Rev 4 Motherboard not starting properly and no beep

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Rev 4 Motherboard not starting properly and no beep

see pics, I get the ampersands and no beep from the speaker.

Things I've tried:

Different power supply
gently pulling all accessible chips up and reinserting
replacing CPU chip

Also I replaced all the Roms from another board because 3 of the roms had rusty pins that broke off.

would love to get it working but no matter what I do I get the same powerup screen so there must be a bad chip or memory.

Should I try replacing all the memory or a different approach?

Thanks

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Joined: Dec 19 2008 - 21:01
Re: Rev 4 Motherboard not starting properly and no beep

The usual troubleshooting applies if you are going to attempt "shot gun" repairs (i.e. without the use of a probe or scope and schematics).

First remove all RAM except the first bank, see if anything changes. If not, replace that bank with other chips. Look for any differences in behavior. Double and triple check that you have no legs bent, and you have the chips in the right way, or they will be dead as soon as you hit power.

If no change, you don't have a RAM problem. It could be a lot of things. You are getting stable raster and some output to the screen though, so some can be excluded. SpeedyG has a method he may chime in with depending on the screen output.

If you had corrosion and legs fell off, then likely this is a problem on other chips or parts of the board (sockets). It may need a complete or partial rebuild.

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Joined: Nov 16 2011 - 07:45
Re: Rev 4 Motherboard not starting properly and no beep

The startup screen shows a change every 1 Bit after 7 Bits.
This indicates bad RAM chip or trouble with one Dataline.
speedyG

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Re: Rev 4 Motherboard not starting properly and no beep

I removed all the ram and populated the first row with 'known good' ram from a working motherboard.

Now its getting -all- question marks. Still no beep

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Re: Rev 4 Motherboard not starting properly and no beep

That must not be the only mistake..... :
http://www.appleii-box.de/D04_resurection.htm

SpeedyG

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Last seen: 6 months 4 weeks ago
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Re: Rev 4 Motherboard not starting properly and no beep

Shoot I put the ram chips in the top row.

Need to put in the 0 to 16k

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Re: Rev 4 Motherboard not starting properly and no beep

OK with one row of good RAM, I get repeating @@??@@??@@??@@??

Now when I hit RESET, I hear a double beep! And for a split second I see a 'monitor mode' address but then the screen turns black.

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Re: Rev 4 Motherboard not starting properly and no beep

Then you still have a problem with one of the ROMchips itself or its selection ( decoding of its adress )
while loading Applesoft Basic ( 74LS138 at position F12 )

SpeedyG

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