Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old November 23rd 20, 09:50 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

Well, I have one additional so called "30 amp" Chinese dimmer remaining
after the prior one smoked. This one had a circuit breaker and it did
go today, but not before it started smoking. As I said, I have a good
Astron power supply on the way to replace, but I still had the dimmer in
place until then and outdoors.

This time, I decided to open it up and see what's going on. As others
have said, the Chinese tend to exaggerate ratings so "30 amp" was
probably far from it, but I was surprised what I saw internally:

two HY1707 Mosfets
an LM358
a 78L05
a 555 timer

At 12V, 7 amp load, it seems like it should have been able to handle the
load, but I am wondering that since I was driving it with a switching
supply, maybe that somehow affected the dimmer? By the way, the burnout
was one of the HY1707's. Perhaps they actually need a heatsink instead
of just being attached to the circuit board?

That's absolutely all for the Chinese stuff. I had a constant voltage/
current module on the way, but not even going to open it. Can't trust
it anymore.




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Old November 23rd 20, 10:09 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

On Monday, November 23, 2020 at 3:50:47 PM UTC-5, Chuck wrote:
Well, I have one additional so called "30 amp" Chinese dimmer remaining
after the prior one smoked. This one had a circuit breaker and it did
go today, but not before it started smoking. As I said, I have a good
Astron power supply on the way to replace, but I still had the dimmer in
place until then and outdoors.

This time, I decided to open it up and see what's going on. As others
have said, the Chinese tend to exaggerate ratings so "30 amp" was
probably far from it, but I was surprised what I saw internally:

two HY1707 Mosfets
an LM358
a 78L05
a 555 timer

At 12V, 7 amp load, it seems like it should have been able to handle the
load, but I am wondering that since I was driving it with a switching
supply, maybe that somehow affected the dimmer? By the way, the burnout
was one of the HY1707's. Perhaps they actually need a heatsink instead
of just being attached to the circuit board?

That's absolutely all for the Chinese stuff. I had a constant voltage/
current module on the way, but not even going to open it. Can't trust
it anymore.


A device like that needs a proper heatsink. Even if the metal tab is soldered to the PC it's still inadequate for high power applications.

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Old November 23rd 20, 10:13 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

On 11/23/20 4:09 PM, wrote:
On Monday, November 23, 2020 at 3:50:47 PM UTC-5, Chuck wrote:
Well, I have one additional so called "30 amp" Chinese dimmer remaining
after the prior one smoked. This one had a circuit breaker and it did
go today, but not before it started smoking. As I said, I have a good
Astron power supply on the way to replace, but I still had the dimmer in
place until then and outdoors.

This time, I decided to open it up and see what's going on. As others
have said, the Chinese tend to exaggerate ratings so "30 amp" was
probably far from it, but I was surprised what I saw internally:

two HY1707 Mosfets
an LM358
a 78L05
a 555 timer

At 12V, 7 amp load, it seems like it should have been able to handle the
load, but I am wondering that since I was driving it with a switching
supply, maybe that somehow affected the dimmer? By the way, the burnout
was one of the HY1707's. Perhaps they actually need a heatsink instead
of just being attached to the circuit board?

That's absolutely all for the Chinese stuff. I had a constant voltage/
current module on the way, but not even going to open it. Can't trust
it anymore.


A device like that needs a proper heatsink. Even if the metal tab is soldered to the PC it's still inadequate for high power applications.


I think that's why they are burning up, then. Nothing else on the board
was fried, only the one Mosfet.
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Old November 23rd 20, 10:17 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

On 11/23/20 4:13 PM, Chuck wrote:
On 11/23/20 4:09 PM, wrote:
On Monday, November 23, 2020 at 3:50:47 PM UTC-5, Chuck wrote:
Well, I have one additional so called "30 amp" Chinese dimmer remaining
after the prior one smoked. This one had a circuit breaker and it did
go today, but not before it started smoking. As I said, I have a good
Astron power supply on the way to replace, but I still had the dimmer in
place until then and outdoors.

This time, I decided to open it up and see what's going on. As others
have said, the Chinese tend to exaggerate ratings so "30 amp" was
probably far from it, but I was surprised what I saw internally:

two HY1707 Mosfets
an LM358
a 78L05
a 555 timer

At 12V, 7 amp load, it seems like it should have been able to handle the
load, but I am wondering that since I was driving it with a switching
supply, maybe that somehow affected the dimmer? By the way, the burnout
was one of the HY1707's. Perhaps they actually need a heatsink instead
of just being attached to the circuit board?

That's absolutely all for the Chinese stuff. I had a constant voltage/
current module on the way, but not even going to open it. Can't trust
it anymore.


A device like that needs a proper heatsink.** Even if the metal tab is
soldered to the PC it's still inadequate for high power applications.


I think that's why they are burning up, then.* Nothing else on the board
was fried, only the one Mosfet.


Going back to my ham radio days, my 2 meter amps of 100 W had heatsinks
of probably 4x6 and an inch or two thick, IIRC. Sometimes even a fan
too. My guess is that would at the very least be needed for these
dimmers and even that heatsink size will get it no where near say 300
W+. Shame on them.

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Old November 23rd 20, 11:39 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

On 2020/11/23 12:50 p.m., Chuck wrote:
Well, I have one additional so called "30 amp" Chinese dimmer remaining
after the prior one smoked.* This one had a circuit breaker and it did
go today, but not before it started smoking.* As I said, I have a good
Astron power supply on the way to replace, but I still had the dimmer in
place until then and outdoors.

