut out ZNR1&2 and clean up any
>> ashes. Then replace the fuse and try the computer. If you are lucky
>> the computer will run. Don't forget to change back to 120 VAC
>> setting.
>>
>> Good luck, Fred, AE6QL
>>
>> -----Original Message-----
>>> From: "Vic, K2VCO" <[hidden email]> Sent: Sep 9, 2014 10:23
>>> AM To: Elecraft Reflector <[hidden email]> Subject:
>>> [Elecraft] Help! Rescue me from stupid error!
>>>
>>> I just did one of the dumbest things I've done since I tried to
>>> swim across the Susquehanna river with all my clothes on. I
>>> survived that, but I need help with something else.
>>>
>>> I just turned on a computer plugged into 230v with the switch on
>>> the power supply set to 115v. Result: bang, smoke, house breaker
>>> (16a) pops.
>>>
>>> I took the power supply apart (it is a funny size so I have little
>>> confidence I could replace it). I found two obviously bad
>>> components: 1) an 8a fuse -- no problem. 2) something marked znr1
>>> on the board, a component wrapped in heatshrink tubing. It was
>>> completely destroyed. Next to it is a similar part labeled znr2. I
>>> haven't removed it yet -- so I am not sure it is good. It might be
>>> the same as the first one and it might be marked under the
>>> heatshrink.
>>>
>>> There is a bridge rectifier nearby which checks good. All traces
>>> look ok. I am hoping there is someone out there who is familiar
>>> with these supplies who can suggest what these are (zener diodes?
>>> What voltage?) The board is made in such a way that it is difficult
>>> to trace the wiring -- but these parts are right near the power
>>> input.
>>>
>>> -- Vic, K2VCO/4X6GP Rehovot, Israel http://www.qsl.net/k2vco/
>>> ______________________________________________________________
>>> Elecraft mailing list Home:
>>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>>> http://mailman.qth.net/mmfaq.htm Post:
>>> mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net Please help support this
>>> email list: http://www.qsl.net/donate.html Message delivered to
>>> [hidden email]
>>
>
>--
>Vic
>
>--
>Vic, K2VCO/4X6GP
>Rehovot, Israel
>http://www.qsl.net/k2vco/

Josh Fiden

Re: Help! Rescue me from stupid error!

In reply to this post by Vic Rosenthal

Typical on these type of supplies is the voltage selector switch is
single pole which converts between being a bridge to the filter caps to
a voltage doubler configuration. So, where you should have had about
320VDC, you would be in doubler mode and gotten 640VDC (230V*1.4*2).

Protection devices prior to the bridge should be okay to 240VAC. ZNR1 &
2 are most likely across each of the filter caps which are in series for
the doubler. Hopefully they did their job before killing anything else.
They would be identical.

73,
Josh W6XU

On 9/9/2014 10:59 AM, Vic, K2VCO wrote:

> Took the second one out. It is labeled TVR07241, which is a 240v
> varistor! I can get these to replace them.
> I think this one is undamaged (at least, it isn't blown up or
> shorted). I wonder if the other one was a 115V one which was only in
> the circuit when the switch was set for 115. That would certainly
> explain it blowing when I plugged it into 230!
>
> On 9/9/14 8:41 PM, Fred Townsend wrote:
>>
>> Vic: Sorry you passed the smoke test. Your mystery components sound
>> like transient suppressors. They are not needed for normal operation.
>> They are there to suppress lightning or other power line
>> disturbances. To find out carefully cut out ZNR1&2 and clean up any
>> ashes. Then replace the fuse and try the computer. If you are lucky
>> the computer will run. Don't forget to change back to 120 VAC
>> setting.
>>
>> Good luck, Fred, AE6QL
>>
>> -----Original Message-----
>>> From: "Vic, K2VCO" <[hidden email]> Sent: Sep 9, 2014 10:23
>>> AM To: Elecraft Reflector <[hidden email]> Subject:
>>> [Elecraft] Help! Rescue me from stupid error!
>>>
>>> I just did one of the dumbest things I've done since I tried to
>>> swim across the Susquehanna river with all my clothes on. I
>>> survived that, but I need help with something else.
>>>
>>> I just turned on a computer plugged into 230v with the switch on
>>> the power supply set to 115v. Result: bang, smoke, house breaker
>>> (16a) pops.
>>>
>>> I took the power supply apart (it is a funny size so I have little
>>> confidence I could replace it). I found two obviously bad
>>> components: 1) an 8a fuse -- no problem. 2) something marked znr1
>>> on the board, a component wrapped in heatshrink tubing. It was
>>> completely destroyed. Next to it is a similar part labeled znr2. I
>>> haven't removed it yet -- so I am not sure it is good. It might be
>>> the same as the first one and it might be marked under the
>>> heatshrink.
>>>
>>> There is a bridge rectifier nearby which checks good. All traces
>>> look ok. I am hoping there is someone out there who is familiar
>>> with these supplies who can suggest what these are (zener diodes?
>>> What voltage?) The board is made in such a way that it is difficult
>>> to trace the wiring -- but these parts are right near the power
>>> input.
>>>
>>> -- Vic, K2VCO/4X6GP Rehovot, Israel http://www.qsl.net/k2vco/
>>> ______________________________________________________________
>>> Elecraft mailing list Home:
>>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>>> http://mailman.qth.net/mmfaq.htm Post:
>>> mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net Please help support this
>>> email list: http://www.qsl.net/donate.html Message delivered to
>>> [hidden email]
>>
>

