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lab power supply, anyone any experience fixing them

Posted: Tue Jan 07, 2014 11:32 pm
by glyndwr1998

not sure if this is in the right section, but here goes,

I got a Tenma lab type switch mode power supply that i was using to manually balance my 76 cell lithium battery pack. The power supply is a tenma 72-2085, qnd its a 0-30v 0-5a power supply.

It was working beutifully until i had a little accident with it.

I have made a distibution board that has got 76 banana plug sockets fitted to it, i did this to make test access to each battery much easier, and not have to get any where near the 250v dc battery pack whilst doing any manual balancing, as i havent fitted a BMS, i use cell loggers and do cell monitoring instead.

Anyhow, after i was topping up the charge in 1 cell, when i removed one of the banana plug leads from the socket whilst the other banan plug lead was still inserted in that cell socket, it unbeleivable rested and touched another cell banana socket over sending over 40 volts DC back into the power supply.
Now, the lab supply powers up still works, but only on max voltage output, which is 48v, there is no adjustment possible.

I have changed the motorolla voltage regulators shown in the pics 2n3055, there are 4 of these, but it made no difference.

I have taken pics of the unit and the pcb, with the hope that someone may have knowledge on what may have to be changed to get it working properly again. I can solder components into the pcb ok, and can use a meter ok to check individual components if necessary.

Any help is greatly appreciated.

Many thanks, Anthony.

Re: lab power supply, anyone any experience fixing them

Posted: Tue Jan 07, 2014 11:52 pm
by glyndwr1998
Ill have to upload the pics tomorrow as the ones i have taken are too large to upload.