Atari 800XL power LED not working

[ToddL]

I opened up my 800XL recently and after putting it back together the power LED no longer works (worked fine before opening it up).

 

To my recollection, I did not remove any chips or connections while inside other than the keyboard ribbon. I was checking to see if the board has C56 and R57, and it has neither.

 

I suspected the keyboard ribbon was not connected properly so I've tried re-connecting it tighter and then looser but neither helped. The computer seems to work fine other than the power LED, including every key on the keyboard. Did I forget to re-connect something? Did I accidentally damage something?

[tjlazer]

Is it the type of keyboard that has a Mylar? It might need to be cleaned or repositioned

[+Nezgar]

Yep clean all contacts on the connector with isopropyl alcohol/qtip and/or pencil eraser. The traces on the mylar may also have a microfracture from flexing. Maybe you'll see it intermittently light if you lift it while on and connected. Check continuity on each trace. The power lead I think is on one side.

[SignGuy81]

This may help as well you trace it down.

 

http://www.atarimania.com/documents/Atari%20800XL%20Service%20manual.pdf (page 41 of 41) shows the circuit you need to look at with R95, C94, & C95. You should have 5V on one side of the resistor(R95) which is your +5A, and you should have a lower voltage(with LED working, the 5V minus whatever the voltage is dropping across the resistor depending on the voltage drop of the LED should be around 2V giver or take a bit) on the other side of the resistor. Here is a page showing the matrix for the keyboard http://blog.3b2.sk/igi/post/Tipy-a-triky-013-ATARI-XL-XE-change-keyboard-Tips-tricks.aspx make sure you look over 18(GND) and 24(24 goes to circuit I mentioned above) and trace back to LED.

[ToddL]

Thanks everyone! I cleaned the contacts on the ribbon but that didn't immediately help. With the computer turned on, if I pull or push on the ribbon, sometimes the LED will light up. But I can't get it to stay on consistently. I haven't taken apart the keyboard yet to check the other end but I suppose that's the next step.

[SignGuy81]

I doubt you need to check the other(by that I mean the voltage check and tracing the connections I mentioned) it should be fine. The problem is in the ribbon connection as the others mentioned if it comes and goes when pulling or pushing the cable. Can you take pictures(of the end of the ribbon cable and the connector)?

Edited March 28, 2018 by SignGuy81

[ToddL]

Pictures attached

Photos.zip

Edited March 28, 2018 by ToddL

[SignGuy81]

End of the ribbon looks bad. Cut off that bad part about an 1/8th of an inch(maybe just a 1/16th of an inch just enough to get to the unworn part) with scissors then plug it back in and give it a try.

Edited March 28, 2018 by SignGuy81

[xrbrevin]

it might be worth looking into the socket in case some debris fell in or a pin is adrift?

[gs80065xe]

A few weeks ago, my XE power light stopped working. As well as the shift and control keys. It was the mylar. Not sure if the XL had mylar in their keyboards. Best electronics in CA sells replacement Mylar for the XE. May want to see of they carry them for the XL.