Author Topic: Schematic for Tenma 72-705  (Read 410 times)

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Offline JS_NY1

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Schematic for Tenma 72-705
« on: July 04, 2018, 01:19:29 am »
I recently unearthed a Tenma 72-705 dual laboratory power supply.  One channel works beautifully, the other channel outputs the maximum voltage with no control.  I have a very poor quality schematic for this unit.  Does anyone have a good, clean schematic they could send me?  Thanks, Jim KC2ZVK

Offline Chris56000

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Re: Schematic for Tenma 72-705
« Reply #1 on: July 04, 2018, 06:28:52 pm »

Would you mind posting the poor–quality diagram you do have please?

I might be able to redraw it for you if it really isn't too indecipherable!

Chris Williams
It's an enigma that's what it is!! This thing's not fixed because it doesn't want to be fixed!!

Online bitseeker

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Re: Schematic for Tenma 72-705
« Reply #2 on: July 06, 2018, 02:22:14 am »
Hi JS_NY1,

Welcome to the forum. If that's a linear power supply (I didn't see much with that model number), it sounds like the power transistor on that stuck channel is shorted. Remove it from the circuit and check. If it is shorted, then replace with a similar working transistor. If not, then do comparisons between the good and bad channels.

Although schematics can be helpful, you have the benefit of a working example as reference. You'll probably find the culprit with a little sleuthing.
« Last Edit: July 06, 2018, 02:25:08 am by bitseeker »
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