[sebhc] IC information

William Wilkinson billwilkinson at mindspring.com
Sun Feb 27 17:17:35 CST 2005


Glyn,

I just happen to have the data sheet.  According to it, the extra lead on
the 79MG is a control lead that determines the output voltage.  On the H8,
R233 and R234 sets it to -5VDC.  Quiescent current at 25 degrees C is
typically 0.5 mA (2.5 mA max).  Peak output current is 650 mA.  The 7905 is
about 1 mA (2 mA max) quiescent with a peak output of 2.1 amps.

If you wanted to hack the hardware, you could probably sub it with the 7905.

Looking at the H8 schematic and circuit board x-ray views, the only chips
it appears to feed is the CPU at pin 11 and the ROM (IC-204) at pin 21
through a jumper, T1-T2.  The latter was probably to accommodate various
types of ROMs and EPROMs.

Regards,
Bill


> [Original Message]
> From: Glyn Firth <glynf1 at cox.net>
> To: <sebhc at sebhc.org>
> Date: 2/27/2005 3:23:52 PM
> Subject: Re: [sebhc] IC information
>
> Thanks for the information, I checked on the 7905 and it is a three lead 
> device, the 79MGT2C is  a 4 pin IC on the cpu board. I don't have data 
> sheets on these devices, is there a trick?
> Thanks
> Glyn
> ----- Original Message ----- 
> From: "Barry Watzman" <Watzman at neo.rr.com>
> To: <sebhc at sebhc.org>
> Sent: Sunday, February 27, 2005 2:57 PM
> Subject: RE: [sebhc] IC information
>
>
> > 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.  Online
> > sources:
> >
> > www.jameco.com
> > www.jdr.com
> > www.digikey.com
> > www.meci.com
> >
> > [there are many others]
> >
> > These don't fail often, and they usually fail "open", which might not 
> > screw
> > up the 8080.  Look for another problem.
> >
> >
> >
> > -----Original Message-----
> > From: sebhc-bounces at sebhc.org [mailto:sebhc-bounces at sebhc.org] On
Behalf 
> > Of
> > Glyn Firth
> > Sent: Sunday, February 27, 2005 3:40 PM
> > To: sebhc at sebhc.org
> > Subject: [sebhc] IC information
> >
> > I have just began to rejuvenate my H8 system. I have discovered that the
> > -5volt voltage regulator on the CPU board is bad( I assume the 8080A is 
> > also
> > cooked) The part # is 79MGT2C. I have checked some places on the net and
> > found the IC, but most have a min order of a $100 or so.Does anyone
know 
> > of
> > a source for this IC?
> > Thanks
> > Glyn
> >
> >
> > --
> > Delivered by the SEBHC Mailing List
> > 
>
>
> --
> Delivered by the SEBHC Mailing List



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