Phat Australian Playstation 2 Power Supply opinions? - Page 1
Forum section: electronics / repair

author: sausage
author_rank: Regular Contributor
timestamp: May 31, 2021, 10:37:46 am
content: Hi All. I've returned to trying to fix my Australian PAL phat (fat) Playstation 2 console.The current symptoms:PS1 CD games play finePS2 DVD games usually won't load (95% of the time), but if they do, disc loading and running is perfectWhen I first tried to diagnose the issue, I followed many internet guides where the usual suspect is the laser unit that is wearing or needs to be aligned with the cog wheel.I spent some time adjusting and re-testing, and found that the DVD actually got worse, and CD started failing too. So the alignment was best where it started.The other common fault is the laser itself starting to wear, and needs to draw more current. So tweaking the pot to reduce the resistance is a common fix.In my case I opted to replacing the laser unit and the results were identical.I got wind that the Power Supply unit could be the cause. The PCB is a 1468-565-21, and I found an image of the same unit here:There are two 12V pins and two ground pins that connect the PSU to the motherboard. I measured the voltage and it came to 11.90V. That did seem very slightly under. On an oscilloscope the 11.90V is pretty steady but flucuates between 11.89V and 11.92V.But of course that might indicate the available current might be a touch undercooked.I ended up making a jig with thick wires so that I could measure the current draw on the 12V output. The results were:Standby mode: 6mAScreen output with no disc spinning: 2.0 AmpsDisk spinning: 2.2 AmpsDisk seeking and loading: 2.4 - 2.9 AmpsI found it hard to get the expected current draw specs of this Playstation 2, but the service manual indicated a draw of 50W. The maths for this at 12V indicates 4.16 Amps. Am I right here?I am now suspecting that the current needed to kick off the loading of a DVD game needs to rise initially, and the PSU usually can't deliver it.I have done an ESR check over all the big caps on the board and they appear to be nicely low. I plan to desolder them out and test them more thoroughly.But I am now turning my attention to the MOSFET, and after such a lengthy backstory here comes my question:The MOSFET is a K2700 and a datasheet is here:http://www.datasheetcafe.com/k2700-datasheet-mosfet-toshiba/The current drain is 3A with a pulse of 9A.On my multimeter I only ever saw as high as 2.9 A. Is it possible for a MOSFET to weaken or lose it's full drain current over time? Or could some other component cause a lack of total available current though the MOSFET?Any hints would be appreciated. I'm trying to catch my own fish with this.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 31, 2021, 08:07:47 pm
content: From what you state I'd think the main psu is ok, that said the whole machine doesn't run on 12V, so 5, 3.3, etc. must be generated on the motherboard, I'd find and test those rails.

author: ambrosia heart
author_rank: Regular Contributor
timestamp: June 01, 2021, 12:15:17 am
content: download Service manualhttps://elektrotanya.com/sony_playstation_2_scph-70000.pdf/download.html#dlCheck waveforms such as RF and FOK .Optical pickup aging, makes read DVD disc difficulty.ReplacIng optical pick up solves this problem.Download DVP NS900v to compare waveform.

author: pitpat
author_rank: Contributor
timestamp: June 01, 2021, 09:33:41 am
content: Hi!About the math behind the Amperage you are indeed right P=V*I so in your case P/V=I and I=4.166AAnd yes if something has gone bad before the MOSFET imho it could cause a lack of current troughs it, very unlikely though...Can't you find a replacement for the MOSFET? If it's a cheap one i would probably just replace it.In my experience a low ESR isn't always a sign of an healthy capacitor, I would change them if they are a concern to you, they are getting quite old (20 year?).Oi! From ItalyFederico

author: Rasz
author_rank: Super Contributor
timestamp: June 01, 2021, 10:44:06 am
content: why chase ghosts? substitute this supply for a lab one, or ATX, and retest.

author: sausage
author_rank: Regular Contributor
timestamp: June 01, 2021, 01:02:20 pm
content: Thanks everyone for replies. I don't have a bench power supply as yet, but I do have an ATX and can hook that up and rule out the PSU first.Thanks pitpat for confirming my numbers.

author: amyk
author_rank: Super Contributor
timestamp: June 01, 2021, 01:29:44 pm
content: Switching transistors in PSUs are either completely and obviously dead, or working perfectly. I haven't come across ones that would degrade in the way you're thinking.Alternatively, put a few more caps in parallel on the 12V rail, another 3-4mf or so. If it starts working, then the old ones were bad (either high ESR or low capacity.)

author: sausage
author_rank: Regular Contributor
timestamp: June 07, 2021, 11:30:14 am
content: Wanted to say thanks for all the advice in this thread. Hooking up my ATX was a good move. Really happy with that PSU as it's right on the nose a perfect 12.00V output and lots of amperage available.I connected it up to the PS2 and the results were identical.So that elimates the PSU as being the problem in any way, shape or form, which pretty much closes this thread.For general closure, I discovered the cause. I recall I fitted a Messiah 2 modchip something like 20 years ago. Sorry I didn't remember to mention this at the start.When I do a "double reset" press, all games load perfectly. So I'd say the standard "original disc" mode is not working, and when I put the PS2 into the modchip mode it must bypass the disk check on original disks (that's all I own by the way).Thanks everyone for the advice, sorry for the bum steer.