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Apple II+ pure white screen?

zezba9000

Well-known member
So I'm having a problem still after adding a disk-drive interface card. It stops reading drive and spits garbage data similar to @bibilit issue he shared here.

FYI: Frogger I loaded above was done via tape input.  Many times loading from tapes will have the same/similar issue.

What I do:

* Power on computer with drive and Mario Bros disk mounted with FloppyEmu

* Computer beeps

* Computer beeps AGAIN but spits out junk similar to @bibilit issue he shared.

* Drive stops being read and game never loads

What I've tested:

* Drive works perfect in known fully working Apple II+ motherboard and Apple IIe computer.

* I tested ever single chip with known good ones from Apple II+ motherboard. RAM etc is all good.

* The 74LS283 was not the issue as I hoped like bibilit had.

* If I turn on the computer with no disk mounted THEN mount a disk it SOMETIMES will load BUT text is messed up in some apps

I'm currently deep cleaning the motherboard to see if anything changed.

I'll take a picture of what it displays after its cleaned but if anyone has any ideas what could cause this when all chips are confirmed working.

 
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bibilit

Well-known member
If you can, try a copy of MECC inspector or similar, to test ram an Rom. 

A single bad ram chip can do that, I know that you are confident ram is ok, but I have seen ram becoming bad pretty quickly. 

 

zezba9000

Well-known member
If you can, try a copy of MECC inspector or similar, to test ram an Rom. 

A single bad ram chip can do that, I know that you are confident ram is ok, but I have seen ram becoming bad pretty quickly. 
You're right I had 3 bad ram chips. Guess I tested wrong last time.

Now its 100% stable and working! Ran it for an hour with no issues.

I also added some heat-sinks on chips that got hot. Hopefully it keeps them from overheating and lasting longer.

image.png

Also modified my FloppyEmu cable so I can easily attach "DISK ][" drive cables

image.png

 

techknight

Well-known member
What was the chip type/number of the chip you replaced out of curiosity? (I am taking a tally mentally from all the different repair experiences, and so far Ive found the LS138 to be less than reliable)

 

zezba9000

Well-known member
What was the chip type/number of the chip you replaced out of curiosity? (I am taking a tally mentally from all the different repair experiences, and so far Ive found the LS138 to be less than reliable)
Besides the bad ram the bad logic chip was: SN74LS153 to the right of the last upper row of ram as you can see in the picture.

 

techknight

Well-known member
ok yea the 153s are dropping like flies too, especially in Arcade boards. 

 
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zezba9000

Well-known member
ok yea the 153s are dropping like flies too, especially in Arcade boards. 
You also keep track of how many people had these go bad while using original PSU?

The Apple ][+ I got had a bad PSU making a clicking sound with voltages not good. Now that I replaced it with a custom PICO based one my guess is there will be less issues down the line.

I have original PSUs for Apple IIe & III and if the there are parts on the legacy PSUs that are the root of the problem I wan't to replace those at some point.

All these PSUs have a mechanical part that makes some noise that to me feels like could be a possible longer term issue for these computers.

 

techknight

Well-known member
You also keep track of how many people had these go bad while using original PSU?

The Apple ][+ I got had a bad PSU making a clicking sound with voltages not good. Now that I replaced it with a custom PICO based one my guess is there will be less issues down the line.

I have original PSUs for Apple IIe & III and if the there are parts on the legacy PSUs that are the root of the problem I wan't to replace those at some point.

All these PSUs have a mechanical part that makes some noise that to me feels like could be a possible longer term issue for these computers.
Nope, im only keeping a tally of failed electronics "in general" when it comes to logic ICs. nothing product-specific. 

 
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