Relay buzzing after transformer change?

[BabuBinks]

Ideal 4180 Paper Gulilotine stopped working. Changed fuse in the 230v > 24v transformer. A relay started buzzing on the PCB upstream. Thought it was a damaged relay so I replaced it for like.

Tested output on transformer and was only outputting 8v. Replaced the transformer for like also. Output is 31v and relay still buzzing.

What I'm confused about is that the relays on the PCB are DC but the old transformer and new transformer both output AC, how did the old transformer work as it was manufactured like this? There is nothing between the transformer and PCB to change the current.

The PCB is rectangular with a relay on either side with 3 capacitors in the middle. Between the relays and the edge of the board there are two diodes on each side.

Images below are the old Transformer next to the new transformer and the PCB

Any help would be appreciated.

 

[Diver300]

I can't be absolutely sure without measurements, but it will be the capacitors. Those are electrolytic capacitors and their capacitance reduces and their ESR (equivalent series resistance) increases with age. The relay is 24 V DC, so the coil is run from a rectifier, and the capacitors are there to smooth the supply. Without a smoothed supply, the coil current will dip a lot every mains cycle and lead to buzzing.

Relays contacts can wear out but the coil doesn't. The coil is DC, and a relay with a steady DC current will never buzz.

Transformers last for ever unless they get overheated.