S
Spehro Pefhany
- Jan 1, 1970
- 0
An associate bought this for me (from a kind of flea market/surplus
shop), just because he thought it looked amusingly gawd-awful. I have
to agree.
It's an allegedly 1600W 240->120VAC adapter for resistive loads.
http://www.speff.com/pcb_view.jpg
http://www.speff.com/resistor.jpg
http://www.speff.com/side_and_cover.jpg
http://www.speff.com/top_view.jpg
The circuit is straightforward.. a simple preset phase control. The
firing angle is determined by a 15K fixed resistor in series with a
50K trimpot and a 0.1uF film cap (it should be around 115 angular
degrees). There's a diac and a BT137 triac.
http://www.nxp.com/documents/data_sheet/BT137_SERIES.pdf
First thing, the cover just lightly snaps on/off; a child or careless
adult could easily remove it. Looks like cheap non-fire-retardant
styrene.
The gold anodized heat sink housing is nicely made, perhaps thicker
than it needs to be. There is no reason for the 15K resistor to be as
large as it is.. it's just acting as a jumper. The triac is
more-or-less held in contact with a ~1/3mm thick silicone heat pad and
thus the heat sink, but only by the springiness of the leads. Given
that the triac is a barely heat-sinked 8A triac.. I suppose it's a
good thing that the fuse in series with the output is 5A. At least
it's a 250VAC fuse. Either the insulation around the resistor or that
on the triac could easily slide out, leaving the metal case connected
to the mains. The bottom of the PCB has a thin (~0.004") insulator,
and creepage distance at the pins is well under 2mm. Yet they bothered
to put thread lock on both the nuts holding the pins to the PCB.
Total horrorshow. The really sad thing is that they could have used
similar materials and components and made a pretty good (and fairly
safe) 500W converter for not much different cost.
Best regards,
Spehro Pefhany
shop), just because he thought it looked amusingly gawd-awful. I have
to agree.
It's an allegedly 1600W 240->120VAC adapter for resistive loads.
http://www.speff.com/pcb_view.jpg
http://www.speff.com/resistor.jpg
http://www.speff.com/side_and_cover.jpg
http://www.speff.com/top_view.jpg
The circuit is straightforward.. a simple preset phase control. The
firing angle is determined by a 15K fixed resistor in series with a
50K trimpot and a 0.1uF film cap (it should be around 115 angular
degrees). There's a diac and a BT137 triac.
http://www.nxp.com/documents/data_sheet/BT137_SERIES.pdf
First thing, the cover just lightly snaps on/off; a child or careless
adult could easily remove it. Looks like cheap non-fire-retardant
styrene.
The gold anodized heat sink housing is nicely made, perhaps thicker
than it needs to be. There is no reason for the 15K resistor to be as
large as it is.. it's just acting as a jumper. The triac is
more-or-less held in contact with a ~1/3mm thick silicone heat pad and
thus the heat sink, but only by the springiness of the leads. Given
that the triac is a barely heat-sinked 8A triac.. I suppose it's a
good thing that the fuse in series with the output is 5A. At least
it's a 250VAC fuse. Either the insulation around the resistor or that
on the triac could easily slide out, leaving the metal case connected
to the mains. The bottom of the PCB has a thin (~0.004") insulator,
and creepage distance at the pins is well under 2mm. Yet they bothered
to put thread lock on both the nuts holding the pins to the PCB.
Total horrorshow. The really sad thing is that they could have used
similar materials and components and made a pretty good (and fairly
safe) 500W converter for not much different cost.
Best regards,
Spehro Pefhany