Path: utzoo!attcan!uunet!cbmvax!fred
From: fred@cbmvax.UUCP (Fred Bowen)
Newsgroups: comp.sys.cbm
Subject: Re: Homemade Power Supply (was: Ambitious RAM Expansion Hacking)
Message-ID: <5781@cbmvax.UUCP>
Date: 25 Jan 89 17:03:16 GMT
References: <1287.23DA03C5@isishq.FIDONET.ORG> <531@csd4.milw.wisc.edu> <145@oodis01.ARPA>
Reply-To: fred@cbmvax.UUCP (Fred Bowen)
Organization: Commodore Technology, West Chester, PA
Lines: 37

In article <145@oodis01.ARPA> figueroa@oodis01.ARPA (Andrew Figueroa) writes:
>I built a C-64 P/S from a "Power-One" HB5-3/OVP-A 3 amp DC power supply (this
>is regulated with overvoltage protection).     [...]
>I needed a 9V 1 Amp transformer to complete the project but only found a 9V .5
>Amp transformer to complete the kit.  My review of the C-64 schematics and
>references in the C-64 Programmers Reference Guide led me to believe that .5
>Amp is enough.

The "beefier" supply that comes with the 1764 expander is 4.3A@5V and 1A@9V,
designed around the assumption something is sucking power from user, cassette,
and expansion ports.  For example, the 1750 peaks out at around 500mA, and a
BusCard plus 80 column adaptor will certainly draw over 500mA.  A 1670 modem
takes about 50mA, and a datasette requires 5V 150mA as well as 9V 500mA.

An analysis of 5V requirements depends upon the vintage C64 you have, but even
the more recent short boards (say 1.5A max) plus a RAM expander (.5A) combine
for a 3A minimum recommendation.

An analysis of 9V requirements shows SID (50mA) plus datasette (500mA), hence
the 1A recommendation.

>(disclaimer - "Kids, don't try this at home.  You may burn yourself with the
>soldering iron, burn the house down, or destroy your computer, yourself, or a
>friend."  I don't know how these things work - I just put them together!)

Good advice.

>Andy Figueroa
>aka "figueroa@wpdis01.arpa"

--
-- 
Fred Bowen			uucp:	{uunet|rutgers|pyramid}!cbmvax!fred
				arpa:	cbmvax!fred@uunet.uu.net
				tele:	215 431-9100

Commodore Electronics, Ltd.,  1200 Wilson Drive,  West Chester,  PA,  19380