Thurlby Thandar RSComponents Bench Power Supply

On my Thurlby's (considerably older though), OFL means you have the current limit control set fully clockwise equating to the 'no current limit' setting (let me smoke & catch fire first....). This when the power out switch is off.

Try turning the control down? Could be the control itself is faulty if no change.

Adrian

Thanks. However, current limit control setting makes no difference. Always shows OFL. Thought it was unlikely to be the control but I will try swapping it for a different one to see if it makes any difference.

John

That happened to mine (Thandar TS3021S) There was a diode soldered directly across the output terminals which was shorted - I suspect someone had use it to charge a gelcell and connected it up the wrong polarity.

Ron(UK)

Always

swapping

OK. If your assertion that the OFL display means overload is correct, I'd take that to mean that its an indication from the display modules built-in ADC that there is excess voltage at it's input compared with it's specifications for full scale 'deflection'.

Can you see what part they used, find a datasheet and trace the input pin(s). Then stick a meter there, attach a load and see if on varying the output voltage if there is anything sensible changing for these inputs.

I'm guessing all of the circuitry still is plain discrete analogue driven (compared with my old PL154) and you might find the culprit through simple fault finding. If it is a silicon jungle chip maybe not. Though a manual has to be found from somewhere ...

On Fri, 26 Sep 2008 22:56:36 +0100, "johnwass" put finger to keyboard and composed:

If your PSU senses the current via a low ohms series resistor, then an open resistor may produce the observed symptom. In any case it may be a good place to start troubleshooting.

- Franc Zabkar