PS3 PSU (APS-231) Voltage mod

[m111920]

I have this PSU from old broken PS3, it's 23.5A +12V PSU, using it 3 months from now to run a car amp and it works perfectly, but it needs little more boost.

I need help about mod, don't know where to start, which chip..which resistor??

Any help will be appreciated

[domas]

Re: PS3 PSU (APS-231) Voltage mod

there are 3 chips as i can see
uc3854, LM339, cxa8038a

not sure about last one but the controlling chip is uc3854. check it's datasheet. It is different from tl434, so you have to work on in yourself.

[domas]

Re: PS3 PSU (APS-231) Voltage mod

https://cdn.badcaps-static.com/pdfs/...f943b9589e.pdf

maybe pin 11(Vsense) but check what voltage do you have there when p/s is operating normally.

And do this at your own risk as i am no expert.
By the way by more boost you mean more voltage??

[Behemot]

Re: PS3 PSU (APS-231) Voltage mod

There is a couple of potentiometers, there is high probability one of them is for voltage tuning.

[m111920]

Re: PS3 PSU (APS-231) Voltage mod

there are 3 chips as i can see
uc3854, LM339, cxa8038a

not sure about last one but the controlling chip is uc3854. check it's datasheet. It is different from tl434, so you have to work on in yourself.

I think that too

https://cdn.badcaps-static.com/pdfs/...f943b9589e.pdf

maybe pin 11(Vsense) but check what voltage do you have there when p/s is operating normally.

And do this at your own risk as i am no expert.
By the way by more boost you mean more voltage??

from datasheet: "VSENSE (Pin 11) (voltage amplifier inverting input): This is
normally connected to a feedback network and to the
boost converter output through a divider network"

Cloud be it?

There is a couple of potentiometers, there is high probability one of them is for voltage tuning.

Tried all of them, no-no

[domas]

Re: PS3 PSU (APS-231) Voltage mod

well, as i mentioned i am no expert here. but try adding a trimpot there in series between pin11 and its circuitry on pcb, and set it to 0ohms when you power it up, and then carefully try to adjust the voltage - see if it increases. Remember, if you manage to break the feedback circuit somehow, the voltages will skyrocket unless there is an additional protection and blow some electrolytic caps on the output side ;-)

[Khron]

Re: PS3 PSU (APS-231) Voltage mod

I would seriously recommend AGAINST messing around on the primary side of the circuit...

A far better choice would be finding the TL431 that's hooked up to one of the optocouplers (which is responsible for the voltage regulation feedback) - i think i might've found it, but you'll have to confirm the markings. It might be one of the two small SOT23 3-pin IC401(?) or IC201, near the top left corner of the board, right on the left edge, "above" that 6.3mm or 8mm ChemiCon cap, and "facing" the bottom-most two of those four optocouplers.

Just keep in mind, one of them may well be for the 5Vsb, and the other one for the 12v rail. If you can read the values of the 2-3 resistors connected to each of those 3-pin chips, that can easily be determined

[domas]

Re: PS3 PSU (APS-231) Voltage mod

I would seriously recommend AGAINST messing around on the primary side of the circuit...

A far better choice would be finding the TL431 that's hooked up to one of the optocouplers (which is responsible for the voltage regulation feedback) - i think i might've found it, but you'll have to confirm the markings. It might be one of the two small SOT23 3-pin IC401(?) or IC201, near the top left corner of the board, right on the left edge, "above" that 6.3mm or 8mm ChemiCon cap, and "facing" the bottom-most two of those four optocouplers.

Just keep in mind, one of them may well be for the 5Vsb, and the other one for the 12v rail. If you can read the values of the 2-3 resistors connected to each of those 3-pin chips, that can easily be determined

what? since when hacking feedback circuit is working on hot side??
I just do not understand why playing with optocouplers is better idea than playing with the control chip itself.

I am sure you have seen some examples of doing the same to TL494, where you add a trim pot on the first pin. I am trying to apply same practice to uc3854 which is similar chip to tl494, but not pin-to-pin compatible.

The idea i am offering for him is reducing the Vsense input to the chip itself, thus UC chip will try to compensate for faked "missing" voltage, therefore increasing the voltage.

[m111920]

Re: PS3 PSU (APS-231) Voltage mod

I've measured resistance between Vsense (11) pin and ground, it was 6.41k. then i added 100K pot in parallel, at the end, resistance was 6.30K and power supply didn't turn on.