This time, I decided to open it up and see what's going on.* As others
have said, the Chinese tend to exaggerate ratings so "30 amp" was
probably far from it, but I was surprised what I saw internally:

two HY1707 Mosfets
an LM358
a 78L05
a 555 timer

At 12V, 7 amp load, it seems like it should have been able to handle the
load, but I am wondering that since I was driving it with a switching
supply, maybe that somehow affected the dimmer?* By the way, the burnout
was one of the HY1707's.* Perhaps they actually need a heatsink instead
of just being attached to the circuit board?

That's absolutely all for the Chinese stuff.* I had a constant voltage/
current module on the way, but not even going to open it.* Can't trust
it anymore.




No UL approval I'm sure.

Why would you trust it then?

Unregulated electrical junk sold on Amazon can be hazardous to your
house or your family.

John :-#(#



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Old November 24th 20, 12:18 AM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

John Robertson wrote:
==================


No UL approval I'm sure.


** What standard is there for such a device the runs on 12- 24V DC ??

Why would you trust it then?


** UL does not check for good design or reliability.


Unregulated electrical junk sold on Amazon can be hazardous to your
house or your family.


**True - but this is not a good example for that.


...... Phil
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Old November 24th 20, 12:49 AM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

On 2020/11/23 3:18 p.m., Phil Allison wrote:
John Robertson wrote:
==================


No UL approval I'm sure.


** What standard is there for such a device the runs on 12- 24V DC ??

Why would you trust it then?


** UL does not check for good design or reliability.


Unregulated electrical junk sold on Amazon can be hazardous to your
house or your family.


**True - but this is not a good example for that.


...... Phil


Fair enough, under - what is it - 32VAC is unregulated...

John ;-#)#
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Old November 24th 20, 03:42 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

https://www.cui.com/blog/what-is-the...-ul-recognized

https://store.intellaliftparts.com/b...abbreviations/

Per the NEC and various codes, powered item permanently installed (in the USA) is required to carry a UL/ETL listing.
Technically, any mains-attached (plug-in) item sold to the public (in the USA) is also required to carry a UL/ETL listing. At whatever operating voltage.
UL Listed items made up of sub-assemblies will typically carry UR symbols on those sub-assemblies. Repairs made to such items must be with UR components.

Where this gets cute: That junk from China is sold from, and originates in China, is typically shipped via subsidized Chinese Post, and directly to the consumer - thereby avoiding the letter of regulations and codes. And then there are here-today-gone-tomorrow resellers that get around the code by simply ignoring it. Making their consumers potential victims.

https://www.galco.com/buy/Staco-Ener...xoCQPcQAvD_BwE This device carries a CSA mark.

https://www.ebay.com/itm/20Amp-Varia...V/124023830503 This device does not. Note the difference in cost. That cost is not only for those obscene profits on the part of the manufacturer, but also for proper design, proper testing, basic quality control, insurance and all the other unnecessary niceties avoided by the resellers and their suppliers. So, the bottom line is that you get what you pay for, with all the consequences attached thereto.

Peter Wieck
Melrose Park, PA
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Old November 24th 20, 03:54 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

On 11/24/20 9:42 AM, Peter W. wrote:
https://www.cui.com/blog/what-is-the...-ul-recognized

https://store.intellaliftparts.com/b...abbreviations/

Per the NEC and various codes, powered item permanently installed (in the USA) is required to carry a UL/ETL listing.
Technically, any mains-attached (plug-in) item sold to the public (in the USA) is also required to carry a UL/ETL listing. At whatever operating voltage.
UL Listed items made up of sub-assemblies will typically carry UR symbols on those sub-assemblies. Repairs made to such items must be with UR components.

Where this gets cute: That junk from China is sold from, and originates in China, is typically shipped via subsidized Chinese Post, and directly to the consumer - thereby avoiding the letter of regulations and codes. And then there are here-today-gone-tomorrow resellers that get around the code by simply ignoring it. Making their consumers potential victims.

https://www.galco.com/buy/Staco-Ener...xoCQPcQAvD_BwE This device carries a CSA mark.

https://www.ebay.com/itm/20Amp-Varia...V/124023830503 This device does not. Note the difference in cost. That cost is not only for those obscene profits on the part of the manufacturer, but also for proper design, proper testing, basic quality control, insurance and all the other unnecessary niceties avoided by the resellers and their suppliers. So, the bottom line is that you get what you pay for, with all the consequences attached thereto.



Yes, I definitely see that now. Unfortunately, I had really hoped to be
able to use one of these dimmers because the linear supply is going to
take up more space, but I will not sacrifice my safety for space. I do
wonder about something like PC power supplies. I have some old Dell
ones, many times used for other purposes (those three voltage rails sure
come in handy sometimes), but none that I can see have any UL listings.
I've had desktop PC's run for years 24/7 without incident. Anything
that ever went bad was usually memory or hard drives and such. I've had
a lot more trouble with laptops (but still not laptop power supplies...
motherboards!), but that's a story for another day.



Peter Wieck
Melrose Park, PA


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Old November 24th 20, 04:05 PM posted to sci.electronics.repair
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Default another dimmer smoked today outside thank goodness!

https://www.cpumedics.com/dell-cpb09...xoCAlsQAvD_BwE


https://www.cpumedics.com/dell-dk87p...hoCExQQAvD_BwE

If sold in the United States:

There will not be a UL mark on a computer power supply.
There will be a UR mark on a computer powers-supply.
If there is neither, it is a knock-off.

The power-supply is a sub-assembly. Not the main event.

Peter Wieck
Melrose Park, PA


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