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Tenma power supply modifications and improvements

This Tenma power supply is really nice designed and small on the desk too

it has a BIG lit display and features like output on/off and its low price and fan less design made be order two

This size design gives 100 Watt of output power, and comes in 3 different max voltages: 20V 36V and 60V
I got mine at FARNELL order codes:
1573428 for the 20V version, 1573427 for the 36V version, 1573426 for the 60V version.

as always several things are not smart, and users must modify things to get it as they like.. I am used to it.
1 display is so much lit you almost need sun glasses to look at it, this will wear LED light fast. (change a resistor value)
2 display refresh rate is almost 1hz ! way to slow, drove me mad after 2 days. (add two speed up resistors)
3 supply is compleetly floating even when you have propper earthing, so potential danger to some circuits (add 1 meg resistor)
4 potentiometer knobs are small and in combination with normal 270 deg potentiometer voltage is hard to adjust (change pot to multiturn)

The case and board is of high quality, the feel and look is good

The front come of easy with a smart press up system, be carefull with the thinn wires and sharp metal edge

Here are the mods performed on the display board:
R37 was 390 ohm the series resistor to LED light, I changed it to 560 ohm, you can go even a bit more up if you like to dimm it more
the two 27k resistors added on pin 1 to 40 on the two big display controllers speed up the display refresh rate
They did a good job with factory adjustment of voltage and current on mine, but here are the two pots to fine adjust if needed

You can desolder the original resistor from the top so you dont have to remove the display board at all.

Solder the new resistors as flat to the board as you can, not much space to the metal when front panel is mounted

Here the earth to ground 1 meg resistor, this will keep the capacitors discharged, so you dont fry critical electronics
also note the potentiometers are kinda cheap type but a little bit too small for the good quality multiturn,
and the shaft is only 4mm or so, so I need to look a bit more to find a good multiturn for those. (10K for the voltage)

no big surprice to see this supply is designed by manson,
I have several other PSU's from manson all needed some kinds of modifications before I was happy

as always you see a TL494, see this is easy stuff to repair and mod if needed.

tenma_modded_and_org.mpg video clip show modded and original update rate. 5MB

Thomas Scherrer OZ2CPU 2009