Tenma "handheld" PSU

[mikeselectricstuff]

Lack of earth is a bit of a concern - output will probably have a lot of common-mode AC noise on it.

[ataradov]

Note that this thing has -0.6V on the output when the output is "Off". Or at least TekPower branded unit does.

[Scratch.HTF]

This model is also marketed under Jaycar cat. MP3844.

[oPossum]

Note that this thing has -0.6V on the output when the output is "Off". Or at least TekPower branded unit does.

The video shows that and has a fix for it.

[ataradov]

The video shows that and has a fix for it.

Thanks for pointing that out. I've applied the fix to my unit and it worked.

[NoisyBoy]

I like the portability, but for that price, we shouldn’t have to “fix” a brand new proud to correct a design defect and void our warranty on our own expense. 

I’d wait for a different product.

[ataradov]

I like the portability, but for that price, we shouldn’t have to “fix” a brand new proud to correct a design defect and void our warranty on our own expense. 
I’d wait for a different product.

I agree. It also has very counter-intuitive UI. I feel like they've got a good version 1 product. But I doubt they will ever follow up on that.

[ataradov]

Just an update on the "fix". I was using this supply with the fix applied in short bursts with low voltages and it was fine. Today I need 15 V and a very little current (basically open). Well, after ~20 minutes I smelled a typical burnt electronics smell. The disassembly of the unit shows that those resistors are burned up.

So the fix does not seem to be very robust.

[screwbreaker]

Just an update on the "fix". I was using this supply with the fix applied in short bursts with low voltages and it was fine. Today I need 15 V and a very little current (basically open). Well, after ~20 minutes I smelled a typical burnt electronics smell. The disassembly of the unit shows that those resistors are burned up.

So the fix does not seem to be very robust.

Thanks for reporting this.

I've just removed the transistor, to get rid off the -0.6V from the output.
I don't care about the discharge time of the capacitors, I don't intend to use it as a precision bench PSU.

By the way my unit was full of this little residual solder balls. Probably the wrong amount of solder paste or, the wrong temperature is used during the production assembly.

With an on/off switch this will be a very nice portable unit.