Atari XE Game system boots only to self test

[davekre]

I recently bought an Atari XE game system. When I turn it on it goes right into self test. The result of the self-test is that the ROM 'slot' on the left side of the screen is green (good) but the ROM 'slot' on the right is bad (red). All of the RAM blocks show up as good (though interestingly only 40 blocks show up whereas I think it should have 48K of RAM?). I get this same result every time I turn it on or reset it.

I have tried starting the computer while holding 'Select' and the exact same thing happens.

I am confident the power supply is good. I am actually using a 5V power supply for an Atari 800XL I have and it works for the XL just fine.

I took the motherboard out of the case and can see no obvious damage (I am not an electronics or computer person by training however). I booted the computer while out of the case and it still goes right to self test.

I tried numerous games and none worked except one (see next paragraph). I know the games are good because they work on my XL.

The one game that does work is Star Raiders. I saw something online about how this has some special testing (?) component but I do not understand the implication of this.  Can someone explain this to me?

I have the keyboard piece and it seems to work as I can use it to do various things when playing Star Raiders. But pressing the 'Help' button on the keyboard during the self test does nothing.

 

The XE boots exactly the same (to the self test) with or without the keyboard attached.

I've left the computer on for maybe 15 minutes as it repeatedly goes through the self test and some of the chips get warm but not particularly hot.

Can anyone help me get this to boot correctly?

 

I would love to get this working!

Thanks,
David K

[StickJock]

My understanding is that Star Raiders is "self-contained" in that it does not use any of the OS code.  In that respect, it is used to test machines that do not boot where the OS ROM may be suspect.

 

In your case, you have two indications that it is the OS ROM that is bad.  1) The self test tells you that it is bad, and 2) Star Raiders works.

 

There's a good chance that a ROM swap will get you up & running!

 

[+Nezgar]

Only seeing 40 blocks in the RAM test is the result of BASIC still being enabled. You can try to disable by holding option on powerup, and the other 8 blocks may show up.

 

The OS ROM chip is nutorious for going bad in the XEGS. Star Raiders has a flag that bypasses a lot of the OS startup routines and jumps right to the game code, so it is more likely to "try" to work on a failing system.

 

The OS ROM can be directly replaced with an appropriately programmed 27256 type EPROM, but your existing one is most probably soldered directly to the motherboard so will take some effort and care to cleanly desolder it, replace with a socket and EPROM.

 

I can mail you a a programmed replacement & socket if you are comfortable with the soldering required... You could save some effort by just cutting all the pins off of the existing chip to start with...

[davekre]

Thanks for your help!

 

So it seem like from what you and Stickjock are saying the OS chip is likely bad.  In the attached picture I believe that is the chip labeled AMI 8727MAA.  Is that correct?

 

I pressed "option" on startup and did get 48 RAM blocks.

 

You are correct that the chip is soldered to the board. I do not do a lot of soldering but would be willing to try with a new chip.  How do I arrange to get the replacement chip and socket and what is the approximate cost?

 

David

 

44 minutes ago, Nezgar said:

Only seeing 40 blocks in the RAM test is the result of BASIC still being enabled. You can try to disable by holding option on powerup, and the other 8 blocks may show up.

 

The OS ROM chip is nutorious for going bad in the XEGS. Star Raiders has a flag that bypasses a lot of the OS startup routines and jumps right to the game code, so it is more likely to "try" to work on a failing system.

 

The OS ROM can be directly replaced with an appropriately programmed 27256 type EPROM, but your existing one is most probably soldered directly to the motherboard so will take some effort and care to cleanly desolder it, replace with a socket and EPROM.

 

I can mail you a a programmed replacement & socket if you are comfortable with the soldering required... You could save some effort by just cutting all the pins off of the existing chip to start with...

 

[xrbrevin]

Be patient when desoldering XE PCBs - make sure the chip pins are loose before you prise the chip up.

Some were built at a lower cost and their traces can easily lift.

[StickJock]

40 minutes ago, xrbrevin said:

Be patient when desoldering XE PCBs - make sure the chip pins are loose before you prise the chip up.

Some were built at a lower cost and their traces can easily lift.

Yeah, I recommend following Nezgar's advice and cut each pin on the ROM.  That way, you are only desoldering a bunch of individual pins instead of trying to desolder them all at the same time to remove the ROM in one piece.  You are throwing it away anyway, so there's no downside and a big upside.

 

[xrbrevin]

yes good idea, and use tweezers to lift out the remains of the cut pins

[TGB1718]

What a difference in build quality, was like walking on eggs desoldering chips in my 130XE,

today on my STE, built like a tank, no chance of lifting a track

 

Take real care

[+Nezgar]

2 hours ago, davekre said:

I do not do a lot of soldering but would be willing to try with a new chip.  How do I arrange to get the replacement chip and socket and what is the approximate cost?

PM Sent. Last remote possibility is a bad MMU... but we'll start with the OS ROM.

[davekre]

So I was able to remove the old chip and solder in the new socket.  I want to test it but I am not sure which way to put the new chip I got from Nezgar in.  I am concerned if I put it in "backwards" it could damage something - the chip itself or other parts of the computer.  Can anyone tell me, looking at the attached pictures, which is the right way to insert the new chip.  And if it doesn't matter - let me know as well.

David

[StickJock]

See the little notch in the edge of the chip?  That is the orientation indicator.  With the notch on the left, pin #1 is the left-most pin below it.  The silkscreen on the PCB also shows this little notch.  Just match the notch on the chip with the notch on the silkscreen.

 

Edit:  Scrolling back, your earlier post #4 shows the PCB prior to you removing the old ROM.  It shows the notch to the left.  Just match the new chip to the old pic of your board.

Edited September 30, 2020 by StickJock
referencing your old pic

[davekre]

Now that you point out the notch as the orientation indicator it seems obvious.  But it wasn't to a novice like me so THANKS.

 

I tested it - very worried about whether my soldering job would work... and it did!!!  I now have a working XE game system!!  I am super excited and very grateful for your help.  

 

The advice about it being a problem with the OS chip was right on!  Once that was replaced it works very well - with nice crisp graphics and clear sound.  The keyboard when plugged in enables BASIC.  So it seems to be working perfectly!

 

The suggestion to cut the pins on the bad chip was good advice to help avoid damaging the board itself when desoldering. I had all sorts of issues desoldering it so I'm glad I could work on one part at a time and ease it out piece by piece.

 

I am really appreciative for all of your help and especially to Nezgar for the replacement OS chip at such a reasonable price!

 

Thanks,

David

[+Nezgar]

Good work and congrats @davekre! I recall consciously checking to print "XEGS" on the label in the correct orientation.