Need help with restoring Apple II Plus.
Apple II Plus,board p/n 820-0001-04, Non-RFI, Rev. 1 board.
What I have done,Replaced the Power Supply.Removed all cards.Removed 32K of RAM, left 16K installed.
What happens when power is applied,
Keyboard power button light is on, and a single beep from the speaker.There is a brief flicker of video showing characters, waving sync, then the screen goes black.
Pressing reset , gives a beep and a repeat of the video flicker.
Adjusted video level on board, same problem.
Next ?
Can you publish a video ? It seems your Apple II boot in self test mode. Maybe a keyboard/keyboard cable/74LS251 problem
What type of video monitor is used?
(Apple II+ doesn't have any self-test mode)
Beep means CPU, RAM, ROM, and a whole lot more are probably working! Just a video (or monitor) issue. Check RCA jack, monitor (analog CRT would be best), and then video circuits.
This is an Apple II Plus, no self test option.
For video display, connecting to an Flat Screen TV that has a composite video input.
Correction on pressing reset - Just gives a beep, No repeat of the short video flicker.
Other testing
Removed RAM memory from Row C, No beep on power up, still see brief video flicker.
Reinstall another bank of RAM chips in Row C, no change.
Started to reseat chips used by video circuits, no change in video output.
Some flat screen TV's may not like the Apple II video (especially early Rev boards). Since you do briefly see characters, I'd say it's 50/50 that the Apple II is just fine. Wavy sync could be an indication of bad video socket (RCA) or cable. Try twisting or wiggling them. Any chance you have a scope? Or an old VHS machine (you could try running Apple video through that to clean it up).
If the problem is just in the monitor, video connection or incompatible signal, then pressing Ctrl-G with all cards removed would produce a beep.
Here's another test you can try. After the wavy text disappears, unplug the video cable from yout TV. Wait 15 seconds and then plug it back in. If you see the wavy text again (even briefly) that means the computer is still outputting video but it's the monitor that doesn't like it.
You should maybe try increasing the video signal strength. Some LCD monitors will kakk out if the video signal is too low.
The video signal level potentiometer is located at position J-14 on the motherboard.
First, Thanks for the Help with my video issue.
Check RCA jack - checks out OK, good continuity to other video pins on board.
Flat screen TV and Apple II video signalAlready using a VHS machine in the loop.Can only see video flash from Apple II Plus connected to VHS machine line input, and video out from VHS machine connected to video input on Flat screen TV. Tried changing out RCA video cable, not a cable problem.
Pressing Ctrl-G - No beep ( No cards installed )
Try increasing the video signal strength - Have tried adjusting the potentiometer multiple times , never get more then a brief video flash.
I have a scope, got it out, bushing the dust off. It has been a while since using a scope.
Since you are not hearing a beep when you press Ctrl-G, the problem is not in the video signal, or you have more than one issue.
Interesting...
Try holding ctrl-reset while you turn on the computer. Keep holding the keys down and see if you get a screen full of gibberish before letting go of the keys.
While holding ctrl-reset then turning on the computer, and Keep holding the keys down, Yes there is flash screen full of gibberish before letting go of the keys. One beep after the keys are released.
Replay2 wrote:
While holding ctrl-reset then turning on the computer, and Keep holding the keys down, Yes there is flash screen full of gibberish before letting go of the keys. One beep after the keys are released.
Ah. That says a lot. Assuming the gibberish screen looked "fine" and not wavy, I would say the video circuits are working fine. And the fact that it clears the screen and beeps would indicate that some of the F8 ROM routines are working. But the next thing it should do is display APPLE ][ at the top of the screen. And since that does not appear to be happening it could indicate a faulty ROM. The lack of beep after ctrl-G also seems to indicate that the CPU has crashed in a way that prevents it from doing the rest of the power on sequence. If there are any boards in the computer slots they should be removed. If you have a ROM card or other source for a replacement F8 ROM, that would be the next thing to try.
Also, as mentioned, these early boards really have pretty bad and non-standard video output. You really need an old mono or color CRT from the 80's to test it properly.
I had a Rev.1 or Rev.2 board before, and it didn't work correctly with any LCD I had. Even with color TV's, the early color killer circuit was not reliable.
I haven't needed to repair a Apple II series computer as of yet. But I will need to rebuild a IIGS in the near future. I've never even used one before. I got the IIGS and lots of other things for free from someone who didn't want all of the stuff.
Here's a link to a book in PDF format that might help. I didn't look in the book yet.
The Apple II plus/IIe troubleshooting and repair guide
https://welib.st/search?page=1&q=Apple+II+repair
To download, select "SLOW DOWNLOAD" and wait the required time before "DOWNLOAD NOW" appears. After it downloads, you'll see that it has a strange file name. Delete all of the uncessary leading characters (all but the real title) to make it easier to find on your computer.
You can search this site for other Apple diagnostic/repair information as well.
It's a safe site. I've downloaded lots of PDF's, Mobi's, and other format books and documents. All scan clean.
Hope this helps in some way!
Joe