The 5amp TO3 packaged 5V regulators ( LM78H05K or UA78H05 ) are used on a lot of pinball power supply boards but have been obsolete for some time and NOS units are typically around £20 each if you can find them. I recently bought some on ebay from a Chinese seller at a price that seemed too good to be true - and it was! I fitted one to a board and thought it best to load it up before connecting it to a machine. It measured fine off load and up to about 1amp before dying. The reason is obvious when I cut it open and compared it with a (dead) real one.
The one on the left is a genuine 5amp device which is fabricated from a controller chip with an external power transistor. The one on the right is the Chinese fake which has about 5% of the chip area of the real one and tiny bonding wires that have fused at about 1amp. I think the large blue glass insulators may be an easy way to spot a fake as they don't leave enough area in the package for the correct size of die. The genuine one also has a thicker base where the die sits and this is visible on the underside of the package.
I have ordered some of these high efficiency 5A switched-mode replacement devices and will update this post when I have had chance to test them, but they have to come from the States:
https://www.ezsbc.com/index.php/featured-products-list-home-page/psu7.html#.XPKkPv57mUk
Their 3amp devices have had good reviews so I am hopeful that these will make a reliable replacement.
The one on the left is a genuine 5amp device which is fabricated from a controller chip with an external power transistor. The one on the right is the Chinese fake which has about 5% of the chip area of the real one and tiny bonding wires that have fused at about 1amp. I think the large blue glass insulators may be an easy way to spot a fake as they don't leave enough area in the package for the correct size of die. The genuine one also has a thicker base where the die sits and this is visible on the underside of the package.
I have ordered some of these high efficiency 5A switched-mode replacement devices and will update this post when I have had chance to test them, but they have to come from the States:
https://www.ezsbc.com/index.php/featured-products-list-home-page/psu7.html#.XPKkPv57mUk
Their 3amp devices have had good reviews so I am hopeful that these will make a reliable replacement.
