No power on iie motherboard help (power supply does work)

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No power on iie motherboard help (power supply does work)

 Hello,

I'm looking for info on how to go about troubleshooting this apple iie motherboard I'm working on that isn't powering up. The power supply works and confirmed in full working order. Motherboard isn't even getting the led lit up when power is on sadly. I was wondering if anyone here would have some pointers as to common problems causing this please? I do have a multimeter and can follow along with most suggestions anyone might have.

 I've plugged it in to a monitor and there is nothing. Neither the motherboard or keyboard led lights up. I've reseated all the socketed chips (it's a fully socketed '82 board) as well as removed all expansion cards to run the power on test. I've been told there could be a short on the board but even after a look at a couple schematics I'm at a loss as to where to even start.

 

Thanks!

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Measure voltages

Measure voltages across all ICs and traces leading to the led.

That might give you an idea if there is a broken trace or bad soldier joint somewhere.

And look out for a shorted resistors, capacitors etc. which will prevent any voltages.

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From your description, there

From your description, there is either an issue with power getting to the motherboard (open/loose connection) or a short which s shutting dowm the power supply. This can easily be determined by measuring the voltages at the power connector or the supply caps C9, C12, C17, and C15. Most likely you will find a short and one of those caps may be the culprit.

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Thanks! Someone else also

Thanks! Someone else also suggested the same so I will be looking at exactly that.

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Getting a whole lot of

Getting a whole lot of nothing. Perhaps that means L1,L2,etc are bad?

 

EDIT: Looks like C12 is dead. I might just reaplace all 4 of these caps at once. Anyone know the value

of  C9 and C17? I already found out that C12 and C15 are 10uf 16v from other reading. I can't see

the markings on the cap on the board. Perhaps when I remove them I will see the marking clearer.

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10uf 6.3v on the little guys

10uf 6.3v on the little guys for the 5v lines it seems. I replaced the 2 attached to the 12v lines and I now have power. :)

 

 

EDIT:

 

 

OK, It's up and running now BUT one of the graphic modes is all wonky. text on boot up is crazy, self test is squares and then wonky text. Karateka plays ok from disk but you can still see a few graphical errors, specifically vertical lines. Am I correct in assuming this is probably bad DRAM? Again, thanks for the help with this. Almost fixed :)

 

 

 

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Pictures would help... Could

Pictures would help...

 

Could be RAM or other logic chip.

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Forgive my ignorance, but how

Forgive my ignorance, but how would I go about attaching photos on this forum? I will add some ASAP. I was also considering it could be a bad video rom as you sorta mentioned.

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fixing2e wrote:Forgive my
fixing2e wrote:

Forgive my ignorance, but how would I go about attaching photos on this forum? I will add some ASAP. I was also considering it could be a bad video rom as you sorta mentioned.

 Click the Media Browser when composing your post.

 

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Here is what is shown in text

Here is what is shown in text based graphics mode. This is a photo from the boot screen. The second photo  shows the machine in the other graphic mode (I think?) playing Karateka with only minor graphical issues (the vertical blank lines in the background graphics). There is ghosting in the second photo making it look worse than it actually is on screen cause my camera is a potato..lol..

 

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I read in this old thread

I read in this old thread about another users issues that seem similar to my own. The corruption shown on his ultima game looks to be the same problem I'm seeeing while testing with Karateka. (vertical blanks in the graphics being displayed). His text mode is was in a better state than mine currently is. 

 

https://www.applefritter.com/content/text-not-appearing-correctly-apple-iie

 

Just wanted to show that I did and have been reading around the forum before posting. God knows you guys have had a million folks ask the same questions a 100 different ways and I understand that might get old. It goes without saying, I very much appricate the help and pointers I've recieved so far.

 

 

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Diagnostics

Do you have diagnostics disk, so that you can run a RAM check?

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Built in

Or does the IIe have a built in test? I'm not sure.

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standard IIe

it does have a memory diagnostic test, activated by three finger salute.

 

From: https://www.applefritter.com/content/full-apple-iie-diagnostic

To run the built-in test, push both the [open apple] and [closed apple] keys on startup. Or if the machine is already running, push [open apple], [closed apple], and reset.

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I did that previously and it

I did that previously and it does the full green screen, alternating lines turn the screen to black and then the same process back to green at which point it displays garbled text which I assume is trying to say something and then "OK" at the end but it's clearly not ok. The rest of the screen has these weird dashes and lines on the screen as seen in this photo I took:

 

 

 

 

If it's a problem with any of the  3 system rom chips I do own a programmer and can burn and replace those without issue.

 

EDIT: I'm also wondering if anyone can confirm that " Hitachi HM4864-3 " DRAM is compatible with the iie please? I can get some of those pretty easily if needed but don't want to purchase them if they are not of use (obviously).

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fixing2e wrote:I did that
fixing2e wrote:

I did that previously and it does the full green screen, alternating lines turn the screen to black and then the same process back to green at which point it displays garbled text which I assume is trying to say something and then "OK" at the end but it's clearly not ok. The rest of the screen has these weird dashes and lines on the screen as seen in this photo I took:

&nbs

It would be nice if your screen shot photos were in focus.

 

The IIe diagnostics tests memory.  The memory for test page 1 and 2 should have the same character, top to bottom of the screen.  Hires screen memory should have solid alternating black and white columns with no artifacts in the b&w columns.

 

If there are ANY anomolies to the above on the screen, depending on where they are happening on the screen, they indicate faulty memory or memory chip connections.

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If you say you can play

If you say you can play Karateka without the machine crashing, but the text-mode screens are completely garbled - and the graphics screen has smaller artifacts, then this makes an issue with the video logic at least more likely than a gerneal RAM issue. Could be the connection between the data bus and the video logic - or any other logic chip involved. Garbled text is also often caused by a bad video ROM. However, a bad video ROM normally doesn't cause issues in graphics mode.

Yep, as was previously said: it'd be helpful if the photos clearly showed which characters are being displayed (boot screen). Sometimes this allows to tell exactly which bit(s) are stuck.

Still, it will remain a guessing game...

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MacFly wrote:However, a bad
MacFly wrote:

However, a bad video ROM normally doesn't cause issues in graphics mode.

 Actually the graphics video data also goes through the VIDEO ROM, so that could be the cause of all your issues. The LS166 at position F5 would also be worth checking.

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With testing of the LS166

With testing of the LS166 what would be the method? As for the Video ROM I will burn a new one and try that as I have the parts on hand to do so.

EDIT: Looks like the video rom is actual a 2732 so I'll have to order one. Smallest I have on hand is 28 pin eproms and I don't want to be rerouting address lines on the chip as I want to keep this clean. This is a friends lifelong family machine. Gotta keep it as pretty as possible for him. I'm doing this as a favor for them.

 

As for the self test results that the other user mentioned, there is no artifacting at all when it switches from green to black and back to green (aka white).

 

This is the clearest pic I could get of the screen at the end of the self test:

 

 

Here is a second photo of that screen, which one is better I'm unsure. 

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I burned a new video rom and

I burned a new video rom and that fixed all the graphical issues. Turns out the text on that self test was trying to say "Kernel OK" now that I can actually see it. Thanks to all for the pointers and guidance. 

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