LNK304 Output pulsing

Posted by: diogoc on 06/17/2024

I'm replacing a blown LNK304 in a washing machine.

After replacing this component plus the 33ohm fusible resistor, I found that the output voltage is pulsing at aprox 500ms.

Tested all the components in the power suply and all are ok.

Mounted an external board with the same schematic as in the datasheet and still the same.

Buyed more LNK304 from multiple suppliers and all of them have the same behaviour, except one.

The pieces from this supplier worked perfectly.

Looking at them the only difference is the logo. The working ones have printed the old logo and the parts not working have the new logo.

There is a new revision of this part that have something different inside?

Do you think can be fake parts? It is very strange multiple supliers have all fake parts.

Thanks

Comments

Hi,

In order for us to investigate this issue further, I would like to request for the schematic design, magnetics design and PI Expert (if available) of the PSU. This is for me to check if there is a marginal parameter that causes this response to other suppliers' ICs. Different batches of IC might have differences in tolerances, and we want to make sure that your design will behave the same regardless of batch of IC.

Also, I would also like to suggest using LinkSwitch-TN2, a newer version of the IC you are using.

I will wait for your response.

Have a great day ahead!

Kind regards,

PI-Zoe

Hi,

This is not my design, it was from a washing machine that I'm repairing and worked more than 5 years.
The manufacturer of the board is VesteI and don't think they released a board that is dependent of the IC tolerances.

Attached you have the schematic from reverse enginnering the board.

Regarding your suggestion of LinkSwitch-TN2, there is any part that can be used as a direct replacement of the LNK304?

Thanks

Diogo

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Hi Diogo,

Thank you for your response.

We reviewed the design you provided and found no issue with it. Since the design worked for a long time the quality of the newer ICs might be the problem.

For concerns regarding quality, please fill out the form below. Please include the supplier on the Request Content part of the form.

CIM Request for Integrated Circuits only (smartsheet.com)

Unfortunately, there is no direct replacement IC that can be used in place of LinkSwitch-TN in terms of pin configuration. Using LinkSwitch-TN2 will require a re-layout since they do not have the same pin configuration.

I am hoping that this helps.

Kind regards,

PI-Zoe