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vitoco

Another sixer with bad video

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Part one:

 

A friend found two old 2600 light sixers which were stored together for decades. He cleaned both and powered them up unsuccessfully. He picked the best looking one and replaced the CPU with the one from the other console. As it worked, he completed the restoration with the composite A/V mod. And he lived happily ever after... The End.

 

Part two:

 

He gave me the other console, and I want to restore it. At a visual check of the boards I found nothing wrong. Electrolytic caps looked OK, but there was a bit of rust in the head of the voltage regulator screw, just like some of the other removed screws. Powering it up without a cartridge, I got a black image in the TV set. I checked the voltages at the regulator and they were OK: 9V input, 5V output. But after a moment, when I tried a cartridge with the same black screen result, I found that the voltages dropped to 2V or 3V input and 0V output. I wasn't sure if it was a capacitor or just the power connector issue, but after doing some mechanical tests (shaking the power plug to the sides), it seems that it needs to be replaced (PJ-323M).

 

As its 6507 was removed and it now had the CPU from its twin console, I replaced it with another one. I no longer had a black screen, but a jitter one:

 

fishingderby.thumb.jpg.d92ad50bc943a8da555cb557cba19501.jpg

 

I tried some other cartridges, but the result was worst:

 

defender.thumb.jpg.5f27b03c8e16608d947243e2adc826bb.jpg

 

asteroids.thumb.jpg.fb82859073221d4e10a17a16d2373102.jpg

 

(could you guess which games are them without looking the attachment names?)


I also replaced TIA and RIOT chips, and nothing changes, same results.

 

So, for the experts, what could it be?

 

I want to modify it with the composite A/V mod. Should this solve this issue?

 

Oh, another curious thing about this Rev B board is that there are two different shaped components that should be the same in C206 and C207, just like in the twin console. I also looked at many other boards in the web and I didn't find something similar:

 

c206c207.thumb.jpg.15b0cafc3b77cb390eceab450840aec7.jpg

 

As those connect to the Q202 component (transistor) that will be removed in the mod, I guess that if those are introducing the problem, it will go away at the mod, but I'm not sure.

 

Any hint?

 

Thanks!

 

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Try replacing the 4050 IC if you haven't already.

 

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Posted (edited)
20 hours ago, -^CrossBow^- said:

Try replacing the 4050 IC if you haven't already.

Thanks for the reply. I haven't try that (it is not socketed).

 

That component is A203 in the board, and it is mentioned in page 4-4 of the Field Service manual (Bad Video Troubleshooting). I tried to follow that flowchart, and at the beginning it says: "Does A203 have good Vcc (5v at pin 8 ) and ground (at pin 1)?". Measuring with a multimeter, I found that between those pins there is only 3.5V. I checked that the output of at the regulator was 5V.

 

I tried to follow the traces to find where is the fault, but moving the board a bit, the input voltage at the regulator falls from 9V to something near 3V as I said in the first post. I already ordered the PJ-323M power connector to change it as I found that this component might be the guilty. Does this make sense? Is there other component that could drop the input voltage when the board is moved?

 

Edited by vitoco
Remove smiley from pin 8) - pin 8 )

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My childhood Atari is having problems with bad video now too. I've tried everything to adjust it or fix it, short of replacing parts. My soldering skills are a bit rusty. I need to practice more before daring to try it.  In the meantime, I got a Retron 77 which is pretty cool. I love the Ranger controller! It's frankly a huge improvement over the original controllers.   One of these days, I'll get brave and try replacing parts in my original 2600. 

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21 hours ago, vitoco said:

Thanks for the reply. I haven't try that (it is not socketed).

 

That component is A203 in the board, and it is mentioned in page 4-4 of the Field Service manual (Bad Video Troubleshooting). I tried to follow that flowchart, and at the beginning it says: "Does A203 have good Vcc (5v at pin 8 ) and ground (at pin 1)?". Measuring with a multimeter, I found that between those pins there is only 3.5V. I checked that the output of at the regulator was 5V.

 

I tried to follow the traces to find where is the fault, but moving the board a bit, the input voltage at the regulator falls from 9V to something near 3V as I said in the first post. I already ordered the PJ-323M power connector to change it as I found that this component might be the guilty. Does this make sense? Is there other component that could drop the input voltage when the board is moved?

 

If moving the system around causes the voltages to fluctuate like that, then yes I would say something is loose and not making very good contact. I would start with the DC power port first and go from there. Luckily there isn't that much in the way between the DC input and the voltage regulator so if you find that the regulator isn't getting the voltage it needs or isn't putting out enough, then there isn't too much to go through to find the cause.

 

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I received and installed the power jack and the 5V seems to be stable now.

 

On 3/10/2022 at 4:17 PM, -^CrossBow^- said:

"Does A203 have good Vcc (5v at pin 8 ) and ground (at pin 1)?"

I could check that there is 5V at pin 8, but I couldn't check the ground at pin 1, because there is no direct conection from that pin to the main board ground traces. Instead, pin 1 just connects directly to R231, R232 and C238. Then, how to proceed? Or, must I just change the 4050 IC (A203) to see what happens? (I don't want to desolder and resolder too much because I'm not as good at that as I'd like to be).

 

Another question about ground: in the motherboard schematic I can see 2 grounds: logic and video, and both are connected to the 4050 IC through two of the components connected to pin 1. How can you have two grounds when there is only one from the power source? I couldn't identify in the schematic an answer to that. Then, from some starting point, are there two "parallel" ground traces?

 

Thanks!

 

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I changed the 4050 IC (A203) with one I got from a spare 800XL. The problem was solved. Thanks for the hint @-^CrossBow^-!!!

 

Then, I proceeded with the A/V mod and restored the broken case. It now works better than my original 2600 rev 13 4-switches console.

 

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