Comments on: Finding And Replacing Faulty Capacitors – Switch-Mode Power Supply Repair Hints http://mark-lawton.com/replacing-faulty-capacitors-switchmode-power-supply/?utm_source=rss&utm_medium=rss&utm_campaign=replacing-faulty-capacitors-switchmode-power-supply The Generalist's Repository Thu, 02 Feb 2012 07:28:49 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Mark Lawton http://mark-lawton.com/replacing-faulty-capacitors-switchmode-power-supply/comment-page-1/#comment-1177 Mark Lawton Wed, 01 Sep 2010 21:56:28 +0000 http://mark-lawton.com/?p=1575#comment-1177 I have a new blog that may be appropriate... http://mark-lawton.com/speed-control-phase-angle-dimmer/ Enjoy... and be careful with line or mains projects! Mark Lawton I have a new blog that may be appropriate…

http://mark-lawton.com/speed-control-phase-angle-dimmer/

Enjoy… and be careful with line or mains projects!

Mark Lawton

]]> By: Mark Lawton http://mark-lawton.com/replacing-faulty-capacitors-switchmode-power-supply/comment-page-1/#comment-1168 Mark Lawton Wed, 01 Sep 2010 17:32:17 +0000 http://mark-lawton.com/?p=1575#comment-1168 Hi there Steve, That's a good question. Easy ways that may work... Use a cheap dimmer switch before or after the transformer. My favorite cheap way of controlling the phase angle of the mains and thus reducing the voltage is to buy a simple thick film controller chip from RS components. RS Stock No. 307-957 (www.rswww.com) or any good supplier. Build the circuit as they show it, simple! I have built one into a metal 3 pin 240V mains socket for speed reduction, and lamp dimming. Earth the body which is an isolated tab, and the metal socket acts as a heat-sink. Fit a potentiometer to it as shown, and you can vary the output a lot. Adjust it to get what you want. It works on AC motors, lamps and all sorts of stuff. You still get AC coming out, so you are OK with inductive loads. If it is a permanent installation, you can fit a fixed resistor, or a trimmer, and mount the whole thing on Vero board, and fit a heat- sink to the device. Another way, you could go direct in with mains, and rectify the output and smooth it. Obviously you'll need a 1:1 isolation transformer before the unit as otherwise you have no mains isolation, so it can be done. Use a very fast acting semiconductor fuse to protect the controller if you so wish, and is recommended. Other ways involve using switching regulators like in a TV set, with many components, and much design needed, but the way above is simple, cheap and straightforward, but the switcher isnt so straightforward. Don't forget your DC will go up when smoothed ((square root of 2) x RMS voltage output), and use a high value bleed resistor to discharge the capacitor slowly once it is switched off, and to avoid a nasty shock if it is still charged up, (say 100K 3W). Mark Lawton Hi there Steve,

That’s a good question.

Easy ways that may work…

Use a cheap dimmer switch before or after the transformer.

My favorite cheap way of controlling the phase angle of the mains and thus reducing the voltage is to buy a simple thick film controller chip from RS components.

RS Stock No. 307-957 (www.rswww.com) or any good supplier.

Build the circuit as they show it, simple!

I have built one into a metal 3 pin 240V mains socket for speed reduction, and lamp dimming.

Earth the body which is an isolated tab, and the metal socket acts as a heat-sink.

Fit a potentiometer to it as shown, and you can vary the output a lot.

Adjust it to get what you want. It works on AC motors, lamps and all sorts of stuff. You still get AC coming out, so you are OK with inductive loads.

If it is a permanent installation, you can fit a fixed resistor, or a trimmer, and mount the whole thing on Vero board, and fit a heat- sink to the device.

Another way, you could go direct in with mains, and rectify the output and smooth it.

Obviously you’ll need a 1:1 isolation transformer before the unit as otherwise you have no mains isolation, so it can be done.

Use a very fast acting semiconductor fuse to protect the controller if you so wish, and is recommended.

Other ways involve using switching regulators like in a TV set, with many components, and much design needed, but the way above is simple, cheap and straightforward, but the switcher isnt so straightforward.

Don’t forget your DC will go up when smoothed ((square root of 2) x RMS voltage output), and use a high value bleed resistor to discharge the capacitor slowly once it is switched off, and to avoid a nasty shock if it is still charged up, (say 100K 3W).

Mark Lawton

]]> By: steve oxborough http://mark-lawton.com/replacing-faulty-capacitors-switchmode-power-supply/comment-page-1/#comment-1165 steve oxborough Wed, 01 Sep 2010 14:51:17 +0000 http://mark-lawton.com/?p=1575#comment-1165 I need a power supply that can be powered by 230V -240V input and 110V DC output @ 10A I have a mains isolation transforner at the moment which is rated at 240V input 110V output with a standard brige rectifyer rated at 10.8A which when measured gives me an output of 122V dc which is too high and not very smooth obviously, I could conect a cap to the output to smooth out but the output gets even higher, I have no way of varying the input voltage. What if any can you sugest please I need a power supply that can be powered by 230V -240V input and 110V DC output @ 10A

I have a mains isolation transforner at the moment which is rated at 240V input 110V output with a standard brige rectifyer rated at 10.8A which when measured gives me an output of 122V dc which is too high and not very smooth obviously, I could conect a cap to the output to smooth out but the output gets even higher, I have no way of varying the input voltage. What if any can you sugest please

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