ATX PSU Tester Analyzer modification / upgrade

[stj]

Re: ATX PSU Tester Analyzer modification / upgrade

so before it gets out of hand,
lets decide how bad the 5v can be.

personally i think it should be checked seperatly first.
ripple will be an issue - it will mess with voltage regulators - BUT if you smooth it then your effecting the reading the meter will give you.

[eccerr0r]

Re: ATX PSU Tester Analyzer modification / upgrade

That can be mitigated, definitely need diode isolation.

[momaka]

Re: ATX PSU Tester Analyzer modification / upgrade

Cool mod, Rich. I probably wouldn't have the nerves to spend as much time modding such a tester, as I find these are pretty useless for testing PSUs. Probably the only useful thing they measure is the PG delay.

Now, if combining one of these testers with a resistive load tester for the PSU's output rails, that might actually be useful to see how the voltages from the PSU behave. Add an o-scope on the output of the PSU, and you have an inexpensive and more or less proper PSU tester.

I really don't know why they used 12V to power initially, seems that you should be able to use 5VSB for nearly no additional cost, granted it will require it to be at least 3 or 4 volts for it to power whatever chips the tester uses. As said multiple times, ATX PSUs that don't have 5VSB working cannot turn on because that's what powers the !PSON - for both isolation and for keeping voltages within reasonable limits. Note that in the normal case, motherboards need 5VSB to power their switching circuitry, can't assert !PSON without any power.

+1

Can't think of any reason not to power off of 5VSB other than if your meter draws more than 100mA - because ATX1.0 did not specify much current for 5VSB.

Agreed... though I think even most old ATX PSU's could do at least 500 mA to 1 Amp, so I don't think that should be an issue here.

Hopefully bad cap ripple on 5VSB doesn't blow the tester...

Yes, that, or over-voltage like might happen with PSU's with 5VSB circuits similar to the suicidal Bestec ATX-250-12E. But even then, that should be pretty easy to take care of with a regulator of some sort inside the tester. I imagine even something simple like a series resistor and cap should work just fine to mitigate any ripple, and then perhaps a 5.8V Zener diode (5.1 Zener + regular diode in forward mode in series) to shunt anything over 5.8V to ground, in case the 5VSB does decide to go crazy.

not that brand though - no DuraLeak.

+1
Avoid Duraleaks and Durabulges.

IME, at least, their 9V batteries don't leak (too much), but frequently bulge to the point where I have to pry them out with a big fat screw driver, because they got stuck.
The AA and AAA's are absolutely terrible leakers, though - rarely they last more than 6 months on the shelf. The last AAA's my mom bought for her MP3 player that she takes sometimes when walking around, started leaking just within 3 months of purchase.

But anyways, that's besides the topic discussed here.

[dicky96]

Re: ATX PSU Tester Analyzer modification / upgrade

Yes, that, or over-voltage like might happen with PSU's with 5VSB circuits similar to the suicidal Bestec ATX-250-12E. But even then, that should be pretty easy to take care of with a regulator of some sort inside the tester. I imagine even something simple like a series resistor and cap should work just fine to mitigate any ripple, and then perhaps a 5.8V Zener diode (5.1 Zener + regular diode in forward mode in series) to shunt anything over 5.8V to ground, in case the 5VSB does decide to go crazy.

Errmm, I believe the use of the boost converter also mitigates against this sort of problem as the 'delicate' electronics are hidden behind both the boost converter and the original LDO

[momaka]

Re: ATX PSU Tester Analyzer modification / upgrade

Errmm, I believe the use of the boost converter also mitigates against this sort of problem as the 'delicate' electronics are hidden behind both the boost converter and the original LDO

True.

I just tend to favor solutions with less/minimum parts, and highly preferably stuff I already have in my scrap bin so I can recycle components. Of course, I do like those tiny little boards from Ebay a lot (be it boost, buck, LDO, or any other type of converters and whatnot) as they tend to do a really good job for what they are made for. I feel like I cheated a little every time I use one, though. That's probably just me being weird, though. Hence my suggestion for the RC low-pass circuit and Zener reg/protection.

I suppose as the saying goes, there's more than one way to skin a cat.