Re: Misbehaving Apple II+ -- Help!

[Michael J. Mahon <mjmahon@aol.com>]

"Apple2Steward" <none@none.net> wrote:
> I left my Apple II+ running for a day with the clock 
> (Thunderclock) program running, and when I went to check on it 
> there was a smell like hot electronics and garbage on the screen.
> 
> I shut it off for an hour and with a restart I got the power on 
> light, and a noise from the speaker (but no real beep), no disk 
> drive spinning and nothing on the screen. Same with all cards 
> removed.
> 
> I checked the power supply voltages at the connector (no load) 
> and got 20 and 8 volts.
> 
> I had a spare good power supply and swapped it in, and now get 
> the power on light, no beep, and a screen filled with alternating 
> horizontal bars and rows of question marks.
> 
> I disassembled the computer and inspected the board but don't see 
> anything obviously burned or swollen.
> 
> My troubleshooting manual equates this situation with either a 
> bad 6502, or bad F8 ROM.
> 
> I don't have a spare F8 ROM, but do have an Apple IIe with a 
> 6502B.
> 
> So my questions are
> 
> 1.  Can I swap in the IIe CPU to test?
> 2.  Are there other likely sources of failure?
> 3.  Are new 6502s available if that's the problem?
> 
> Suggestions would be most appreciated!

Ouch!

+5v going to 8v and +12v to 20v does not bode well for your main board or
your cards. 

I'm afraid they may be too damaged to make repair practical--though it
never hurts to try. 

Most diagnostic guides are based on the assumption of a single failure, and
that seems optimistic in your case. 

-michael  -  NadaNet 3.1:  http://home.comcast.net/~mjmahon