Help with Mosfet

[angelothewolf]

Hi folks, im trying to repair this PSU and i cant get this part. do you think this mosfet is replaceable???



http://datasheet.eeworld.com.cn/pdf/...63_CPH6302.pdf

[diydidi]

Stick a normal 3pin through hole fet in there.

[Enzo]

I entered the part number into google and it came back with a a number of places that seem to be selling them.

[angelothewolf]

Stick a normal 3pin through hole fet in there.

alright! that should work? any p channel fet? i dont quite undestand what is that mosfet doing there...

[angelothewolf]

I entered the part number into google and it came back with a a number of places that seem to be selling them.

Yes Enzo, i know where to buy it, but it takes too long... i need to fix this with some hurry

[angelothewolf]

btw is a Microkorg synth, it came with cpu and several psu components burnt. i have already repaired some with the same issue, but this time i dont have the time to order that mosfet. usually this came with CPU and/or DSP chips dead and the 5v reg and this mosfet shorted...

[Jazz P Bass]

alright! that should work? any p channel fet? i dont quite undestand what is that mosfet doing there...

The mosfet is the 'switching element'.
It is driven by IC5.

Read the datasheet for iC5.
Page 19 & 20 cover the mosfet or a pnp transistor parameters.
Then you can make a decision.

S8520_8521_E.pdf

[diydidi]

Almost any p channel in a to220 package will have better specs. See what you have and give it a shot.

[angelothewolf]

The mosfet is the 'switching element'.
It is driven by IC5.

Read the datasheet for iC5.
Page 19 & 20 cover the mosfet or a pnp transistor parameters.
Then you can make a decision.

[ATTACH]33181[/ATTACH]

of course, so i can use a bipolar PNP as well, intresting. thanks!

[angelothewolf]

Almost any p channel in a to220 package will have better specs. See what you have and give it a shot.

gonna try that!

[angelothewolf]

Almost any p channel in a to220 package will have better specs. See what you have and give it a shot.

well i put a 2n5460 there and it work like a charm

[km6xz]

Bucking Regulators are not as critical in component selection for capacitance and rise time as SMPS are. The bucking regulator is an efficient power converter, for increasing current available when down converting, so you can get more current out at a lower voltage than you put in. You can make a bucking circuit out of any inductor, a storage capacitor, a switch and either another switch synced to the first one of just a diode. You can even run many in parallel running at different switching frequencies or have them synchronized to the same clock for two transistors per leg even higher efficiency. You can get up to 93% efficiency.

[angelothewolf]

well i put a 2n5460 there and it work like a charm

it work for some time, then the output go betwen 3.6v to 3.8v, the CPU is not very happy about that... the 2N5460 is the only P channel i got

[km6xz]

The converter is not being controlled then, that is the job of the IC that is controlling the gate of the MOSFet. It samples the output and regulates the duty cycle of the switching transistor. It is possible there is not enough gain using the 2N5460 for the controller to be able to control it.

[angelothewolf]

The converter is not being controlled then, that is the job of the IC that is controlling the gate of the MOSFet. It samples the output and regulates the duty cycle of the switching transistor. It is possible there is not enough gain using the 2N5460 for the controller to be able to control it.

i understand, thanks for the clear explanation. i couldnt find any other p channel around here so im thinking on trying the Bipolar way. As Jazz P Bass said, everything i need to know is on IC5 datassheet, for what i understand i need to calculate Rb and Cb to put a bipolar PNP in there, so now im trying to find something similar to the 2SA1213 wich is a 2A transistor.
Luckily i have a bunch of brand new IC5s, i hope i have not damaged the CPU when i tested with the fet, i think the supply reach the 3.8v for a second or so.

any suggestions???

thanks!