[domas]

Re: PS3 PSU (APS-231) Voltage mod

any damage to p/s?

what is the voltage on pin 11 when p/s is operating normally? To increase the voltage you probably should increase the resistance, therefore to connect something in series

[domas]

Re: PS3 PSU (APS-231) Voltage mod

ok, now i just thought about what Khron666 had in mind...

As i looked to datasheet of UC chip again, it is a preregulator (APFC in atx terms i guess?), as in typical application note. The functionality is similar to pwm driver but it is not the same..

I guess there is another chip controlling the output. I doubt that only UC chip is responsible for both preregulation and output voltage. As i check the nets, it most likely is cxa8038a, but there is no datasheet for it.

[Khron]

Re: PS3 PSU (APS-231) Voltage mod

I believe the method i recommended was the safest, and the one with the greatest chances of success. Adding to that the lack of a datasheet for that CXA8038A, it's starting to seem like the only way

Then again, i've found 2 pages (with not much on them) for a CXA8038P:

And yes, it seems that UC3854 is "just" the APFC controller (not "just" in ATX terms ).

In the first picture from the first post, i can read "12V REG" right next to optocoupler PH301 - see if any of its two leads from the secondary side go to IC401(?) or IC201, then see what resistors are connected to that one - one will have one end going to the +12v rail, and the other one will have one end going to ground; the two remaining resistor ends should be joined together, and going to one of the pins on IC401 or IC201, whichever's responsible for regulating the 12v rail.

[domas]

Re: PS3 PSU (APS-231) Voltage mod

nice job with finding the datasheet, it seems that pinout is what we need.

according to datasheet it looks like it should be pin 4, but i am not too sure about it.

m111 please check how much voltage in relation to GND and pin 16 do you have on that pin 4 when p/s is operating normally.

I am just unsure why do we have an octocoupler on 12v reg., from my experience feedback circuit is just a resistor going from 12v line

[m111920]

Re: PS3 PSU (APS-231) Voltage mod

i will check today,im busy right now,sent this from cellphone

[Khron]

Re: PS3 PSU (APS-231) Voltage mod

I am just unsure why do we have an octocoupler on 12v reg., from my experience feedback circuit is just a resistor going from 12v line

Well, don't take this the wrong way, but that means your experience is a bit "insufficient". I'd say 9 times out of 10, in an off-line (ie. line-powered, isolated) REGULATED switching power supply, the feedback to the PWM controller (especially when it's on the primary side) is done with the help of a TL431 (or similar) chip.

True, there's a resistor coming from the regulated rail in series with the diode in the optocoupler, but between the diode and ground, there's a TL431

[domas]

Re: PS3 PSU (APS-231) Voltage mod

I don't, no worries here, the knowledge definately is insufficient. Well thats getting offtopic, but by saying line regulated/off-line do you mean that the P/S does not have a standby transformer? Or i still misunderstand the conception? Because the particular p/s has 5Vsb.

I will have to do some reading later tonight anyway, i have some documents about topologies, i can maybe go through those. Well thats not what this thread is about

[Khron]

Re: PS3 PSU (APS-231) Voltage mod

"Off-line" = line-powered, from 110/120/220/230V AC, as in 'NOT a DC-input SMPS'

Regulated = has feedback from the output (if the controller is on the primary side, it's gonna have at least ONE optocoupler)

Non-regulated = i know my definition's not entirely accurate, but that's what i call the ones that only have feedback from the auxiliary winding on the primary (that's also supplying the PWM chip)

Either way, especially since there's something that may well be a TL431-type part near that group of optocouplers, plus the lack of information about the PWM chip, i still maintain that the safest, most "certain" and most likely to work method of modifying the output voltage of this particular PSU is to alter the feedback. And to that, i can add my reservations about poking around the primary side of an SMPS

Call me weird, but isn't it easier (not to mention safer - 230VAC and/or 320-385VDC isn't fun to mess around with) to try something that's safer and more likely to work, than to just try semi-random stuff, "in the dark"?

[m111920]

Re: PS3 PSU (APS-231) Voltage mod

there is 0 ohm resistance between optocoupler's second pin and ic401 first pin

[Khron]

Re: PS3 PSU (APS-231) Voltage mod

IC401 - marking L287 = TS2431

https://cdn.badcaps-static.com/pdfs/...72f58e3dcc.pdf

See what resistance value you can measure between pins 1 and 2, and then 3 and 2 (see datasheet in the link for pin numbering).

To increase the output voltage, you'll need to decrease the resistance between pins 2 and 3 (formula in Figure 11 in datasheet).

[m111920]

Re: PS3 PSU (APS-231) Voltage mod

there is 6.20K ohm between 1 and 2 and 800ohm between pins 2 and 3
btw I just meant to do the same thing!