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Thurlby Thandar RSComponents Bench Power Supply

I have an old 30V 2A bench power supply badged RS Components Code 610-461 which was made by Thurlby, now Thurlby Thandar Instruments (tti). The current meter shows OFL which I found out means overload. It has linear regulation using a couple of 3055s and looks similar to the EL series on the tti UK website

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Internally it is very similar to an RS Components 610-477 although that is a dual 30V 1A power supply. I have given it a quick check and can't see anything obviously wrong. Does anyone have a schematic or any other info that might help me repair it?

Thanks

John

Reply to
johnwass
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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.

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Adrian C
Reply to
Adrian C

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

610-461
Reply to
johnwass

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)

Reply to
Ron(UK)

Always

swapping

Reply to
johnwass

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 ...

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Adrian C
Reply to
Adrian C

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

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Please remove one \'i\' from my address when replying by email.
Reply to
Franc Zabkar

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