Elecraft mailing list

Re: Help! Rescue me from stupid error!

In reply to this post by Charlie T, K3ICH

There is nothing mechanical about a ZNR. The electrical equivalent is back to back Zener diodes with a capacitor. Some people call them Transzorbs or MOVs to get by trade marks. The ZNR is a Panasonic trade mark

George, W6GF

On Tuesday, September 9, 2014 10:54 AM, "Charlie T, K3ICH" <[hidden email]> wrote:

A 'ZNR" is a Zinc Oxide non-linear Resistor. It is the mechanical
equivalent of a Zener Diode. It is a bidirectional (AC) device that will
conduct when a certain level of voltage is applied across it. They don't
typically have as sharp a "knee" as a real Zener, but are very effective for
what they do. Basically , a voltage surge or transient protector.
Hopefully, they worked but are probably blown and should be replaced.

As for the rest of the stuff, I'm sure you'll find some more (inexpensive)
things to replace and the system will come back to life.

Good Luck on the repair, Charlie k3ICH

----- Original Message -----
From: "Vic, K2VCO" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Tuesday, September 09, 2014 1:23 PM
Subject: [Elecraft] Help! Rescue me from stupid error!

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Fred Townsend-2

Re: Help! Rescue me from stupid error!

In reply to this post by Vic Rosenthal

George: Not to put too fine a point on it but ZNRs are large and slow moving so they do have mechanical aspects but more to the point they do NOT have capacitance, save lead capacitance (a few pf), and do NOT act like zeners. They are much slower (ms vrs ns). They are NOT transorbs which are zener like and have junctions, hole electron pairs, transition capacitance, etc. Without hole-electron pairs and their ns speed, Charlie's definition of non-linear resistors is much more accurate.

