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HELP, trying to fix an Atari 2600


zonaps2

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Hi,

 

I'm trying to resurrect this Atari I bought long ago and was never able to get it working,

 

When the power is on it shows black and white lines as in the video:

VIDEO:

 

I'm not very good at soldering, but I've tried these things without success:

- cleaning motherboard with contact cleaner

- remove and re inserted the 3 chips
- change voltage regulator 7805
- resolder power input
- Test another power supply (9V 500mA)
- desolder, clean and place RF modulator

 

Things I've tried with a cheap multimeter:

- 9V power supply shows 13.5V in the multimeter without being plugged in.
- when Atari is ON the voltage drops to 3.5v at the power input
- the voltage regulator shows 3.6v and 2.1v in the two 'legs', I don't know what values are the right ones.

Here there's a bunch of pics showing the tests I've done:



AWUnX3w.jpg

New power supply:
R3MhADS.jpg


1N0sldu.jpg


IWd2ymW.jpg

With Atari ON:
XE1aYeM.jpg


r7nQQCC.jpg


6zEO9If.jpg

Old regulator:
YEJXj4Y.jpg

NEw regulator:
4CbiKyX.jpg

More pics:
riXPiwq.jpg

mYHmNKU.jpg

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13 volts is fine on a unregulated supply like the Atari

 

It seems something is shorted or fried causing a short if it drops that darn low .

when powered on does anything get hot and I don't mean hunh that's seems hot but OMG that just burnt my finger frying pan hot

 

First place I would look is the regulator with your meter set to ohms measure the resistance tween the middle pin and the two outside pins it should measured 100's of thousands or even millions of ohms

 

That will kind of point you to before or after the regulator

 

PS do it while the unit is unplugged

Edited by Osgeld
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Hi Osgeld, thanks for your help!

 

I've turned on the atari for like 5 minutes but nothing gets hot, only the regulator gets warm.

 

I'm not sure if I've set my meter to the right setup, I've set it to 2000K ohms and measured first the middle leg with the top leg, then the middle leg with the bottom leg and it shows me 489 with the top leg and 004 with the bottom one,

all this with the power disconnected.

Maybe it's not the right regulator? it says L7805V and some other numbers. The guy at the electronic shop told me that's the same as the original I took it off.

 

Here are the pics:

 

FLQDELL.jpg

 

 

O7KEJsr.jpg

Edited by zonaps2
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it is (ok its got a few better ratings) the same as the one you took off

 

turn your meter down to 20K and remeasure the middle and bottom pin

 

when you measure the middle and top pin does it start off low and climb up (that big capacitor slowly charging)

 

also turn the power switch to the on position and check the resistance there

 

you should be geting 9-10(ish) volts in though that switch to the + side of that beer can cap, to pin 1 of the 7805 and 5 volts out of the 3rd pin

Edited by Osgeld
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Some of this may be covered in what you have said already but knowing an order and the exact conditions under which the measurement were taken would be helpful.

I am not sure if the power line is routed through the cartridge on the VCS as it is on the Lynx/Jaguar, therefore if it is possible to power the 2600 without a cartridge inserted make these measurements with the cartridge removed (speaking of which it has been a long time but isn’t that cartridge in the wrong way round? As I recall the main label faced the rear and the end label was the right way up).

 

With the power unit connected and VCS power switch in the off position what is the voltage on the input socket? I would expect around 12-14 volts.

 

The circuit I have shows an inductor (L204) which in the image supplied is located at one end of the 2200uF Capacitor, remove it or just one end of it from the circuit board and with the VCS power switch in the on position measure the input & output voltage of the regulator (I would have bent the regulator legs before soldering it in). If all is well I would expect around 5V out and around 12 -14 volts in.

 

If those voltages look correct re-connect L204 and remove the three IC’s, is the output voltage of the regulator still around 5 volts?

 

If the output from the regulator appears to be correct re-insert the three IC’s in turn (only one inserted at a time). Does the output of the regulator still appear to be correct and if not with which IC(s) inserted is it incorrect?

