Just got my first Apple IIGS, won't boot though.

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Joined: Nov 1 2015
Posts: 7

I went to an estate sale recently and found an Apple IIGS. I was very intrigued since I had never before gotten a chance to get my hands on an older piece of computer history.

Unfortunately I have not been able to get it to boot up. The computer turns on, floppy drives flash a light once, the keyboard flashes all three lights once, but I never get a sound from the speaker and the monitor only displays a green screen with four black squares.
Here's a link to what the monitor shows

I've done some basic troubleshooting including testing the power supply for the correct voltages.
The only thing I found that seems strange are 2 cuts on the motherboard traces.
The first cut is on the top of the GLU Here.
The second cut is on the back, as well as a wire jumper and a capacitor and resistor jumper. Here

Does anyone have any experience with this kind of thing? I would really love to get this thing working again!

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Joined: Dec 20 2008
Posts: 211
Re: Just got my first Apple IIGS, won't boot though.

Could be a lot of different things...

First thing to check for is battery damage. Is there any under the power supply?

Second thing to check is power supply voltages. Make sure they are all in specification.

Also, make sure there is a ROM in there (no empty sockets in general) and that the pins are not bent.

I wouldn't worry about that mod for now, it's not likely causing the underlying issue.

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Peter Rittwage
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Joined: Nov 1 2015
Posts: 7
Re: Just got my first Apple IIGS, won't boot though.

Thanks for your reply!

I went ahead and closely examined for battery damage, but there appears to be none.

Power supply voltages are the correct voltages on the correct pins.

The ROM is in the correct socket and except for the white plastic socket that says game there aren't any missing.
I can't see any bent pins on any ICs and I'm pretty stumped as to where to proceed.

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Joined: Dec 20 2008
Posts: 211
Re: Just got my first Apple IIGS, won't boot though.

Well, unfortunately you are not lucky and it's not an easy fix, then. Perhaps someone will chime in with more experience with the IIgs. It's definitely the most difficult ][ to troubleshoot, as most functionality was integrated into VLSI. You could try to verify that the ROM is good, or the RAM is good, but beyond that it would require a good scope and advanced electronic skills and experience. If you lack that, it may be one to put on the shelf and use for parts - or buy a known good motherboard to swap.

You have all cards removed, including RAM card?

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Peter Rittwage
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Joined: Nov 1 2015
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Re: Just got my first Apple IIGS, won't boot though.

I have cards removed right now including the RAM card.
It seems as though we're out of ideas until someone with more experience steps in.
I really appreciate your help!

ggb
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Joined: Mar 13 2012
Posts: 31
Re: Just got my first Apple IIGS, won't boot though.

What tools and electronic experience do you have.
Just confirming this is your first IIgs.

GeoffB

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Joined: Jun 8 2004
Posts: 1
Re: Just got my first Apple IIGS, won't boot though.

If you still have this IIgs that won't work properly, come on over to Facebook and the Apple II Enthusiast page and there are a ton of high-tech Apple II types that can help.

Charles Lott

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Joined: Nov 1 2015
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Re: Just got my first Apple IIGS, won't boot though.

I have an oscilloscope and intermediate level experience with electronics.
This is the very first Apple I've owned.

ggb
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Joined: Mar 13 2012
Posts: 31
Re: Just got my first Apple IIGS, won't boot though.

If you get the data sheet for 65816 you can start by checking if the reset pin 40 on the cpu is being held low or high, high state the cpu will run code.
Then check PHI2 pin 37 on the cpu for 2.8MHz clock

geoffB

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Joined: Nov 1 2015
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Re: Just got my first Apple IIGS, won't boot though.

I followed your instructions and found that the reset pin on the CPU is getting a continuous 5V.
When I hit Ctrl, Open Apple, Reset the voltage drops and then rises back to 5V quickly.

But when I checked pin 37 on the CPU for 2.8MHz clock, I only measured 1.02MHz.

ggb
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Joined: Mar 13 2012
Posts: 31
Re: Just got my first Apple IIGS, won't boot though.

thinking about the way the speed is controlled, starting at 1MHz makes sense as the control registers are probably cleared on powerup.
A schematic of the IIgs ROM01 can be found at the link below.
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Computers/Apple%20II/Apple%20IIGS/Schematics/Apple%20IIGS%20ROM%2001%20Schematics.pdf

Check the CS pin 20 of the ROM chip pulses low for access, should start occurring after Reset goes high.

GeoffB

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Joined: Nov 1 2015
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Re: Just got my first Apple IIGS, won't boot though.

I checked pin 20 of the ROM chip and it does pulse low after reset, it comes to rest at 2.5V

I really appreciate your help!
hopefully we can figure out what's wrong.

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Joined: Oct 22 2011
Posts: 8
Re: Just got my first Apple IIGS, won't boot though.

Crash

Power up your IIGS holding down the "Open Apple" and "Closed Apple" keys.

Your computer should run a self diagnostics test. What did it tell you?

060660

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Joined: Nov 1 2015
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Re: Just got my first Apple IIGS, won't boot though.

When I do that I don't get any indication that the computer has done anything. The screen shows the same thing and there's no speaker or drive noise.

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Joined: Dec 20 2008
Posts: 211
Re: Just got my first Apple IIGS, won't boot though.

Seems like it's not getting far enough in the boot process to run any ROM code, or else the ROM is bad... More likely the former.

I know... not very helpful. However the IIgs is full of mostly custom chips, so not much you can from "10000 feet".

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Peter Rittwage
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Joined: Jun 22 2012
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Re: Just got my first Apple IIGS, won't boot though.

You should post a picture of the clock signal on pin 37.
Your 'scope should be using a 10x probe, otherwise you will load down the clock signal.
Replacement MB's are $25.00 and up on ebay, look for a ROM 3 unless you are trying to keep it original.
You could then possibly troubleshoot you orig. MB by swapping the CPU or VGC ic's.
Anything else requires soldering. Not worth too much of your time, unless you're just trying to learn more.
Good Luck!