15W combo with all that DSP type stuff.
Marked RoHS inside , presumably classic PbF problem.
Will break into bad crackle intermittently, so far not with me. Any
known problem area to look at eg speaker, before attacking with the big
guns, hot air, nylon tipped engraving tool, freezer spray ...
Input socket seems ok, no bypass contacts to be problematic

To save graunching the film ribbon, with sub-boards flopping around on
the bench. This amp will give the analogue output,vol and tone change,
without the display pcb connected, but with "computer hash"
superimposed, but the SD/USB pcb needs to be connected via its sloppy
connectors.
At the input TL072 there are 2 SMD diodes D5 and D8 marked JV something,
measuring forward .25V in circuit.
With some low level heating , in that area from hot air, part of the
analogue signal drops out. Resoldering those 2D and 4 nearby R, plus the
traditional usual suspects, including the speaker (initially showed
suspect VC tail/pigtail internal PbF problem perhaps) hopefully has
trapped the problem