Teenage Mutant ninja Turtles 1980s arcade game with CRT (sound problem)

[coskydoodle]

I have had this arcade for 30 years or more but stored it in my dry barn for last 10 years. Now its time to move it on as my kids are now  36 and 40 years old.
I am a TV engineer by trade so used a rheostat to bring the mains up from zero in stage of an hour up to 240 volt a/c (we are in Cornwall UK)

Surprisingly everything was fine. Brilliant picture on the CRT and great graphics and it functions fine.
However the sound goes distorted and low volume after just 5 minutes and seems to pulse in time with the flashing coin lights on the front.
So I replaced the +5/-5 +12 power module and carefully set it up but its exactly the same.
Checked all the electrolytic caps with an ESR meter and they seem ok

Tried a can of freezer on most components once the sound distortion stats but no difference

Any help appreciated...just wondering if its the tantalum 4.6uf 16v caps faulty, but they too check out ok on ESR meter.

The audio output of  it is always fine with plenty of clear mains hum if I hold the metal shaft of a small screwdriver and touch the volume control

[coskydoodle]

Guess not many people have had any experiences with TMNT games then?

[JimmyU]

I found this for you. Konami had a lot of problems with their sound boards.
https://www.aussiearcade.com/topic/94407-konami-teenage-mutant-ninja-turtles-sound-issues-fix/