Re: Ricoh SP 150w PSU repair
Sorry I'm far from an expert.
You're right, it probably bypasses some protection...
Am I correct to assume that the TL431 is good if it outputs 2.5V?
I used the method suggested by LER here [url]https://www.youtube.com/watch?v=LvGehyWLS80[/url]
Any suggestions on what else to test?
ThanksRe: Ricoh SP 150w PSU repair<br />
... outputs 2.5V?
herved
Member
Last Activity: 10-10-2023, 07:09 PM
Joined: 10-15-2015
Location: Belgium
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Re: Ricoh SP 150w PSU repair
I'm also interested to hear if anyone has theories about what caused this PSU to blow up though. Do MOSFETS just short like this usually? Because of age? or voltage spikes? Lack of protection in the circuit design?
It blew up upon pressing the power button.Leave a comment:
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Re: Ricoh SP 150w PSU repair
SUCCESS !!! The PSU and printer are now working!
I read several people who had to chop off (or lift) pin 5 after getting a replacement OB2283 PWM controller chip.
Which I eventually did in a desperate attempt, after testing literally EVERYTHING on this board.
And... it works now.
I don't know if there is any impact doing so though... Anyone knows?
I guess it is not exactly the same chip as the one that was there originally.
I had ordered it on aliexpress here [url]https://www.aliexpress.com/item/33045121475.html[/url]...Leave a comment:
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Re: Ricoh SP 150w PSU repair
I just tested the TL431 (5V on Ref and Cathode and I get 2.5V out).
So I assume it is ok. I don't see any reason to replace it, don't have any in stock either.
Thanks,
HervéLast edited by herved; 11-11-2022, 11:59 AM.Leave a comment:
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Re: Ricoh SP 150w PSU repair
I put the PSU back in the printer but it is not starting.
Before replacing the caps I tried to put a load (24V motor) but it didn't work either (I could try again). Hence why I'm also wondering about this "AC test" pin.
I'm thinking something else is bad in this PSU but I reached my limit on how to troubleshoot it. I don't know what else to check, I believe I tested most components on this board.Leave a comment:
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Re: Ricoh SP 150w PSU repair
Ok I replaced both caps, I still get ~6.3V on VCC of that PWM chip.
But I do get some output voltages in fact:
- 3,4V on "+24VS"
- 2.7V on "AC test" which seems to be "pulsing" to a higher voltage (+24V?) every 2 seconds or so
I wonder what that "AC test" means.
Is this a switch to turn it on by shorting it to ground or similar? Like on an ATX PSU?
I can't really understand the board/schematic.
It goes to a transistor marked (K1N D1) which is connected to...Leave a comment:
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Re: Ricoh SP 150w PSU repair
C807 (markings 2,2 uF, 50V) => 2,371 uF | ESR=1,52 Ohms
C833 (markings 10 uF, 50V) => 10,22 uF | ESR= 0,49 Ohms
C803 main cap (markings 47 uF, 450V) => 43,01 uF | ESR= 0,63 OhmsLeave a comment:
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Re: Ricoh SP 150w PSU repair
Here are in-circuit measurements:
- R826 = 10K (looks ok)
- D804 = 0.52 Vdrop and blocking in the other dir (looks ok)
- R804-805-824-812 = all read ~0.70-0.75M (looks ok)
I also checked carefully this path earlier.
Here are the voltages when the board is powered on to 230V.
Isn't it what a PWM controller is an SMPS does? Like we have here?
I'm a noob please correct me if I'm wrong
...
Leave a comment:
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Re: Ricoh SP 150w PSU repair
Ah , sorry that image - 1665789398015 (1).jpg - is a bit outdated.
I replaced R827, it is now there, see 1667434197.jpg.
It is a 470 Ohm resistor.Leave a comment:
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Ricoh SP 150w PSU repair
Hello everyone,
I'm trying to repair a 24V PSU from a Ricoh SP 150w printer.
So far I found and replaced:
- a burnt 33Ohms 1W resistor (R820 - top side next to main cap)
- a shorted mosfet (Q801 - top side on heatsink)
- 2 shorted optocouplers (U801, U201 - top side)
- a burnt/chipped? (didn't read any resistance) SMD resistor (R828 - back side next to the PWM IC)
- the PWM controller (IC801 - back side)
There is no output voltage at all.
I do get a stable voltage at the main capacitor (320V) but I think the PFC is... -
Re: LG W2234S Repair Help...
Hello everyone,
I have now reprogrammed that chip several times and it always gets corrupted again after a few hours of using the monitor.
I already replaced some of the caps on the PSU (but not all).
What would you recommend? What could be causing the flash chip to get corrupted?
Replace all caps on the PSU?
Could it be caused by the crystal on the logic board?
Could this be a software bug?
ThanksLeave a comment:
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Re: New Members - please post your introductions here
Hello everyone, I subscribed some time ago but didn't activate my account yet.
I like to repair electronics when possible and the information/community in here looks like one of the best place on the internet.
One of the posts helped me repair a monitor, so thank you for that.
Now I'm having other problems with the same monitor so I'd need some help with it.
Hopefully I'll get to know more in time and will also be able to help others as well.Leave a comment:
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