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Help needed: 130XE boots to ROM/RAM self test


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#1 Macross_VF1 OFFLINE  

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Posted Tue Feb 12, 2019 10:51 AM

Just picked up an 130XE and it doesn't quite work as intended. It immediately boots into the ROM/RAM self test and doesn't respond much to keyboard input. In the self test it claims the second ROM to be faulty, which seems legit since I can't get access to the Basic prompt. Note that all the RAM tests out fine I just didn't wait for it reach the end in the picture below.

 
However I can't reach the rest of the self test screen. Pressing option when powering on makes no difference and pressing help on the keyboard does nothing. Only reset works, though only to restart the ROM/RAM self test.
 
I have one game cartridge, Moon Patrol, that works, though I can't properly start the game. Pressing 1 makes the game play itself, and reset does exactly that, though no other input seem to work. Do I have a faulty keyboard?
 
On a side note, I also have three XEGS game cartridges and they do not seem to work with this system, though admittedly I'm fairly certain one is broken to begin with.
 
Finally, I've opened up the system and found a few wires that do not seem like they normally should be there. Is it a factory bodge job or has someone tried a repair?

 

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#2 _The Doctor__ ONLINE  

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Posted Tue Feb 12, 2019 12:02 PM

yes they are factory the 74ls08 the wires go to needs to be a 74act08 or an hct in a pinch


Edited by _The Doctor__, Tue Feb 12, 2019 12:03 PM.


#3 _The Doctor__ ONLINE  

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Posted Tue Feb 12, 2019 12:08 PM

the 4050 74lso8 and 74ls138 have been know to go bad, I'd double check the socketed chips making sure the sockets haven't fail or developed weak swipes and or cold or cracked joints on the board, retouch the socket joints with the chip out, as the heat can soften the plastic when still under pressure from holding the chip and then weaken to be useless even if it was already good... it won't be afterwards..



#4 _The Doctor__ ONLINE  

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Posted Tue Feb 12, 2019 12:09 PM

does all of the ram tests good to the end?

it's possible the rom is bad,

make sure the power supply didn't cook it, test the voltage under load.

what does the power supply look like?


Edited by _The Doctor__, Tue Feb 12, 2019 12:12 PM.


#5 Macross_VF1 OFFLINE  

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Posted Tue Feb 12, 2019 1:41 PM

does all of the ram tests good to the end?

it's possible the rom is bad,

make sure the power supply didn't cook it, test the voltage under load.

what does the power supply look like?

Yup, the ram checks out, I just didn't wait for it when I took the photo.

The ROM does seem to be bad, so I suppose the next step will be to replace it. However, could a bad basic ROM cause the keyboard problems? I've tried manipulating the connector on the motherboard directly, thus bypassing the keyboard completely, and it doesn't seem to make a difference.

As for the PSU, I'm currently using one from a 600XL. It does work as intended and outputs the proper voltage. Am I to assume that the PSU is a common failure point with this line of computers, just like the C64 PSU is known to be crap?
 



#6 _The Doctor__ ONLINE  

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Posted Tue Feb 12, 2019 2:11 PM

do not fiddle with xe ribbon cable, it's fragile and you can make micro fissures in the mylars traces. it can be ruined and your keyboard won't work, you would have to spend some dollars to replace the mylar or keyboard...

 

did you try a basic cartridge or star raiders cartridge?

 

you may have a bad rom in any event, but trying those things will let you know some other things about your XE


Edited by _The Doctor__, Tue Feb 12, 2019 2:13 PM.


#7 Macross_VF1 OFFLINE  

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Posted Tue Feb 12, 2019 4:32 PM

Unfortunately I don't have any more cartridges than the ones I have already mentioned above nor do I have any other software available. It is times like this I kinda wish I had spent more time collecting games instead of just focusing on hardware.



