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First Apple 2e in 20 years! Vertical bars on boot

bobba84

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Hi guys,

So, I've finally got another Apple 2e! The PSU is dead but that's another issue. I've got a bench supply running it at the moment.

What does it mean when booting gives these vertical lines? Any repair flowcharts available, etc? Or any common causes?

Thanks in advance for any help!!

apple.jpg
 

bobba84

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Interesting!

I pulled the CPU and I get clean bars. When it's inserted I get this:

IMG_9634.jpg

Does this still look like CPU issues? I swapped a few of the RAM chips around (first to last etc) and it didn't make any difference.

Here's the board for reference:
https://imgur.com/a/QXaqlAy

Also, neither of the LED's ever come on. Is this still consistent with a bad CPU?

I have reseated all removable chips already.

Where could I get another CPU? eBay?

Bobby.
 

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Last edited:

SomeGuy

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The way Apple II computers work, seeing random garbage like that on the screen means that the CPU is not running, so you are left looking at the uninitialized content of the RAM used by the video. Unfortunately, there are a number of reasons the CPU may not be running besides the CPU itself.

The first thing I would do is carefully clean the board, and inspect all chips and sockets to make sure all socketed components are making good connections. Given the corrosion that appears to be present on the video/cassette ports I would not be surprised if that is the entire problems. On an Apple II Plus board, I had to check each socket/leg with an ohm meter until I found one that wasn't making contact even though it looked fine.

I'm not sure how to troubleshoot a IIe board other than to just switch around chips with a known good board. You could certainly try a different CPU but there is a high probability the fault lies elsewhere.

I forget, will a IIe board do anything at all if RAM is sufficiently bad?
 

KC9UDX

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If you disconnect the keyboard, it should try to run the self diagnostic. Whether it does anything useful though depends on a good number of things working. You can buy a brand new microprocessor. The 65c02 is still in production. I'd say you could get one from Jameco because that's where I buy them, but I don't think they sell them anymore. I'll be surprised if that helps though. 6502s just aren't that failure-prone, but there are a plethora of other things that could be causing trouble. If I were to shotgun replace anything, it would be the RAM.
 

bobba84

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Thanks for all the help so far guys!

I've tried a different CPU, no difference.

I also replaced the first three logic IC's from this guide that I found online.

I tried some 4164 RAM I had lying around (in a 286 board that the battery had corroded) and it make even more junk appear on the screen instead of starting with clean white bars and slowly corrupting like it did before. So I put the original RAM back in.

I've cleaned the board and looked closely for bad tracks, but haven't found any.

One thing I did find though, was a burnt capacitor. (C55) - it's a small tantalum (I think) that says A5E 104 Z

Removing it made no difference - does anyone know if this is required?? If so, I'll grab a replacement.

If not, there's one other thing concerning me. The 2nd LED flashes once when power is turned on, but the first main power LED never lights up. Does that mean something is shorting one of the power rails? Or could it point to another problem?

Thanks again for all the help received so far guys!!
 

KC9UDX

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What you've proven is that your two different sets of RAM chips differ. So some amount of your RAM is certainly bad. Not having a second computer to try the RAM in, I'd be inclined to buy another whole set of chips.

The one LED blinking at power up may be the speaker beep which you're supposed to get. I don't recall what the other LED signifies.
 

bobba84

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I think it's supposed to be on all the time.

I'll obtain some new RAM chips and try again... but I don't think bad RAM would cause the LED to stop glowing.

I desoldered the four capacitors near the power connector but the behaviour didn't change...

Thanks!
 

SomeGuy

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A different pattern with different ram chips only proves that the ram chips have different default uninitialized states. Every chip is slightly different. Different manufactures, even more so. The initialized state, however, is irrelevant to the operation of a computer.

If the capacitor is directly between ground and a power rail, then that would not be the cause. It should operate without those.

Since you are getting video, you are getting power. If you are concerned about the power, simply use a volt meter to verity the voltages are around what they should be. A short would usually either prevent a power supply from starting up or make something go boom.
 

groink

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I'm wondering if maybe the CPU is technically good, but something is causing it to either constantly reset, or never reset. Normally, when the 65x02 is powered up, it is in a state where it needs a reset, hence the autostart operation on the Apple IIe. The autostart involves pulling the reset pin low, then quickly pulling it back up to complete the reset cycle. If you had a logic probe, you would be able to monitor the state of the reset pin, and see if it actually does reset upon power up.

If the CPU reset pin 40 is constantly low after power on, it may cause the CPU to have a non-operational effect, although this would normally show text garbage and not the bars. Which leads me to think the other possibility which is if something is interfering with the reset circuit. Have you tried CTRL-RESET, and if so does it have an effect on the display?
 

bobba84

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I'm wondering if maybe the CPU is technically good, but something is causing it to either constantly reset, or never reset. Normally, when the 65x02 is powered up, it is in a state where it needs a reset, hence the autostart operation on the Apple IIe. The autostart involves pulling the reset pin low, then quickly pulling it back up to complete the reset cycle. If you had a logic probe, you would be able to monitor the state of the reset pin, and see if it actually does reset upon power up.

If the CPU reset pin 40 is constantly low after power on, it may cause the CPU to have a non-operational effect, although this would normally show text garbage and not the bars. Which leads me to think the other possibility which is if something is interfering with the reset circuit. Have you tried CTRL-RESET, and if so does it have an effect on the display?

Interesting. I actually have a logic probe on it's way to me in the mail (when it arrives I'll have to learn how it works) but no, CTRL+RESET does nothing.
 

VERAULT

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This screen shows whenever I have CPU problems.

Everyone told me this when I was fixing my first II Plus unit. I know the boards are different but it wasnt the CPU at all (tried a working CPU from my commodore PET same issue) turned out to be a bad TTL logic chip.
 

3pcedev

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That pattern also can indicate a bad CD or EF ROM.

I had exactly the same problem and spent too long chasing a possible fault with the CPU / RAM and bus glue logic. Burned a new EF rom and the machine booted immediately.
 

bobba84

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I just went to the local parts store and bought 8 4164's and a whole bunch of 74xx chips. Hopefully a chip swap will yield results! :)

If not... My ROM burner is stuffed. Is there anybody (in Australia hopefully) that could burn me new ROM's? :D I'll pay of course.
 

3pcedev

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I can burn ROM's - however my current stock of 27Cxxx chips is at zero. There would be a little wait as I would need to buy some more.

Modem7 can also burn ROM's in Australia. He based in Melbourne so shipping should be cheap. Try sending him a PM.
 

bobba84

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Argh... I just found one of the crystals has a broken leg!

It's the one to the right of the board. It says NDK 0443 4.433619 on it

I'm guessing this is the one of the two crystals that provides the CPU with a clock? :|

Time to find a replacement.
 
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