73, Fred, AE6QL

-----Original Message-----

>From: george fritkin via Elecraft <[hidden email]>
>Sent: Sep 9, 2014 12:38 PM
>To: "Charlie T, K3ICH" <[hidden email]>, "[hidden email]" <[hidden email]>
>Subject: Re: [Elecraft] Help! Rescue me from stupid error!
>
>There is nothing mechanical about a ZNR. The electrical equivalent is back to back Zener diodes with a capacitor. Some people call them Transzorbs or MOVs to get by trade marks. The ZNR is a Panasonic trade mark
>
>George, W6GF
>
>
>On Tuesday, September 9, 2014 10:54 AM, "Charlie T, K3ICH" <[hidden email]> wrote:
>
>
>
>A 'ZNR" is a Zinc Oxide non-linear Resistor. It is the mechanical
>equivalent of a Zener Diode. It is a bidirectional (AC) device that will
>conduct when a certain level of voltage is applied across it. They don't
>typically have as sharp a "knee" as a real Zener, but are very effective for
>what they do. Basically , a voltage surge or transient protector.
>Hopefully, they worked but are probably blown and should be replaced.
>
>As for the rest of the stuff, I'm sure you'll find some more (inexpensive)
>things to replace and the system will come back to life.
>
>Good Luck on the repair, Charlie k3ICH
>
>
>----- Original Message -----
>From: "Vic, K2VCO" <[hidden email]>
>To: "Elecraft Reflector" <[hidden email]>
>Sent: Tuesday, September 09, 2014 1:23 PM
>Subject: [Elecraft] Help! Rescue me from stupid error!
>
>
>>I just did one of the dumbest things I've done since I tried to swim across
>>the Susquehanna river with all my clothes on. I survived that, but I need
>>help with something else.
>>
>> I just turned on a computer plugged into 230v with the switch on the power
>> supply set to 115v. Result: bang, smoke, house breaker (16a) pops.
>>
>> I took the power supply apart (it is a funny size so I have little
>> confidence I could replace it). I found two obviously bad components: 1)
>> an 8a fuse -- no problem. 2) something marked znr1 on the board, a
>> component wrapped in heatshrink tubing. It was completely destroyed. Next
>> to it is a similar part labeled znr2. I haven't removed it yet --
>> so I am not sure it is good. It might be the same as the first one and it
>> might be marked under the heatshrink.
>>
>> There is a bridge rectifier nearby which checks good. All traces look ok.
>> I am hoping there is someone out there who is familiar with these supplies
>> who can suggest what these are (zener diodes? What voltage?)
>> The board is made in such a way that it is difficult to trace the
>> wiring -- but these parts are right near the power input.
>>
>> --
>> Vic, K2VCO/4X6GP
>> Rehovot, Israel
>> http://www.qsl.net/k2vco/
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]

Charlie T, K3ICH

Re: Help! Rescue me from stupid error!

In reply to this post by Elecraft mailing list

Maybe "mechanical" was not the proper choice of words. What I was implying was that it is not a junction device as would be a Zener or an SCR. It is simply a chunk of Zinc Oxide that with the proper mix will start to conduct at a predictable voltage.

In that sense, it is more mechanical than a Zener.

Chas
----- Original Message -----
From: george fritkin
To: Charlie T, K3ICH ; [hidden email]
Sent: Tuesday, September 09, 2014 3:38 PM
Subject: Re: [Elecraft] Help! Rescue me from stupid error!

There is nothing mechanical about a ZNR. The electrical equivalent is back to back Zener diodes with a capacitor. Some people call them Transzorbs or MOVs to get by trade marks. The ZNR is a Panasonic trade mark

George, W6GF

On Tuesday, September 9, 2014 10:54 AM, "Charlie T, K3ICH" <[hidden email]> wrote:

A 'ZNR" is a Zinc Oxide non-linear Resistor. It is the mechanical
equivalent of a Zener Diode. It is a bidirectional (AC) device that will
conduct when a certain level of voltage is applied across it. They don't
typically have as sharp a "knee" as a real Zener, but are very effective for
what they do. Basically , a voltage surge or transient protector.
Hopefully, they worked but are probably blown and should be replaced.

As for the rest of the stuff, I'm sure you'll find some more (inexpensive)
things to replace and the system will come back to life.

Good Luck on the repair, Charlie k3ICH

----- Original Message -----
From: "Vic, K2VCO" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Tuesday, September 09, 2014 1:23 PM
Subject: [Elecraft] Help! Rescue me from stupid error!

>I just did one of the dumbest things I've done since I tried to swim across
>the Susquehanna river with all my clothes on. I survived that, but I need
>help with something else.
>
> I just turned on a computer plugged into 230v with the switch on the power
> supply set to 115v. Result: bang, smoke, house breaker (16a) pops.
>
> I took the power supply apart (it is a funny size so I have little
> confidence I could replace it). I found two obviously bad components: 1)
> an 8a fuse -- no problem. 2) something marked znr1 on the board, a
> component wrapped in heatshrink tubing. It was completely destroyed. Next
> to it is a similar part labeled znr2. I haven't removed it yet --
> so I am not sure it is good. It might be the same as the first one and it
> might be marked under the heatshrink.
>
> There is a bridge rectifier nearby which checks good. All traces look ok.
> I am hoping there is someone out there who is familiar with these supplies
> who can suggest what these are (zener diodes? What voltage?)
> The board is made in such a way that it is difficult to trace the
> wiring -- but these parts are right near the power input.
>
> --
> Vic, K2VCO/4X6GP
> Rehovot, Israel
> http://www.qsl.net/k2vco/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Vic Rosenthal

Re: Help! Rescue me from stupid error!

