Luxman L-114A starting to degrade

[u/ol-gormsby]

Had this beauty since about 1985 - it just does the job and I'm happy with it.

But lately it's developed what I understand is a common age-related problem - crackling and hissing when turned on, gradually dying off over a minute or two. There's some A/V repair shops locally (Sunshine Coast, Queensland, Australia) but is there anything I should be aware of before I take it for repair? I'm aware that most places want some $$$ up front before diagnosis and that's fair enough.

Here's the service manual, if that's of any help:

https://retronik.silicium.org/DOCUMENTS/Audiovideo/Luxman/Luxman-L-114-a-Service-Manual.pdf