800xl Try to diagnose Issue (Help would be apperciated)

[Gaetznes]

I purchased this 800xl Hong Kong revision on the 16th. Lucky me, this version is all socket-ed. Unfortunately, I'm only getting a black screen with horizontal lines. Lines are white, greyish and occasionally with colours. Width and consistency of the lines vary. Pictures below

 

Things I've done in order to do some quick testing.

Verified all the logic ic's are working. I used this type of tester. http://www.pinitech.com/products/ic_tester.php

Resocketed all the ic's.

Checked the O.Crystal, 60hz, so verified its ntsc.

I've rotated the dram to see if anything different would occur. It didn't. I haven't done any piggybacking.

Double checked the power supply, all was well. Power to ic varies from 5.28v to 5.33v.

Attempted the Self-test to tell if I could at least hear the musical notes. At best I heard a single tone change in one of the test. Thought I'm assuming this was more likely the tv, not the computer. During test, image remained the same as displayed in image 1 through 3.

 

Other comments.

Sockets all look good. I have yet to re-flow, as a visual inspection revealed no cold solder joints.

Red Power light does come on

I don't own a oscilloscope

I don't own any cartridges

I haven't tested the capacitance of the capacitors yet. Though visually, their is no leaking or bludging. I own a cap wizard.

I do own a gq-4x, so replacing the basic with an eprom is an option. Once i find the pinout difference, if they exist.

 

 

So I'm curious if anyone has seen this before?

 

Images 1&2 are on lcd,

Image 3 is on a crt.

Images 4&5: two wires and a diode. I'm not familiar with the hard ware to know if this was factory or repair.

 

Removed all larger Ic's individually, to see if I could generate different images. Results

Image 6 CPU Removed

Image 7 Antic Removed

Image 8 Gtia Removed

Removal of Basic, OS, Pokey, Pia. This did not change the out put image from those of 1, 2 and 3.

 

I'm using a F connector to connect it to the tv's.

Note these lines are scrolling upwards.

 

Image 1

 

Image 2

 

Image 3

 

Image 4

 

Image 5

 

Image 6 CPU

 

Image 7 Antic

 

Image 8 Gtia

[Faicuai]

Nice!!!

 

Seems the exact same MoBo of my two Rev.C 800XL, fully aocketed. Your keyboard should be the hefty / solid ALPS keyboard, BEST ever made for the 800XL.

 

Now, if that is the case, you likely got the WORST power supply ever made (same as came with mine)... and what I see on your screen are the symptoms of a fried video-circuitry.

 

You will need to basically do two things:

 

1. DISCONTINUE use of power supply if it is the one all-black, heavy and non-serviceable (sealed).

2. Verfiy or replace 4050 chip near C50. A very likely suspect.

3. Verify trace (point-by-point) with bare MoBo and powered-up, every step on the analog output stage of video. You will have to jump Luma signal from each step on its path, directly to the video port Luma pin, until you get the troublesome pattern or it actually dissappears. In this way, you will determine any passive component (resistors or capacitors) that may have burned along the way.

 

My own experience from very similar symptons / case 800XL.

 

Cheers, and good luck!!!

[Gaetznes]

1. DISCONTINUE use of power supply if it is the one all-black, heavy and non-serviceable (sealed).

2. Verfiy or replace 4050 chip near C50. A very likely suspect.

3. Verify trace (point-by-point) with bare MoBo and powered-up, every step on the analog output stage of video. You will have to jump Luma signal from each step on its path, directly to the video port Luma pin, until you get the troublesome pattern or it actually dissappears. In this way, you will determine any passive component (resistors or capacitors) that may have burned along the way.

 

1. I didn't ever have the original power supply. Ive wired up a New DC Jack to the unit. Making sure to wire it up properly etc etc. 5.4v 2amp at the jack upon current pulled.

 

2. The tester says the 4050 ic is fine. I may order it anyways when I get the other components.

 

3. I did do a point by point continuity check, commencing on the 4050. Starting from pins 2,4,6,12, and 15. Resistor 47, 48. 49, 50 Failed. Diode CR4 has reverse leakage.

