Yamaha Receiver HTR-5630 – erratic protection behaviour

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Feb 17, 2021
I'm working on a Yamaha HTR-5630 (other versions are DSP-AX340 and RX-V340) and I have the service manual.

It's an odd fault – when cold, the protection circuitry always cuts in at power up. If I give the 'Func 1' board a push at the top (vertically mounted from the motherboard), the power will stay on. If I let go, it cuts out. However, if I keep doing this, eventually the unit will stay powered on, and if I push the same board around in any direction a while after powering up, the power remains on. Heat-related? Capacitor?

There's a secondary, maybe unrelated fault, in that the left channel is reluctant to stay on, but will come on if the input connectors are wiggled – this is for any of the many inputs. That feels like a common connection, but maybe also related to the power issue as the input connector panel is mechanically connected to the Func 1 board by an edge connector.

Looking at the built-in error reporting, I get: "DC PRT 12% A" when cold and failing to power up. After running for while, it shows: "DC PRT 51% A".

Before I delve too deeply, I thought it worth asking whether this rang any bells here. Any thoughts much appreciated.

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