#8 Sugarland OFFLINE  

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Posted Wed Feb 13, 2019 3:30 PM

If you open up the keyboard (lots of screws on back side) you can give a visual inspection of the carbon keypads and traces. Often the pads are worn very thin and the traces aren't in good shape. Some conductive paint will fix it if you have some. If you don't have conductive paint I don't recommend spending money on it. Rather get a $20 mylar replacement off ebay since it will work and not fail again in a year or two. There are two mylar types so be sure you have the right one.  Good idea to fix the ROM or whatever that problem is first just in case that's causing the keyboard to misbehave.


Edited by Sugarland, Wed Feb 13, 2019 3:33 PM.


#9 tf_hh OFFLINE  

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Posted Thu Feb 14, 2019 8:19 AM

Just picked up an 130XE and it doesn't quite work as intended. It immediately boots into the ROM/RAM self test and doesn't respond much to keyboard input. In the self test it claims the second ROM to be faulty, which seems legit since I can't get access to the Basic prompt. Note that all the RAM tests out fine I just didn't wait for it reach the end in the picture below.

 

1st, there´s no second ROM - the left block indicates the frist 8 KByte of the O.S. ROM area between $C000 and $DFFF (incl. Selftest mirrored from $D000-$D7FF to $5000-$57FF) and the right block shows the checksum test result of the $E000-$FFFF area (also 8 KB). The complete 16 KB are located in one chip. The BASIC ROM was not recognized by the Selftest.

 

Because the computer boots straight into the Selftest, but shows no defect RAMs, IMHO only three options possible:

 

- Just a bloody simple short to ground (read below)

- Defect O.S. ROM

- Defect MMU

 

This order beginning with the upmost probability ;-)

 

What I mean with the first bullet point is: Check first if only a short-circuit of one of the cartridge´s / ECI´s connector pins has contact to the metal grounding plate. I´ve seen many XE systems, where the pins aren´t shortened (cutted), specially at the ECI port (2x 7 pins). Atari didn´t insert any fishpaper between the metal plate and PCB, so if there´s one of the pins too long, it might have contact to ground in same cases. Sometimes the computer doesn´t boot, sometimes this failure happens..

 

So simply re-test the board without metal plate loose, when the XE boots into READY prompt, you know what to do - cut the too long pins, that´s all.



#10 Macross_VF1 OFFLINE  

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Posted Thu Feb 14, 2019 12:57 PM

 

1st, there´s no second ROM - the left block indicates the frist 8 KByte of the O.S. ROM area between $C000 and $DFFF (incl. Selftest mirrored from $D000-$D7FF to $5000-$57FF) and the right block shows the checksum test result of the $E000-$FFFF area (also 8 KB). The complete 16 KB are located in one chip. The BASIC ROM was not recognized by the Selftest.

 

Because the computer boots straight into the Selftest, but shows no defect RAMs, IMHO only three options possible:

 

- Just a bloody simple short to ground (read below)

- Defect O.S. ROM

- Defect MMU

 

This order beginning with the upmost probability ;-)

 

What I mean with the first bullet point is: Check first if only a short-circuit of one of the cartridge´s / ECI´s connector pins has contact to the metal grounding plate. I´ve seen many XE systems, where the pins aren´t shortened (cutted), specially at the ECI port (2x 7 pins). Atari didn´t insert any fishpaper between the metal plate and PCB, so if there´s one of the pins too long, it might have contact to ground in same cases. Sometimes the computer doesn´t boot, sometimes this failure happens..

 

So simply re-test the board without metal plate loose, when the XE boots into READY prompt, you know what to do - cut the too long pins, that´s all.

I've been told elsewhere just that, no second ROM. Supposedly it's a relic from the 1200XL where the ROMS actually were two separate chips or something? 

Anyway, I think I've located the spot you are referring to, and no it does not seem to connect to the bottom RF shield. Just to be sure I removed the shield entirely but sadly no improvement. So yeah, the OS ROM is likely the culprit. I have a 600XL that I can swap chips with in order to test the problem, though I have to get some IC sockets first.






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