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

bobba84

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No luck. I've replaced the crystal, and every logic IC, and the RAM, and the CPU. Still weird block patterns and corruption.

I've ordered some ROM's from modem7 - let's try that :/
 

bobba84

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Ok guys got an update...

Still not working!!

I've replaced the CD, EF and Video ROM's (thanks modem7) as well as the RAM and tried replacing every LSxxx chip

Volts are good, CPU Pin 7 has a clock, Reset pin goes low-high on boot and stays high.

What on earth else could be wrong?

thumbnail_IMG_9855.jpg
 

KC9UDX

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Is there an easy way to check MMU? I don't recall.. Maybe by pulling the 6502, you can force addresses and see what it does.
 

bobba84

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I wouldn't know how... I have a logic probe finally. Anyone know how to do this?

If it's bad, where would I get another MMU?

Another update: Does this look like it's actually running something (like the self test)? It isn't legible, but seems to be doing 'something'... is this a clue?

http://www.youtube.com/watch?v=K_kglXf3R7I

Edit: I'm still confused as to why the Power LED doesn't light up. Is this software controlled?
 

3pcedev

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Earlier you mentioned you were using a bench supply to power it. What sort of bench supply are you using to power the unit?

The factory supply has +12 +5 -5 -12 rails. Are you 100% sure you have the correct voltages on all of them? If your not using a quad channel supply (i.e. using more than one supply) be very careful with your ground reference. They all need to be interconnected correctly; and some supplies don't play nicely together.

The power led is not software controlled. This points to one of your voltages being missing. I *think* it is powered by the +12 rail; although last time I checked was years ago so I could be wrong. I just have this recollection that it wasn't powered by the +5v rail...

Also check the voltages on the little axial capacitors just adjacent to the power connector on the motherboard. It's possible you have a corroded pin or broken trace in/around the power header itself.
 
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3pcedev

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Also are you checking the voltages with the PSU hooked up to the motherboard?

It's unlikely but not unheard of to have shorted capacitors on IIE motherboards. One of the voltage rails may be shorting out and causing the PSU to go into protection mode.
 

bobba84

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Hey guys,

I’ve actually fixed the 2e supply, and I’ve been tryinf with both my quad channel bench supply and the 2e one.

All voltages seem fine when it’s connected to the board. And those caps near the power plug are ok... still weird that the LED won’t light up!
 

3pcedev

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I vaguely remember the LED being triggered through some sort of 74S logic. You mentioned you replaced some 74LS chips; however the fault may be with one of the 74S ones.

Here's a troubleshooting guide that mentions some 74S logic that should be checked when the power light is not functioning (scroll down to about 1/2 way): http://www.1000bit.it/support/manuali/apple/repair2e/repair.htm

Note that you have a PAL IIE - IIRC the ID of the chips is the same (at least everything thats not video related) however the physical location differs. The troubleshooting guide should still be relevant.
 

3pcedev

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Ignore my comment above - According to the schematic linked here the power LED is definitely DIRECTLY off the 12V rail.

Try probing the +12V somewhere else on the board. There are a couple of places - one is pin 50 on the expansion slots and another is the clock generator (see link here)

My guess is that the +12 isn't making it to the clock generator......
 

bobba84

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I didn’t have replacements, but I tried equivalent 74LS’s in their place, it acted the same. Would they have not worked for testing purposes?
 

bobba84

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Update, the actual LED was bad. Replaced it and it lights up!

I’ve noticed the garbage changes around on screen the same even when the CPU is removed or changed... so no, i don’t believe anything is really happening.

12v is present on the expansion ports

Any other ideas? :)

Thanks heaps for the help so far!
 

KC9UDX

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What else is 12V powered in a //e? Whatever it is, is likely fried, too. If the clock genny is fried, there's your problem...
 

3pcedev

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Beware using logic probes on the clock input to the CPU. Depending on the probe it may not be able to handle a 1MHz signal. I chased my tail for a while thinking the internal clock generator was fried; but it was just my cheap logic probe not being able to see 'fast' pulses.

That being said if your seeing a pulse on the input it's probably ok.... although without a scope it's difficult to tell if it's clean or not.

Try your logic probe on the one of the address lines on a 4164. It will be interesting to see if it's accessing/refreshing the RAM.
 

bobba84

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Yes, there is a pulse on all address lines, as well as RAS and CAS.

I've got another (non-working) board on it's way to me, hopefully I can make one good out of two!
 
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