Atari 800xe has died

[blacka013]

Hi all,

 

I recently purchased an Atari 800xe from ebay which is heavily modded. I came to use it this morning and would not boot up, the only life showing was the power led.

 

It is modded with the following:-

 

1. 512K Memory Expansion
2. A second Pokey chip enables real stereo sound
3. Error Free GTIA Graphics controller
4. Serial(Com) SIO2PC Interface connection
5. Operating System switch
6. Memory Select switch

 

I have checked all the external connections and then substituted my old 800xl which worked.

 

I have been back to the seller, suggested checking the connections, then asked if I knew anybody who was good with computers.

 

Can anyone give me some advice fixing it please?

 

Regards

[blacka013]

I have checked all the socketed chips are seated correctly, looked for any obvious signs but can't see any. The memory chips are MT 4067-12. The screen when powered up remains black with a no signal present showing on the TV, input selected correctly. I would have included a photo of the motherboard, but not sure how to insert it into the text.

 

Regards

[Rybags]

MT Ram is the bad stuff.

 

But in this case I would guess probably something among those addons has come loose during shipping.

I'd be checking the OS and memory mods first up.

[Keatah]

Agree! Push, poke, wiggle, and reseat all the add-on stuff. Examine solder joints for add-on stuff. Then we'll consider doing other stuff.

[blacka013]

Hi Rybags and Keatah,

 

have followed your advice, still no joy.

 

I then remembered my multimeter has a frequency selection, I tried this on my 800xl and the crystals are showing just under 4 MHz.

 

I unplugged the upgrades from the 800xe motherboard and then tried this and I only get 23 KHz at best, so there is something definitely wrong in this area.

 

Any suggestions on what to check next?

 

Oh, can you explain how to upload images to the forum so you can see the board as I still can't get this to work?

 

Regards

[Keatah]

It is important to check your multimeter specification and be sure it is rated to handle the frequency of the crystal. If not, you'll get some arbitrarily low reading. Don't want to bark up the wrong tree.

[blacka013]

Th multimeter frequency will measure up to 15 MHz, the two crystal are 14.187578 and 4.433618 MHz.

 

regards

[blacka013]

Ok, have completely de-modded the 800 xe and the fault remains, next stop ram change.

[blacka013]

I have removed the ram and decided to check the output from the crystal, still as before, so there must be something on the board still dragging them down. Does anyone have any suggestions.

 

Thanks in anticipation

[zylon]

Check your CO61618 IC. It's the 20-pin one just below the cart port. I just fixed one with a similar issue. It also had the MT ram. All 8 had to be replaced as they ran too hot to touch.

 

That IC had me stumped until I used substitution with IC's from one of my 600xls

Edited May 27, 2014 by zylon

[blacka013]

Finally,

 

The problem was the Freddie chip, I substituted this from a dead 65xe I am also working on and it all works.

 

Thanks for the help, it has been much appreciated.

 

Now a dead 65 xe to resurrect.