Apple IIe Video Display Problem

[mikerm]

I recently got an Apple IIe, but when I turn her on I get 5 large "bars" of a solid ASCII character across the screen. I took apart the entire machine and cleaned it. I also re-seated all of the chips. I tried it with and without the 80 col card and got the same results.

Holding down the Reset key while turning on presents a different screen of random blocky ASCII characters (but not what I've seen pictures of what it's supposed to look like).

I tested the power supply voltages, and they seem to be ok. Any ideas? I did a bunch of searching on Google and in here and couldn't find anything.

Edit: Couple more things, there is a power light, there is no beep.

 

[lotonah]

Not an expert, but it sounds like the ROMS have a problem (possibly bit rot?)

If it is, you can get replacement ROMS from ReactiveMicro. Here is a link to the replacement Enhanced ROMS.

 

[dorkbert]

trying doing the three finger solute (ctrl-open apple-reset) and see if the built in self test comes up.
Edit - That would be closed apple key, not open apple.

 

[channelmaniac]

4 fingers for diagnostics... Ctrl-Open Apple-Closed Apple-Reset

3 fingers for reboot.

Or if you want to loop the diagnostics then just open the top and unplug the keyboard before you power it up. It'll loop forever unless it finds an error.

Bars on the screen like that can be caused by bad power supply, CPU, memory, MMU, ROMs, or any other chip that could cause the system to not boot properly.

I'd start with testing the +5v line to make sure it's right. If it's not between 4.75 and 5.25 then things won't work right. The power supplies in those systems are known for having a small electrolytic capacitor fail in the feedback section. When that happens the power supply will either shut down or not put out enough voltage.

There's also a 1/2 watt resistor in there that gets crispy. The size of the resistor depends on the model of supply. Apple used 2 different manufacturers. Astec is harder to work on but safer. The other no-name power supply board DOES NOT HAVE BLEEDER RESISTORS ACROSS THE MAIN FILTER CAPS!!!! This means that you have to be extra careful when working on that model since the caps WILL hold a charge for hours.

Raymond

 

[channelmaniac]

Forgot to mention... the built-in diagnostics are brain dead. If it finds an error, it puts it up on the screen and halts. It will NOT show you all the bad chips at once. Replace the bad chip, re-run the test to see if any more are bad, and re-run it until it finishes with no errors.