Re: Apple IIpluse motherboard problem

[Patrick Schaefer <PSchaefer@epost.de>]

Vince Briel schrieb:
> 
> Hi, I have an extra ][plus motherboard that when powered up, just gives
> scrambled text on the screen.  I have swapped out all of the chips with

Do you get a beep from the speaker? This indicates your 6502 is running.
Main oscillator and Timing seems to be okay, otherwise you won't get any
letters on the screen.

I fno beep: Connect a keyboard and press RESET (or Ctrl-Reset). Use a
voltmeter or bicyle lamp to check the voltage on the /RESET line. It
should go low immediately after power-on or when RESET is pressed, and
high a few miliseconds afterwards. If not, one of the 555s or its
inverter transistor is dead. Or the electrolytic cap connected to it.


Patrick