+ mental
As someone said Sansui did use glue on the boards but I think he has over stated the issues. Sansui integrated's are going up fast in the vintage market for a reason if you can get one like the 717 i'd jump on it they are only going up in price. Also Luxman, Accuphase older stuff are some of the best made form that era worth looking as well. but may be to late to get for under $500.
As someone said Sansui did use glue on the boards but I think he has over stated the issues. Sansui integrated's are going up fast in the vintage market for a reason if you can get one like the 717 i'd jump on it they are only going up in price. Also Luxman, Accuphase older stuff are some of the best made form that era worth looking as well. but may be to late to get for under $500.