Power Supply Replace

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By tvalenca

Paladin (747)

Аватар пользователя tvalenca

07-09-2016, 17:48

maxis wrote:
tvalenca wrote:

I think our folks Maxis, Alexey and Retrotechie would be interested on more detailed pics from its board.

I'm very interested indeed. Simply never seen anything like that in western computers Wink

I'm just horrified thinking that a computer manufacturer used just a 7805 to get 1.5A!

By Wierzbowsky

Guardian (3648)

Аватар пользователя Wierzbowsky

07-09-2016, 17:52

Some actually did. Sinclairs used 7805 on a very power hungry board. As a result they had to put a big heatsink in a small case (zx81 is an example).

By RetroTechie

Paragon (1563)

Аватар пользователя RetroTechie

07-09-2016, 23:42

The humble mighty 7805 is a decent regulator, IF cooled properly AND not supplied with reverse polarity on its input OR input shorted with voltage on the output. Too small cooling blocks makes it run hot, which reduces lifespan (like in those Sinclair machines mentioned above).

Treated properly, it is robust, does its job well, is easy to find, cheap, and for many many applications good enough. Even though there are also many many better parts out there (almost as cheap or cheaper). Not to mention that any electronics people will know the 78xx from head... :-)

(FYI: there aren't that many electronic IC's that have their own Wikipedia article, never mind a full page. The 78xx is about as famous as the 555 timer or 741 opamp)

By marcoexo

Expert (83)

Аватар пользователя marcoexo

28-01-2018, 23:13

Hi all, I'm trying to repair this same power supply from a Fenner MSX1, It looks like no schematic is available on the net, but it should be an easy task anyway... I'm missing +5v (and yes, I did short the slot switch ;-) ).
I found a broken power output transistor, but cannot find the spec for an equivalent.. Labeled GS H 2053 .. anybody can suggest a replacement ?
Looks like being an PNP I think so, since I have +23v on it's emitter

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