 

If the output of the regulator appears to be correct with the individual IC’s inserted measure it still correct with all three IC’s inserted?

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I've measured again:

 

Power input Atari ON:

  • no cartridge 4.2v
  • with cartridge 3.9v

 

Power input Atari OFF:

  • no cartridge 13.6v
  • with cartridge 13.6v
when you measure the middle and top pin does it start off low and climb up (that big capacitor slowly charging)

 

Yes, it does.

 

I'm not sure if I'm measuring correctly, so I'm posting pictures of what I'm doing:

 

rsP27GQ.jpg

 

6wEiXTk.jpg

 

Ec4llVb.jpg

 

vabWMdV.jpg

 

E9Ywq6b.jpg

 

sucSTKm.jpg

 

cyJSLOa.jpg

 

WkxfoGK.jpg

 

1qawrns.jpg

 

Some of this may be covered in what you have said already but knowing an order and the exact conditions under which the measurement were taken would be helpful.

I am not sure if the power line is routed through the cartridge on the VCS as it is on the Lynx/Jaguar, therefore if it is possible to power the 2600 without a cartridge inserted make these measurements with the cartridge removed (speaking of which it has been a long time but isn’t that cartridge in the wrong way round? As I recall the main label faced the rear and the end label was the right way up).

 

With the power unit connected and VCS power switch in the off position what is the voltage on the input socket? I would expect around 12-14 volts.

 

The circuit I have shows an inductor (L204) which in the image supplied is located at one end of the 2200uF Capacitor, remove it or just one end of it from the circuit board and with the VCS power switch in the on position measure the input & output voltage of the regulator (I would have bent the regulator legs before soldering it in). If all is well I would expect around 5V out and around 12 -14 volts in.

 

If those voltages look correct re-connect L204 and remove the three IC’s, is the output voltage of the regulator still around 5 volts?

 

If the output from the regulator appears to be correct re-insert the three IC’s in turn (only one inserted at a time). Does the output of the regulator still appear to be correct and if not with which IC(s) inserted is it incorrect?

 

If the output of the regulator appears to be correct with the individual IC’s inserted measure it still correct with all three IC’s inserted?

 

 

Hi Stephen, I'll try this today when I have some time. Thank you for your help!

 

EDIT:

I've went frame by frame in the above video and right when you power on the atari you can see the game, in this case Combat was inserted.

Don't know if this info is useful.

Screenshots:

 

eIdvxSz.png

 

yN6FGr9.png

 

RQGFUG7.png

Edited by zonaps2
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Some of this may be covered in what you have said already but knowing an order and the exact conditions under which the measurement were taken would be helpful.

I am not sure if the power line is routed through the cartridge on the VCS as it is on the Lynx/Jaguar, therefore if it is possible to power the 2600 without a cartridge inserted make these measurements with the cartridge removed (speaking of which it has been a long time but isn’t that cartridge in the wrong way round? As I recall the main label faced the rear and the end label was the right way up).

 

The cartridge is inserted the right way, maybe it's confusing seeing the motherboard from the rear on top of the VCS case.

 

With the power unit connected and VCS power switch in the off position what is the voltage on the input socket? I would expect around 12-14 volts.

 

Input socket with switch in the off position is 14v

 

The circuit I have shows an inductor (L204) which in the image supplied is located at one end of the 2200uF Capacitor, remove it or just one end of it from the circuit board and with the VCS power switch in the on position measure the input & output voltage of the regulator (I would have bent the regulator legs before soldering it in). If all is well I would expect around 5V out and around 12 -14 volts in.

 

Regulator Input Voltage with inductor removed is 11v

Regulator Output voltage with inductor removed is 5v

 

If those voltages look correct re-connect L204 and remove the three IC’s, is the output voltage of the regulator still around 5 volts?

 

Yes, it's 5V

 

If the output from the regulator appears to be correct re-insert the three IC’s in turn (only one inserted at a time). Does the output of the regulator still appear to be correct and if not with which IC(s) inserted is it incorrect?

