Re: What tells the tube to power up? -- Welcome to the Colo(u)r Classic Forum

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Date Posted: 11:47:26 08/04/01 Sat
Author: Stuart Bell
Subject: Re: What tells the tube to power up?
In reply to: Scott Johnston 's message, "Re: What tells the tube to power up?" on 23:42:30 08/03/01 Fri

At the risk of complicating things in an attempt to simplify them, ;-), perhaps we need to distinguish what tells the tube to power up from what tells the system to power up.

On their own, the CRT plus analogue board assembly will power up as soon as the mains switch on the back of the CC is turned on.

Once a CC has a logic board installed. 'power off' is asserted by S5 on the edgle connector (which goes to pin 7 on the analogue board connector) to tell the CRT/analogue board assembly NOT to be 'on'.

When the keyboard 'on' switch is pressed, 'power off' is de-asserted and the machine starts. As many know, if there is a problem in the boot sequence, 'power-off' may be re-asserted, and the system goes to sleep again.

One consequence of this process is that if you want a twin PSU CC to mimic normal operation, you need some judicious use of relays in the right place.

hth,

Stuart.

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