Denon PMA 255UK Repair (With Audio Tutorial)

Fault
Intermittent loss of Audio
This issue is common with all Amplifiers that have a relay speaker protection circuit and mechanical input selection.
Switching contact become oxidised and resistive over time.
Speaker protection relay replaced 24 V DC Coil DP/ST
Input selection switch removed from the circuit board taken apart and cleaned with a fibre glass pencil to remove oxidisation.
Volume control potentiometer cleaned with De-Oxit D5 to ensure noise free operation.
Bias for each channel set to 10 millivolts.
Amplifier fully tested working correctly.

[@The_Penguin_Overlord]

old gold lives to fight another day 😃
i am still using a pma 250 mk3 because i just love its old school design and engineering, hell it aint even got standby mode 😄

[@briang.7206]

What are your recommendations for cleaning speaker relays ?

[@AudioAmplifierServicing]

Hi you need to use a contact cleaner and a fiber glass pencil to clean the switching contacts.
www.amazon.co.uk/Modelcraft-PBU1019-1-Glass-Pencil/dp/B002Z8IX36/ref=asc_df_B002Z8IX36/?tag=googshopuk-21&linkCode=df0&hvadid=696285193871&hvpos=&hvnetw=g&hvrand=12870113254195791277&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1007249&hvtargid=pla-2281435177858&psc=1&mcid=edaceba400a5399f923d3f31bda8d947&hvocijid=12870113254195791277-B002Z8IX36-&hvexpln=74&gad_source=1
Do not use any abrasive for example sand paper or a file.
If the oxidisation is ver bad the the relay will need to be replaced.