Toshiba Satellite S300CDS PSU failure

[Jules]

The little PSU brick for my old Toshiba Satellite S300CDS laptop just
decided to keel over - no DC output whatsoever. (should output 15V)

Has anyone any experience of these and know of any common failures?

Checked the usual stuff - fuse is ok, bridge is ok, chopper transistor
appears good on a meter etc.

I'm getting nothing on the low voltage side of things though, suggesting
that there's no drive to the chopper. Unfortunatley there's a tiny
surface-mount IC in there which is probably impossible to get, plus a
hybrid circuit on the output side which would be even more impossible to
obtain

cheers

Jules

 

[Jerry G.]

These are not supported for service at the component level. Toshiba sells
the complete unit as a module. It is very common that the capacitors, and
the pulse chopper/generator IC fails in these. There are no internal parts
support from Toshiba.

You have three options, if it is not a simple fault. You can either order a
new power unit from Toshiba, or design and build your own, or you can call
around to the various electronics parts suppliers and see if they can sell
you a regulated 15 Volt / 5 Amp rated supply.

Before doing any experimenting make sure that you are very sure of the
proper specifications require for the computer. Make sure you never reverse
the polarity of the supply, or the mother board will be instantly damaged.

--

Jerry G.
======



The little PSU brick for my old Toshiba Satellite S300CDS laptop just
decided to keel over - no DC output whatsoever. (should output 15V)

Has anyone any experience of these and know of any common failures?

Checked the usual stuff - fuse is ok, bridge is ok, chopper transistor
appears good on a meter etc.

I'm getting nothing on the low voltage side of things though, suggesting
that there's no drive to the chopper. Unfortunatley there's a tiny
surface-mount IC in there which is probably impossible to get, plus a
hybrid circuit on the output side which would be even more impossible to
obtain

cheers

Jules

 

[Franc Zabkar]

The little PSU brick for my old Toshiba Satellite S300CDS laptop just
decided to keel over - no DC output whatsoever. (should output 15V)

Has anyone any experience of these and know of any common failures?

Checked the usual stuff - fuse is ok, bridge is ok, chopper transistor
appears good on a meter etc.

I'm getting nothing on the low voltage side of things though, suggesting
that there's no drive to the chopper. Unfortunatley there's a tiny
surface-mount IC in there which is probably impossible to get, plus a
hybrid circuit on the output side which would be even more impossible to
obtain

The "no drive" condition in a SMPS is often due to an open resistor
(~100K - 200K) in the base/gate drive to the chopper transistor. If
this is the case, then the voltage on the main filter cap will be
around 340VDC even after removing power from the circuit.


- Franc Zabkar