Measure the caps and determine if they need to be replaced.
On my IRS Beta ALL Solen caps were totally off spec or totally dead. All TI and Wonder caps measured perfectly.
I replaced with new Solen to maintain a level of originality. LEMIMs and EMIMs came to life.
Big change that I had not immediately noticed due to the gradual deterioration of the capacitors (and of my ears).
Back to normal now and fantastic