Can anyone suggest a cheaper part no. Against fsdmo465r??

 

Need substitute for what?
Put it in the title.

 

It is obvious that the original markings have deliberately been removed so that part number must be used. . Probably it is a commonly available component, most likely an amplifier. If we are given the application circuit probably a replacement type can be determined. It may be something like a TDA 2005, as an example.

 

Need substitute for what?
Put it in the title.

Part no. Fsdmo465r

 

The photo shows a 5-lead T0-220 PLASTIC PACKAGE with the original markings very deliberately removed. That part number is a manufacturers assigned number designed to hide the actual identity of the component.
IF we can get a description of the equipment that it was part of, and possibly a bit of the associated circuit, it will be possible to suggest an alternative.

 

It is obvious that the original markings have deliberately been removed so that part number must be used. . Probably it is a commonly available component, most likely an amplifier. If we are given the application circuit probably a replacement type can be determined. It may be something like a TDA 2005, as an example.

Used in a simple 48w power supply to run a motor

 

OK, it is used in a 48volt system to run a motor. Is there a way to show us any portion of the circuit, at least the power supply and motor connections to the IC? And any motor ratings, like voltage and current? That will be useful in determining what the device is.

 

Is it a Fairchild (now On-Semi) off-line switched-mode regulator?
https://www.onsemi.com/products/pow...llers-regulators/offline-regulators/fsgm0465r
https://www.onsemi.com/products/pow...llers-regulators/offline-regulators/fsq0465rs

 

Is it a Fairchild (now On-Semi) off-line switched-mode regulator?
https://www.onsemi.com/products/pow...llers-regulators/offline-regulators/fsgm0465r
https://www.onsemi.com/products/pow...llers-regulators/offline-regulators/fsq0465rs

We don't know if it is a servo amplifier supply or what. Thus we are guessing until more information is provided.

 

We don't know if it is a servo amplifier supply or what. Thus we are guessing until more information is provided.

getting closer. . .
https://www.mouser.com/datasheet/2/308/fsdm0465rs-1192317.pdf
£1.38 each from Mouser for 1 off, and that doesn't seem like an unreasonable price to me, for a 50W switched-mode controller with built-in MOSFET.
[EDIT] $0.83 each on On Semi's website for 1000 off, but NRND.