RE: Static PET PSU questions - oops

Oops; CR2 had disappeared somehow...
And I probably should have used a fixed pitch font...

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From: 	M H Stein[SMTP:dm561@torfree.net]
Sent: 	Wednesday, September 30, 2009 7:56 PM
To: 	'cbm-hackers@ling.gu.se'
Cc: 	'ethan.dicks@gmail.com'
Subject: 	RE: Static PET PSU questions

Pretty straightforward:

pins 1 and 5 are the ends of a center-tapped secondary,
pin 3 is the center tap and Cap -
pins 2 and 4 are DC returning from the board and connected together at 
the Cap +

The 320008-2 schematic is correct for the board.

If you've got ~9V DC available, just feed 9VDC to pins 2 and 3.

If you're going to use a PC-type PS, I'd pull the regulators (if they're not 
still out) and run regulated 5V to the 4 Vcc points and drop the 12V
to ~9 with a regulator or Zener and connect to pin 2.

But I accept no liability ;-)

X----------------- 1 ----->|------+
X                         CR1     |
X                                 |
X                                 |
X    +-----+------ 2 -------------+-----+----------------> 9V DC to regulators and Cass drivers
X    |    _|_                          _|_
X    |    _ _  C  23000/15             /_\  CR3
X    |     |                            |   
X----------+------ 3 -------------------+----------------> GND
X    |
X    |
X    |
x    +-----------  4 -------------+                   
X                                 |
X                                 |
X                         CR2     |
X----------------- 5 ----->|------+


mike

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From: 	Ethan Dicks[SMTP:ethan.dicks@gmail.com]
Sent: 	Wednesday, September 30, 2009 5:34 PM
To: 	cbm-hackers
Subject: 	Static PET PSU questions

Hi, All,

Back on that 2001-8 board... it's a P/N 320008, original board.  It
has a 5-pin power supply connector.  From the schematics, pin 3 is
GND, pin 2 is unreg 9VDC, and there's a pair of half-wave diodes from
pins 1 and 5 to pin 4.  I want to run this board in a more modern PET
chassis (so far I've been using external +5VDC through TP1 down by the
internal cassette port).  I've never been able to locate a
chassis-specific schematic of any PET to match up the rectifiers and
regulators on the board with the transformer and filter cap in the
chassis.  Can anyone point me to such a document on zimmers.net or
anywhere else?  I have the general idea of what needs to happen, but
I'd rather not fry my only #320008 board trying to put it someplace
"interesting" because I failed to understand some important detail.

Thanks,

-ethan

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