Rockola 477 max very loud hum on power up

[shrimpeater]

Box was working fine and had sit for about a month. 
Now I get this extremely loud hum when I power the box up. 
No dobt it's the map. Everything else works fine with amp disconnected. 
Could it be the ICs in the amp? I saw on youtube a person changed ICs and his amp was repaired.
 I always thought it would be some aged caps. 
Not sure where to go. 
Amp is a 52280

[jukenorman]

There's a load of previous queries on the forum about that particular amp.. But if you want a generalisation - poor solder joints, especially where circuit boards connect together (and I will have said that before, no doubt more than once!). Of course, it may not be that but it's always the first thing I look at when I have a 52280A.

Norman.