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XEGS shows black screen, troubleshooting tips?


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#1 flashbackmatt OFFLINE  

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Posted Sun May 28, 2017 11:06 AM

I bought a XEGS (console only) that only shows a black screen, both using composite and RF. I tested it with a good power supply from my 800XL and a working Joust cartridge.

 

Nothing looks obviously damaged/burnt on the board. Any suggestions on where to start?



#2 Paul Westphal OFFLINE  

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Posted Sun May 28, 2017 3:32 PM

Check the RAM. If it says " MT" replace immediately, but it's probably already out. Lower left side of board, two chips. Be careful, the traces are VERY easy to pull up because the mobo is so cheap. I use a $269 Hakko and it is still sketchy.



#3 jaybird3rd OFFLINE  

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Posted Sun May 28, 2017 4:12 PM

The last time I had an XEGS with this problem, it turned out to be bad RAM and a bad CPU.  I think the machine had been used with the wrong power supply.



#4 flashbackmatt OFFLINE  

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Posted Sun May 28, 2017 6:57 PM

The last time I had an XEGS with this problem, it turned out to be bad RAM and a bad CPU.  I think the machine had been used with the wrong power supply.

Thanks! I'll get replacement RAM and some sockets. The CPU is not a standard 6502, right? I would need a replacement from another 8-bit?



#5 jaybird3rd OFFLINE  

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Posted Sun May 28, 2017 7:07 PM

Thanks! I'll get replacement RAM and some sockets. The CPU is not a standard 6502, right? I would need a replacement from another 8-bit?

The "Sally" 6502 variant used in the Atari computers is slightly different from a standard 6502.  Hopefully you won't need one, but if you do, they're not hard to find; B&C ComputerVisions sells them for $5 $8 each.



#6 flashbackmatt OFFLINE  

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Posted Sun May 28, 2017 7:18 PM

The "Sally" 6502 variant used in the Atari computers is slightly different from a standard 6502.  Hopefully you won't need one, but if you do, they're not hard to find; B&C ComputerVisions sells them for $5 each.

ICG004   RAM 256K 150NS (SET OF 8)41256  25.00
ICA377   800 CPU 6502                    5.00

Thanks again. Those are the RAM and CPU that will work in the XEGS?



#7 jaybird3rd OFFLINE  

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Posted Sun May 28, 2017 7:35 PM

I might have been mistaken ... the CPU you quoted is the original Atari 800 CPU, which (IIRC) is a standard 6502.  The CPU used in the XL and XE machines (the "Sally") is $8 instead of $5.  Also, the RAM you quoted is 1-bit DRAM, the type used in the 800XL, while the XEGS uses 4-bit DRAM (that's why it only has two RAM chips instead of eight).  I believe these are the correct parts:

 

ICG464   RAM 41464 4X64K DRAM            5.00

ICA806   XL CPU                          8.00

 

(Of course, you'll want to contact them and find out for sure.  Best Electronics is another source that should have what you need.)



#8 Rybags OFFLINE  

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Posted Sun May 28, 2017 8:47 PM

They're the right items, the Ram looks a bit pricey if that's per chip.

I've got probably 20 spare of that type, old ISA graphics cards are a great source though you barely see that old stuff around now.



#9 flashbackmatt OFFLINE  

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Posted Mon Nov 6, 2017 9:04 PM

So. I finally got around to socketing and replacing the RAM, but I cracked C20 in the process. I assumed it is a filter cap, so not critical. Still black screen. I have a replacement CPU, but I'm not certain which 40-pin DIP is the CPU.

 

Can anyone tell me the specs on C20 and which chip is the CPU?



#10 Level42 OFFLINE  

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Posted Mon Nov 6, 2017 11:52 PM

U5 C014806 is Sally

Edited by Level42, Mon Nov 6, 2017 11:53 PM.


#11 rdea6 OFFLINE  

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Posted Tue Nov 7, 2017 12:25 AM

@ flashbackmatt

 

Have you tried to boot without the CART Joust installed  in the Cart slot.??



#12 flashbackmatt OFFLINE  

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Posted Fri Nov 10, 2017 3:13 PM

@ flashbackmatt

 

Have you tried to boot without the CART Joust installed  in the Cart slot.??

Yes. I have tried without cartridge, just a blank screen.






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