IR3M02 from Sharp Corporation. Find the PDF Datasheet, Specifications and Distributor Information. IR3M02 Pulse Width Modulation Type Switching Regulator Contrl ic. Details, datasheet, quote on part number: IR3M Electronic component datasheet for IR3M02 manufacturer SHARP. Free doqnload!.

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From what i understand it is not needed usually. Connect DC supply via a current limiting resistor eg ohms to SMPS IC – check voltage on each IC to determine that supply is within range, increase DC voltage until all ICs are powered up, check ir3k02 drop across current limiting resistor for current drain. Good Idea I am going to try to get an early nights sleep to night.

At present my only idea is to disable the auto-shutdown feature of the IR3MO2 and see what happens. Your AC should be plugged into the other connector where the fuse is. That sounds like it’s running correctly, did you get a kick from the datasheft Then check the comparator ICs, ratasheet probably contains two or more comparators, each has two inputs and one output.

With AC i get maybe V. I’m out of ideas but thinking you may be right that the primary of T1 is shorted.

Usually, on a supply of this vintage, there’s a voltage selector switch mounted on the power supply case that selects between and v. Its been a while since I read the values on a power resistor, is the placement of the ohm symbol supposed to indicate the multiplier?


I just enjoy doing this kind of troubleshooting. Here’s dataseet typical example http: If you’ve got a DMM with a capacitance scale, lift one of the legs from the board and verify the value. Ive got a bit of a headache right now so i will investigate it later.

IR3M02 View Datasheet(PDF) – Sharp Electronics

This or3m02 me to believe that, there is something wrong in the output section. Not exhaustive but the best i can do. Here are his 1. I haven’t been exhaustive, partly because its a bit beyond me and partly because it is only an AT PSU.

Sorry to sound vague but this is a bit out of my league.

I have looked over the board and as far as I can tell its fine. I have been looking for a startup resistor but I don’t seem to be able to find one. That’s way too much.

Set up as per Sencore guide would be as follows: A schematic and a scope would be needed to narrow it down further. I get about 7V on the 12V and 3V on the 5V for a second and then it dies. Datwsheet if there is a short on the secondary of T1?

Not sure if connecting this is a good idea, with that Auxiliary PSU powering part of it. Connect J1 and measure AC across the red points.

AT PSU repair [Archive] – Vintage Computer Forum

Because the stuff coming off of the transformer is high-frequency, you don’t need nearly as large a smoothing capacitor than you would if you were dealing with line frequencies.


What is the AC across the blue? The outputs are taken from windings on the transformer, datasehet and filtered. Usually, one output is selected as the reference value for oscillator control. I would still advise trying the caps Paul mentioned 1st.

The fact that the fan spins temporarily then stops indicates the power supply is starting up then shutting down due to a fault. Yes my diagram is wrong, the circuit is correct however. Both cathodes should be pointing to C1, both anodes should be pointing to C2.

IR3M02 (SHARP) – Pulse Width Modulation Type Switching Regulator Contrl Ic, Switching Regulators

Don’t know the history at all. That it’s part of a tank circuit is the reason for the non-polar. So other than dodgy caps, what can go wrong? If they are unequal, that AC might be subtracted across T1. A project a long time ago.

There are 2 ceramic power resistors. What’s the history of this PSU, Has it worked since you’ve had it or did you get it non working, Bleeder resisters adtasheet in parallel with the cap, If fitted that is. DC at red ground on white?

T1 secondary yellow is center tapped white using D5 and D6 as full wave bridge filtered by C11 purple.