fixing an 800XL whose video just stopped working

[moffman70]

Hi all,

 

For some quick background I've been wanting a working Atari like my childhood 800 for some time, finally pulled the trigger on an 800XL on eBay a few months ago.

It a Hong Kong model in what seems to be very good condition.

Finally got everything together  - cables etc and the video worked for a few days before having serious video issues, similar to when the vertical hold on an old TV is off.

I was using the stock apparently notorious "ingot" power supply it came w at the time and won't use it anymore, replaced it with a USB adapter.

Based on some searches for similar issues I tried re-seating the Antic chip a few times, it did not seem to help and I ended up breaking one of the legs on the IC. A new one is on the way along w a GTIA just in case (assuming the chips ordered are good).

It appears to have a delay line / CO60472 replacement installed, I had to find pics of original boards to find out what this one (unlabeled) chip was.

The motherboard looks like it's in great shape no obvious corrosion etc. I plan on carefully cleaning it w some alcohol while I wait for the new ICs to arrive and give it another shot. Without video I can't tell if it's failing any other tests right now, the computer did boot to BASIC until the video issue appeared (and still appeared to be due to the screen color that was scrolling by)

Any other ideas / pointers or links to other threads?

Thanks!

 

 

[reifsnyderb]

First, I'd put a volt meter on the power supply to see if that was indeed the issue.  Try re-seating the memory as well.

[Beeblebrox]

@moffman70You have come to the right place. Every single possible issue ever experienced and fixed will be somewhere here on AA.

The great thing here is that you have a socketed machine. Makes it so much easier.  

 

A few things we need to know:

 

Is your machine a PAL or NTSC? (where are you based). 

Can you post the following images :

 

Pics of the visual issues you are seeing

Pics of the mother board/pcb

 

It could be the antic chip or possibly gtia, but also there are transistors in the video circuit which can fail causing issues like you are describing if I am not mistaken. 

 

These machines are 40 years old and anything can go at anytime. 

Edited September 25, 2023 by Beeblebrox

[moffman70]

7 hours ago, Beeblebrox said:

@moffman70You have come to the right place. Every single possible issue ever experienced and fixed will be somewhere here on AA.

The great thing here is that you have a socketed machine. Makes it so much easier.  

 

A few things we need to know:

 

Is your machine a PAL or NTSC? (where are you based). 

Can you post the following images :

 

Pics of the visual issues you are seeing

Pics of the mother board/pcb

 

It could be the antic chip or possibly gtia, but also there are transistors in the video circuit which can fail causing issues like you are describing if I am not mistaken. 

 

These machines are 40 years old and anything can go at anytime. 

NTSC

I could post some pics of the mobo later

As I broke the Antic chip I can't recreate the video issue but the BASIC blue was scrolling by a couple times a second like the vertical hold was tuned wrong

Good point about the transistors, I will test as much as I can later this week if the Antic and GTIA replacements don't help

Edited September 26, 2023 by moffman70

[Beeblebrox]

4 hours ago, moffman70 said:

NTSC

I could post some pics of the mobo later

As I broke the Antic chip I can't recreate the video issue but the BASIC blue was scrolling by a couple times a second like the vertical hold was tuned wrong

Good point about the transistors, I will test as much as I can later this week if the Antic and GTIA replacements don't help

That could be a bad transistor, 2n3904 (recalling model number from memory here). 

 

Could be antic also. Maybe check 4050 chip. 

 

I think if the delay line was dying you'd just get a black screen. 

 

One thing, can you power up the machine with audio turned up high.Do you hear anything though audio? It can tell you a lot depending on what you hear. Upload a video also if you can. Pics and videos really help here. 

 

Edit: I'd strongly recommend not putting a new antic or gtia chips in just yet. Just in case there is a voltage issue. Otherwise you can potentially fry them. Check everything else first before popping these in. Antics are hard to come by, at least over here. Ntsc ones might be more readily available. 

Edited September 26, 2023 by Beeblebrox

[moffman70]

13 hours ago, Beeblebrox said:

That could be a bad transistor, 2n3904 (recalling model number from memory here). 

 

Could be antic also. Maybe check 4050 chip. 

 

I think if the delay line was dying you'd just get a black screen. 

 

One thing, can you power up the machine with audio turned up high.Do you hear anything though audio? It can tell you a lot depending on what you hear. Upload a video also if you can. Pics and videos really help here. 

 

Edit: I'd strongly recommend not putting a new antic or gtia chips in just yet. Just in case there is a voltage issue. Otherwise you can potentially fry them. Check everything else first before popping these in. Antics are hard to come by, at least over here. Ntsc ones might be more readily available. 

Yeah I plan to check that once I get the replacement power cord in, before trying w the new chips

[moffman70]

Update the problem is actually worse now

New USB power supply came in, hooked it up, no video signal whatsoever now (before there was at least a signal though it was like a TV w broken vertical hold)

Did some quick checks w a multimeter, the voltage doesn't seem crazy off, maybe 4.75 average and nothing too high that I found, not a thorough check though

Tried installing a supposedly tested good Antic from eBay and nothing

Left it on for a good 15 minutes and checked for hot chips, the Sally is pretty warm, nothing else stands out. Not sure if that's an issue based on searches, some will say none of the chips should be warm, others say theirs is pretty hot but the computer is working 100%...