In reply to this post by Elecraft mailing list

Thank to everyone who responded to my cry for help after I damaged my
computer PS. I replaced the MOVs and the fuse and it works!
I do not recommend running 120v equipment on 240v in general!

On 9/9/2014 12:38 PM, george fritkin via Elecraft wrote:

> There is nothing mechanical about a ZNR. The electrical equivalent is back to back Zener diodes with a capacitor. Some people call them Transzorbs or MOVs to get by trade marks. The ZNR is a Panasonic trade mark
>
> George, W6GF
>
>
> On Tuesday, September 9, 2014 10:54 AM, "Charlie T, K3ICH" <[hidden email]> wrote:
>
>
>
> A 'ZNR" is a Zinc Oxide non-linear Resistor. It is the mechanical
> equivalent of a Zener Diode. It is a bidirectional (AC) device that will
> conduct when a certain level of voltage is applied across it. They don't
> typically have as sharp a "knee" as a real Zener, but are very effective for
> what they do. Basically , a voltage surge or transient protector.
> Hopefully, they worked but are probably blown and should be replaced.
>
> As for the rest of the stuff, I'm sure you'll find some more (inexpensive)
> things to replace and the system will come back to life.
>
> Good Luck on the repair, Charlie k3ICH
>
>
> ----- Original Message -----
> From: "Vic, K2VCO" <[hidden email]>
> To: "Elecraft Reflector" <[hidden email]>
> Sent: Tuesday, September 09, 2014 1:23 PM
> Subject: [Elecraft] Help! Rescue me from stupid error!
>
>
>> I just did one of the dumbest things I've done since I tried to swim across
>> the Susquehanna river with all my clothes on. I survived that, but I need
>> help with something else.
>>
>> I just turned on a computer plugged into 230v with the switch on the power
>> supply set to 115v. Result: bang, smoke, house breaker (16a) pops.
>>
>> I took the power supply apart (it is a funny size so I have little
>> confidence I could replace it). I found two obviously bad components: 1)
>> an 8a fuse -- no problem. 2) something marked znr1 on the board, a
>> component wrapped in heatshrink tubing. It was completely destroyed. Next
>> to it is a similar part labeled znr2. I haven't removed it yet --
>> so I am not sure it is good. It might be the same as the first one and it
>> might be marked under the heatshrink.
>>
>> There is a bridge rectifier nearby which checks good. All traces look ok.
>> I am hoping there is someone out there who is familiar with these supplies
>> who can suggest what these are (zener diodes? What voltage?)
>> The board is made in such a way that it is difficult to trace the
>> wiring -- but these parts are right near the power input.

--
73,
Vic, K2VCO/4X6GP
Rehovot, Israel
http://www.qsl.net/k2vco/
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

gm3sek

Re: Help! Rescue me from stupid error!

In reply to this post by Fred Townsend-2

>
>George: Not to put too fine a point on it but ZNRs are large and slow
moving
>so they do have mechanical aspects but more to the point they do NOT
have
>capacitance, save lead capacitance (a few pf),

Not true: MOVs have a self-capacitance on the order of 1000pF, which is
sometimes an advantage. The surge limiting components with a very low
capacitance are spark gaps, but those have quite different
characteristics.

MOVs are bidirectional devices which are "soft limiting", so they are
not as effective as transzorbs in limiting any incoming voltage spikes.
On the other hand, MOVs are bulk-effect devices which are capable of
absorbing much more surge energy than the semiconductor junctions in the
transzorbs.

The main function of MOVs is to "take a bullet" for the more sensitive
(and valuable) components downstream. However, this also involves some
cumulative damage to the crystal structure and eventually an MOV will
either become ineffective or fail (failure could involve either an
upward or a downward shift in the limiting voltage, ending in either an
open or a short circuit). These failure modes can be an acceptable price
to pay for the energy absorbing capabilities, so long as both the
designer and the user are aware of the possibilities.

The most effective protection strategies will combine two or more
different types of device to exploit each of their best features. One
example is to install a big MOV first in line, followed by a series
impedance (usually a mains filter) and then a fast device such as a
transzorb to clip any residual spikes.

Another very simple tip is to install all of these supply protection
components AFTER the switch, so they are not exposed to surges when
equipment is not in use.

73 from Ian GM3SEK

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]