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Old 11-25-2013, 12:01 PM   #21
Khron
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Default Re: PS3 PSU (APS-231) Voltage mod

6.2ohm is terribly low, for that resistance. Have you measured that with the probes both ways?
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Old 11-25-2013, 12:37 PM   #22
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Default Re: PS3 PSU (APS-231) Voltage mod

IT WORKS! thanks everyone.
Now how to remove OVP to 15V?
Is it possible to make PSU to turn off at 15V or i must remove OVP completely?
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Last edited by m111920; 11-25-2013 at 12:39 PM..
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Old 11-25-2013, 12:40 PM   #23
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Default Re: PS3 PSU (APS-231) Voltage mod

Quote:
Originally Posted by Khron666 View Post
6.2ohm is terribly low, for that resistance. Have you measured that with the probes both ways?
Sorry, edited post now
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Old 11-25-2013, 01:34 PM   #24
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Default Re: PS3 PSU (APS-231) Voltage mod

6.2k makes a lot more sense Congrats

The OVP is most likely implemented somewhere around the PWM, on the primary side - logic would dictate that the LM339 is most likely used for that (as well as other functions), so i'm afraid i'm / we're a bit stuck, regarding that...
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Old 11-26-2013, 02:14 AM   #25
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Default Re: PS3 PSU (APS-231) Voltage mod

Khron thanks for definitions.
And no my original idea was not to alter hot side.. I made a mistake, i assumed that preregulator was pwm controller after a quick look in the datasheet. Therefore i decided to hack its feedback, while my goal was to alter feedback circuit for pwm driver, exactly as it was done here.

Regarding OVP, LM339 does indeed have 4 comparators inside that are most likely for protections. From my experience in ATX modding i would say that altering feedback doesn't trigger OVP for some reason (i guess it changes the reference voltage which maybe comes from the feedback signal?). The zener diodes (or other crowbar protection components) can do it though, so check the output side as well.

Of course remember to check cap voltage rating on the output, as you don’t want to exceed those.

If there are no crowbar protections on the output, lm339 is really simple chip, what i would do is i would get some help (few more hands or so), and find out which one of 4 comparators are used for OVP by checking voltages on input pairs while increasing output voltage with trim pot.

find out which IN+ (or IN- but i don't think so) increases together with voltage, and OVP should trigger as soon as in+ is as high as IN- (for the same comparator).
The input pairs on LM are following: pins 4 and 5; 6 and 7; 8 and 9; 10 and 11; giving outputs to pins 2; 1; 14; 13, respectively.
pins 3 and 12 are Vcc and GND, respectively.
Then fake that voltage or disconnect input pin or something.

Thats just an idea. you don't want to disable OCP though
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Old 11-26-2013, 07:08 AM   #26
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Default Re: PS3 PSU (APS-231) Voltage mod

Best thing to do is to make psu shutdown at 15.5v for safety of capacitors and load, best voltage for powering car amp is around 15V. My idea is to increase resistance little bit at comparator 's voltage input, if it's posible.
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Old 11-26-2013, 07:25 AM   #27
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Default Re: PS3 PSU (APS-231) Voltage mod

I did not see what is the current OVP level? And cap ratings, are they 16V?

I don't see any reason for running car amp at more than 13-14V. For lead-acid battery it might be needed as voltage drops quite a bit when you load it. While this is a regulated p/s it should keep up with voltage at different loads unless you push it to the max.

i run my adjustable atx until 15,5V as well. I did not need to adjust anything on the comparator as it worked fine from the very start. I have limited it with a adjustable resistor so on extreme setting on trim pot (max voltage) it is 15.5V
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Old 11-26-2013, 09:01 AM   #28
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Default Re: PS3 PSU (APS-231) Voltage mod

OVP triggers at 14v, caps are 16v,
PSU voltage is at 13.7v now, fixed resistor soldered.
I would be satisfied with 14.4v

BTW amp is rated at 200W @ 4ohm load and 350W @ 2ohm load measured at 14.4v, I'll be using a 4 ohm sub.
It's a D-class and it is very efficient
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Old 11-26-2013, 02:51 PM   #29
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Default Re: PS3 PSU (APS-231) Voltage mod

I have measured voltages on LM339 and there was change only in pin 6, after disconnecting pin6 from board, no changes were made, I also tried to remove CXA8038's OVP control pin and same thing...ideas?
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Old 11-27-2013, 02:30 AM   #30
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Default Re: PS3 PSU (APS-231) Voltage mod

Okay, i am more interested in what is the difference between pins 6 and 7 when you get closer to triggering the ovp.


Else check for crowbar protections on the output
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Old 11-27-2013, 03:43 AM   #31
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Default Re: PS3 PSU (APS-231) Voltage mod

pin 6 3.60v pin 7 2.50v, doesn't make sense. What exactly should I look for at crowbar protection?
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Old 11-27-2013, 03:55 AM   #32
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Default Re: PS3 PSU (APS-231) Voltage mod

zener diodes on the output is a popular solution
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Old 11-27-2013, 04:46 AM   #33
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Default Re: PS3 PSU (APS-231) Voltage mod

Can't find any :/
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Old 11-27-2013, 04:57 AM   #34
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Default Re: PS3 PSU (APS-231) Voltage mod

then please go back to testing LM339,
Output pins: 2; 1; 14; 13, please check their voltage in relation to GND.
Try checking one that changes when ovp is triggered.
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Old 11-27-2013, 05:06 AM   #35
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Default Re: PS3 PSU (APS-231) Voltage mod

Quote:
Originally Posted by domas View Post
then please go back to testing LM339,
Output pins: 2; 1; 14; 13, please check their voltage in relation to GND.
Try checking one that changes when ovp is triggered.
Already did everything, I will repeat just in case.

EDIT:

pin 1-0.14v
pin 2-0.06v
the following pins have a little bit change when I change resistance from 12v to 13.7v
pin13 0.04v and 0.05
pin14 3.56v and 3.58v

Last edited by m111920; 11-27-2013 at 05:54 AM..
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Old 11-27-2013, 06:11 AM   #36
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Default Re: PS3 PSU (APS-231) Voltage mod

try measuring voltage while adjusting voltage AND overvoltaging the p/s? any of those that change significantly at the moment of ovp?
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Old 11-27-2013, 08:26 AM   #37
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Default Re: PS3 PSU (APS-231) Voltage mod

pin13 goes about to 0.41v for a fraction of second
pin13 just goes down
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Old 11-27-2013, 01:02 PM   #38
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Default Re: PS3 PSU (APS-231) Voltage mod

Quote:
Originally Posted by m111920 View Post
pin13 goes about to 0.41v for a fraction of second
pin13 just goes down
so pin 13 increases for a second and gos to 0.00V afterwards?

Try tracing pins 10 and/or 11 to 12v output
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Old 11-27-2013, 05:34 PM   #39
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Default Re: PS3 PSU (APS-231) Voltage mod

pin 10 2.48v
pin 11 2.18v

i will continue tomorrow

Last edited by m111920; 11-27-2013 at 05:44 PM..
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Old 11-27-2013, 06:13 PM   #40
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Default Re: PS3 PSU (APS-231) Voltage mod

tracing, not measuring but if you want to measure them, check if those pin voltages get close to each other when getting closer to ovp level. Else try making very clear pictures of both sides of the board so some of us can try to look into that
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