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My Apple //e repair - No boot

Hello Clint,

at this point just some infos and a reminder....
the images of the ROMs are downloadable from:
http://mirrors.apple2.org.za/Apple .../Computers/Apple II/Apple II plus/ROM Images/
the Eprom should be a 2716
please avoid the use of a 27C16....
If you replace ROM with Eprom be aware that the EPROM has slight other behaviour and a small modification is demanded:
http://www.appleii-box.de/H019_ROMtauschGG2716imAppleIIP1.htm

like explaines in the previous posting it might be recommended to replace socket....
before you make such attempt i'd recommend to reread this page:
http://www.appleii-box.de/D05_basicsoldering.htm
and probably it's a good idea to repeat the exercises proposed there....

sincerely
speedyG
 
Clint said:
Well today I cleaned up every IC and reseated, I also replaced all the RAM with new.

I also noticed that C2 Was running very hot:

So anyone got any ideas, I dont have replacement IC's here so need to order some, but pleased I can see an issue :)
Click to expand...

I fired up a board here with C2 removed and it has the same no video symptom you are getting.
So there is a good chance that C2 is faulty as you suspect.
 
My Chips arrived today, I replaced C2 74S195 but still no 1Mhz, but I did have 2Mhz and then checked the output of B1, replaced B1 74S175 and immediately presented with a beep at power on.

IMG_1539.jpg

Also C2 is no longer hot !

Next job is to attach keyboard and a monitor to see what we have.

One step forward :)
 
Before I go any further I just wanted to check something.

This Apple came with an 80 column card with extra RAM, I took this card out, apart from putting the missing DRAM chip back on the system board was there anything else I need to change back ?

The screen does flicker when turned on but no display at all.

Here is a picture of my complete board.

IMG_1545.jpg
 
No, that's all you have to do.

Are you getting a clean raster?

You do get a beep when turning on, which is a really good start. I wonder if that happens if you force a reset signal at the microprocessor. Also, it may be worthwhile to probe the /RESET line with you press RESET, or CTRL+RESET.

Another thing to try, is press CTRL+G and see if you get a beep.
 
Hi Clint
You might want to do something like the debug board I'm building for the KIM-1.
The idea is to have a ROM that you have your own code in to exercise some specific
part of the Apple board.
If you not into designing your own, you might consider the SwyftCard replica that
Mike has created See:

http://www.willegal.net/appleii/appleii-first_page.htm

At $55 it would be a bargain. You can create code for your own EPROMs and
then run tight diagnostic loops on the Apple.
It only requires a minimal amount of circuits working on the Apple board.
When you finally get your Apple up and running, You'll have the cool
SwyftCard to play with.
I'd recommend making a simple adapter between the EPROM and the board with
some address switches to be able to select smaller pieces of the EPROM.
That way, you could have more separate diagnostic codes at different addresses
of the EPROM.
Dwight
 
I have a ROMable simple RAM test that I wrote that doesn't need
any working RAM while running. I wrote it for the KIM-1 debug board.
It needs some method of display of status. I used a LED on my board
but on the Apple board, I don't know if there is a LED on a port.
If not, most any addressed location could be monitored with a 'scope.
Getting working zero page RAM is a must to do any other testing of
the rest of RAM or I/O operations.
The 6502 doesn't like to run without zero page and stack.
I use every register and the stack point for temporary storage.
Dwight
 
No LED on the Apple ][ (there is on the //e, just for this purpose), but there is a speaker, where, for diagnostic purposes, an LED could be substituted (just like on the //e).
 
If you get the beep then its basically working rom/ram is all good reset is also working.

Just check the trimmer near the video connector, its the brightness control and sometimes they are turned down.
On the right hand side of the board, row J. there are three resistors and a transistor. That is the video mixing, colour burst, video and sync. You should activity on both video and sync but not colour burst.
Sometimes the transistor dies but most often its just the trimmer turned down or a bad video cable.
 
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