[sebhc] IC information

[Glyn Firth]

Lee,
     I do not have the schematic, would you please advise.
Thanks
Glyn
--- Original Message ----- 
From: "Lee Hart" <leeahart at earthlink.net>
To: <sebhc at sebhc.org>
Sent: Sunday, February 27, 2005 7:26 PM
Subject: Re: [sebhc] IC information


> Glyn Firth wrote:
>>> I have just began to rejuvenate my H8 system. I have discovered
>>> that the -5volt voltage regulator on the CPU board is bad...
>>> The part # is 79MGT2C.
> 
> Barry Watzman wrote:
>> You can probably get one at Radio Shack, it's just a 7905, in an
>> appropriate case (probably TO-220, but 7905's come in lots of
>> different case styles, the letters don't matter). Very, very
>> common and inexpensive part.
> 
> No, Glyn is right. The H8 8080 CPU board uses a *very* unusual part,
> nothing like a generic 7905. The 79MGT2C (Heath 442-618) looks like an
> 8-pin DIP, but with pins 2,3,6,7 replaced by large wide "bat wing" ears.
> It is actually a -2.25v regulator, and uses two external resistors to
> program the output voltage to -5v.
> 
> Finding an exact replacement *will* be a challenge! However, if you just
> want to get the H8 functional, I would replace it with a 7905 (or
> equivalent 3-terminal regulator.
> 
> This is pretty straightforward if you have the schematic. If you need
> instructions to do this, ask.
> -- 
> "Never doubt that the work of a small group of thoughtful, committed
> citizens can change the world. Indeed, it's the only thing that ever
> has!" -- Margaret Mead
> --
> Lee A. Hart  814 8th Ave N  Sartell MN 56377  leeahart_at_earthlink.net
> 
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