 

 

Everything else was fine from the other side of those resistors all the way to the Lum output #1

 

For the sake of the price I'm going to check continuity on other cheap passive components. Prior to my order.

 

Thank you very much for pointing me in this direction Faicuai.

 

I will update, once the parts are in and installed.

 

Edited July 18, 2017 by Gaetznes

[BillC]

5.4V is above specifications, the maximum recommended is 5.25V(5V plus or minus 5%)

[Gaetznes]

5.4V is above specifications, the maximum recommended is 5.25V(5V plus or minus 5%)

 

The voltage range, arriving at any ic is maxed out at 5.28 to 5.33v. 74 LS series logic and the hitach ram is good up to 5.5v. A quick look at the pokey data sheet does say it's maxed out at 5.25v. damage doesn't occur till at or after 9v. So I see your point. Thanks for your input.

[+DrVenkman]

Are you sure of your measurements on those resisters and the diode? That's an awful lot of passive components to fail in close physical proximity to one another.

[Faicuai]

 

1. I didn't ever have the original power supply. Ive wired up a New DC Jack to the unit. Making sure to wire it up properly etc etc. 5.4v 2amp at the jack upon current pulled.

 

2. The tester says the 4050 ic is fine. I may order it anyways when I get the other components.

 

3. I did do a point by point continuity check, commencing on the 4050. Starting from pins 2,4,6,12, and 15. Resistor 47, 48. 49, 50 Failed. Diode CR4 has reverse leakage.

 

 

Everything else was fine from the other side of those resistors all the way to the Lum output #1

 

For the sake of the price I'm going to check continuity on other cheap passive components. Prior to my order.

 

Thank you very much for pointing me in this direction Faicuai.

 

I will update, once the parts are in and installed.

 

 

Nicely done!!!

 

It is typical for those passives to go / burn, once A/C current flows at an undetermined voltage level (whereas +5DC or similar should be flowing, instead). How many damaged? Depends on exposure time, but it is clear the unit was cooked *way before* you purchased it... BUT the type of MoBo (and if it came with ALPS keyboard) is VERY WORTH rescuing.

1. If everything else seems ok, then also order small switch / interruptor and cables (as thick / practical as you can get) so you can isolate C54 from system (at will), and increase Y-signal purity substantially (will drastically reduce vertical banding on these MoBo's once Y/C output is fully enabled on monitor jack). During composite (artifacting) operation, enable C54 (per factory design), and during Y/C (s-Video) operation, disable it (optimized for s-Video). Images below, also showig good ALPS keyboard.
2. 
3. To fully enable Y/C output on your MoBo, you will also need to pick Chroma signal at terminal point before junction with Y signal (R66 / R67 junction. UNDERNEATH the MoBo), and take it straight to Chroma pin on monitor jack (small cable + soldering will be needed, but the job is extremely simple and will look pro). Peak-to-peak voltage of chroma signal (thus saturation) will be clearly higher than s-video specs., but super easily correctable in the digital domain, either with your TV's "Color" gain control, or same function on your Analog-to-Digital video processor (if you are using one).
4. The last (and major) improvement of *COMPOSITE* output (sharpness / definition) is to REMOVE (yes extract and saving in your parts bin) C56 capacitor, right of same area, as it mostly blurs the luma component. It is still not clear what is its real benefit (my take is that it *may* help reducing dc-to-dc voltage fluctuations on lowest values of luma signal, at the expense of sharpness and resolution). However, the improvement will be immediate and welcome. This is important for those titles that you want to appreciate with clarity, but rely on artifacting / composite output (there are quite a good bunch, out there).

At this point you will have ~90% (or better) of the overall video quality you can extract from this unit, with no HW intrusion and changes, and without disabling ANY OEM / factory function.

 

Cheers!

[Gaetznes]

 

Nicely done!!!

