Apple II+ boot issue: nothing but the "@" symbol

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GG
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Apple II+ boot issue: nothing but the "@" symbol

Hello – Today, my Apple II+ is having a boot issue. I’m far from being a technical person and have no diagnostic tools. Any advice would be welcome.

 

Some background on the issue: yesterday, while the computer was booting I stupidly opened the door on the disk drive and briefly removed then reinserted the boot disk. The computer, obviously, didn’t boot properly. So I shut it down and turned it back on. Everything initially seemed to be normal (it beeped and the drive was accessed) although it was as if the drive was talking to the computer but nothing was happening. This continued to happen despite multiple turn offs and ons, and multiple reseatings of the Disk II card. Eventually it booted properly. Okay great. Created a ProDOS boot disk (from Floppy EMU) and attempted to boot. It said no dice as it would only work on the IIe and IIc. Okay fine. Put the DOS 3.3 boot disk in again and it booted fine. 

 

Today, I turned it on and there is no beep, the drive isn’t accessed, and the screen shows line after line of the “@” character. After consulting the II Plus and IIe repair guide, I pulled and reseated the F8 ROM and the 6502. Nothing. I also pulled and reseated the 74S86 at B2. Nothing. All I have done is pull and reseat. I don’t have any replacement chips.

 

The computer had been in storage for nearly 20 years and within the last few weeks I replaced the PSU and keyboard encoder. All was well after that and had subsequently added a VGA card, which was also working well. As of a week ago, some diagnostic software gave the machine a clean bill of health. 

 

GG

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The all @ symbols on the

The all @ symbols on the screen is the vga card's doing. Pretty sure that is the default output when it doesn't know what to do. Which makes sense given that it sounds like the cpu isn't initialized (no beep). That's about all I can add, as I don't really have experience with a II+. 

GG
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Thank you. Makes sense. Will

Thank you. Makes sense. Will connect to an old monitor using an RCA cable and report back. 

GG
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Update

Using a monitor from a IIc, I see a pattern... WW@@WW@@ then repeat until end of row... next row is two blocks followed by HH (then repeat). 

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Makes me think of the

Makes me think of the problems I had with mine some time ago: https://www.applefritter.com/content/apple-ii-europlus-help-diagnosing-no-prompt

GG
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Thank you. I've reviewed that

Thank you. I've reviewed that thread you referenced (and a few others). Unfortunately the only thing I can do at this point is pull, clean, and reseat the chips. At this point I've done so for virtually every chip on the motherboard to no avail. In fact, the problem seems to be "worse" now (at least as measured by the output to the monitor). 

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