Saw somewhere that the GTIA would cause the vertical/horizontal hold issue (is this correct?), one is on order but hasn't arrived yet

 

[reifsnyderb]

Did you check the old power supply to make sure it didn't go over voltage?

 

Do you have another Sally coming?

 

Did you try booting the machine up with the audio turned up?  I'd also put in a cartridge and see if I can get any sounds out of it.

 

Can you post high resolution pictures of the system board?

 

Also, do you have an oscilloscope?

 

My usual process is to take a known good board and try each chip out, one at a time, in the known good board.  Without a known good board or an oscilloscope, this could be a lot of guesswork.

 

 

 

 

[moffman70]

2 hours ago, reifsnyderb said:

Did you check the old power supply to make sure it didn't go over voltage?

No how would I do that? Check the pins on the connector plugged in? I stopped using it as soon as I realized I had a "bad" one

2 hours ago, reifsnyderb said:

Do you have another Sally coming?

No but thinking about it, would take a week or so to get here so I just might, I see them on eBay for ~$20

2 hours ago, reifsnyderb said:

Did you try booting the machine up with the audio turned up?  I'd also put in a cartridge and see if I can get any sounds out of it.

 

 

Can you post high resolution pictures of the system board?

 

Also, do you have an oscilloscope?

 

My usual process is to take a known good board and try each chip out, one at a time, in the known good board.  Without a known good board or an oscilloscope, this could be a lot of guesswork.

 

 

No audio, I also tried holding down Option (?) and no audio

I do not have an oscilloscope nor access to a working 800XL

this worked for four or five power ons w composite video a couple of weeks ago, it booted to BASIC and I was able to run some simple programs

 

[reifsnyderb]

15 minutes ago, moffman70 said:

No how would I do that? Check the pins on the connector plugged in? I stopped using it as soon as I realized I had a "bad" one

There are two ways to do this.  This is assuming the computer is disassembled.  Turn the computer's power switch OFF and, with the power supply plugged in, check the voltage between the switch and ground.  The other way is to use the pinouts about 1/2 way down this page to check the power supply when it's plugged in.  http://www.atarimania.com/faq-atari-400-800-xl-xe-what-are-the-pinouts-for-the-various-connectors-on-the-atari_16.html

 

The reason I bring this up is that if the power supply went over voltage, we'd know that there could be a lot of damage.  If the power supply is not over voltage, the problem is probably minor.

 

Assuming the power supply never went over voltage, an option is to pull up a schematic for the 800XL and start continuity testing connections with the multi meter.  This is going to take a while.

 

 

[moffman70]

Okay, I'm an idiot..

I decided to do a thorough cleaning and reseating of everything before trying anything else and in the course of reading up on doing so realized I had put the GTIA in upside down (the marking is right side up but the actual chip orientation has the lettering upside down, at least w the one I have) and one pin on the Sally was actually not in the socket from the previous reseating attempt to fix the poor quality video

fixed those issues w the new Antic installed and it booted to BASIC (and the video looks considerably better than it did when it worked the first time) then tried a game cartridge w joystick and everything's working!

Thanks to everyone who responded, I learned quite a bit this week but it was 99% the upside down chip and Sally pin, although the new Antic looks like it improved the composite video quality substantially

[reifsnyderb]

49 minutes ago, moffman70 said:

Okay, I'm an idiot..

I decided to do a thorough cleaning and reseating of everything before trying anything else and in the course of reading up on doing so realized I had put the GTIA in upside down (the marking is right side up but the actual chip orientation has the lettering upside down, at least w the one I have) and one pin on the Sally was actually not in the socket from the previous reseating attempt to fix the poor quality video

fixed those issues w the new Antic installed and it booted to BASIC (and the video looks considerably better than it did when it worked the first time) then tried a game cartridge w joystick and everything's working!

Thanks to everyone who responded, I learned quite a bit this week but it was 99% the upside down chip and Sally pin, although the new Antic looks like it improved the composite video quality substantially

What you did wasn't uncommon.  It happens.  It's good to hear your computer is working.   🙂

 

[moffman70]

26 minutes ago, reifsnyderb said:

What you did wasn't uncommon.  It happens.  It's good to hear your computer is working.   🙂

 

Thank you

I'm guessing the Antic possibly failed or reseating the other ICs fixed the issue, the video became unusable before I ever opened the case

I did notice that the ingot power supply was putting out 6.5V on one of the pins, I don't know if that's enough to cause damage and I don't have a good setup to test each pin easily so I stopped there and won't use it again

[_The Doctor__]

6.5 V is enough to wipe any number of I.C.'s out. That boat anchor needs it's cords chopped off and sent off to the e-bin.

At least you ended up with a working machine. Good to hear.

Edited October 2, 2023 by _The Doctor__

[macsonny]

On 10/3/2023 at 7:14 AM, _The Doctor__ said:

6.5 V is enough to wipe any number of I.C.'s out. That boat anchor needs it's cords chopped off and sent off to the e-bin.

At least you ended up with a working machine. Good to hear.

Amen.