 

It is typical for those passives to go / burn, once A/C current flows at an undetermined voltage level (whereas +5DC or similar should be flowing, instead). How many damaged? Depends on exposure time, but it is clear the unit was cooked *way before* you purchased it... BUT the type of MoBo (and if it came with ALPS keyboard) is VERY WORTH rescuing.

1. If everything else seems ok, then also order small switch / interruptor and cables (as thick / practical as you can get) so you can isolate C54 from system (at will), and increase Y-signal purity substantially (will drastically reduce vertical banding on these MoBo's once Y/C output is fully enabled on monitor jack). During composite (artifacting) operation, enable C54 (per factory design), and during Y/C (s-Video) operation, disable it (optimized for s-Video). Images below, also showig good ALPS keyboard.
2. A800XL-C54_Switch-1.jpg _1D38184-web.jpg _1D38185-web.jpg
3. To fully enable Y/C output on your MoBo, you will also need to pick Chroma signal at terminal point before junction with Y signal (R66 / R67 junction. UNDERNEATH the MoBo), and take it straight to Chroma pin on monitor jack (small cable + soldering will be needed, but the job is extremely simple and will look pro). Peak-to-peak voltage of chroma signal (thus saturation) will be clearly higher than s-video specs., but super easily correctable in the digital domain, either with your TV's "Color" gain control, or same function on your Analog-to-Digital video processor (if you are using one).
4. The last (and major) improvement of *COMPOSITE* output (sharpness / definition) is to REMOVE (yes extract and saving in your parts bin) C56 capacitor, right of same area, as it mostly blurs the luma component. It is still not clear what is its real benefit (my take is that it *may* help reducing dc-to-dc voltage fluctuations on lowest values of luma signal, at the expense of sharpness and resolution). However, the improvement will be immediate and welcome. This is important for those titles that you want to appreciate with clarity, but rely on artifacting (there are quite a good bunch, out there).

At this point you will have ~90% (or better) of the overall video quality you can extract from this unit, with no HW intrusion and changes, and without disabling ANY OEM / factory function.

 

Cheers!

 

To answer your ALPS keyboard question. It does. Same as the one you pictured. Minus some of the foam.

 

Thanks for the severity and detail of your tips. I think I will try them before getting the mod board for 5200/800 http://electronicsentimentalities.com/Assembled%20Mods.html.

[+DrVenkman]

If you're going to put a mod board in it, I would be remiss to if I didn't mention Bryan's UAV board. I've got 4 of these (two Rev C's and two Rev D's) and they are fantastic. Not a shill or spokesperson, just a very satisfied buyer.

[+Stephen]

If you're going to put a mod board in it, I would be remiss to if I didn't mention Bryan's UAV board. I've got 4 of these (two Rev C's and two Rev D's) and they are fantastic. Not a shill or spokesperson, just a very satisfied buyer.

I can second this. No more hacks to original Atari circuitry, it's 100% bypassed and done properly. You will not believe how amazing the video output is.

[Faicuai]

 

To answer your ALPS keyboard question. It does. Same as the one you pictured. Minus some of the foam.

 

Thanks for the severity and detail of your tips. I think I will try them before getting the mod board for 5200/800 http://electronicsentimentalities.com/Assembled%20Mods.html.

 

NICE!

 

That's the *best* keyboard (you are lucky!). Your "rescue" 800XL is definitely a keeper!

 

Good luck!

[jum]

- Try to use AV output (not RF) , maybe the RF modulator is faulty (you can hotwire into the 5-pin monitor jack to get AV (composite) output)

- Input voltage should be between 4.9 and 5.1 V when testing (just to rule out a voltage problem)

- Do you get the disk loading sound thru the TV/monitor when you switch the 800XL on?

 

I found I needed at least a logic probe to fix the problem I had with my 800XL (faulty PIA), and the Field Service Manual and Sam's manual came in useful too.

 

Good luck with your fix.

[Kyle22]

You need to use a proper 5V supply. Not 5.4, not 5.25, but 5V! Anything over will make it run hot and cause damage.

 

5.1 is OK