 

Here are the tests:

  • only the top chip: 4.5v
  • only bottom chip: 4.9v
  • only middle chip 4.9v
  • top and middle chip: 3.2v
  • middle and bottom chips: 3.2v
  • three chips: 2.0v

I've attached a file with what are top, middle and bottom chips for me

post-14334-0-06931400-1439503864_thumb.jpg

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Try this, remove the RF cable from your TV and also from the Atari. Set your multimeter to Ohms scale and put one lead on each end of the cable. You should have virtually no resistance, if it's high (above 3 or 4 Ω) that is a problem. The cable could be shorted internally and be a factor in your corrupted video.

 

What's your reading?

Edited by atari-dna
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Try this, remove the RF cable from your TV and also from the Atari. Set your multimeter to Ohms scale and put one lead on each end of the cable. You should have virtually no resistance, if it's high (above 3 or 4 Ω) that is a problem. The cable could be shorted internally and be a factor in your corrupted video.

 

What's your reading?

 

Hi,

the cable is fine, I've used it with a NES and is working. Also I've used another cable and the problem persist. The meter shows 0.

Thank you for your help, very appreciated.

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Hi,

the cable is fine, I've used it with a NES and is working. Also I've used another cable and the problem persist. The meter shows 0.

Thank you for your help, very appreciated.

Have you tried adjusting the RF modulator? There is a slug in there you can wind in clockwise and counterclockwise directions, but do not over tighten, it should move with very little resistance. If you have a hex key about 5/32 (don't remember exactly but it is small) then you can tweak the frequency slightly and see if you can dial in your picture. If none of your chips feel hot (especially TIA) then it might be the RF is out of sync. It's a cuddly adjustment, particularly if your hex wrench is metallic, but it won't hurt to try.
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fiddling with the video output wont do jack snot if the system power is 3.2 and LESS volts, its TTL logic here folks, there is an overload and if there was a regulated power supply with a crowbar circuit on it the thing wouldnt power on at all

 

read the voltage with only the top and bottom chip (riot and tia) without the middle chip

Edited by Osgeld
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Your power adapter is a piece of crap if it measures 13.5V no load then 3.5V with the Atari turned on. You need a minimum of around 6.5V on the supply side of the regulator in order to get a stable 5V out of it. I'm using a 9V Radio Shack adapter with multiple tips cobbled on. Radio Shack stuff tends to be overpriced but it works. Regardless, if your supply adapter is dipping below 6.5V with the Atari powered on, the regulator will not be able to supply sufficient juice to power the console.

 

My frankendaptor is rated 9V, 850mA, and measures 10V no load. It has a positive polarity stereo headphone tip hacked on for Atari VCS, a negative barrel tip that works with Famicom, NES, Genesis, TG-16, and a plus tip inverted barrel for SNES. Saves wear and tear on the originals...

post-33189-0-47494000-1382588941.jpg

Edited by stardust4ever
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except the very first post in this thread states the op tried different power supplies

 

why any yutz would spend 30 bucks on a craptasic radio shack unregulated chunk of junk in the last decade, and then boast about it when any 7$ switch mode from dk or jameco would do a much better job is beyond me

 

Before you ask what causes a whole 3 volt shift which is insignificant on a unloaded transformer...

 

1)the vf of a standard issue rectifying diode 30 years ago could have been as high as 1.4 volts now they are typically 0.7 or less, assuming the worst that's a 0.7 volt difference 0.7x4 = tada! 2.8 volts

 

2) transformer design we got better and more accurate

 

3) the mains current which in the USA is a nominal 120 volt, it could be as low as 108 or as high as 130, spec says it can peak at 170 and it changes constantly of you ever log it, dumb old magnetics don't stand a chance at a perfect voltage hince the entire point of internal regulation

Edited by Osgeld
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@ Zonaps2

from then results you obtained from following my suggested tests I would conclude that...

a) There is no problem in the power stage or any short circuits across the power supply

b) Neither of the three ICs have developed in internal shot across their supply pins.

 

From the test you did combining the three IC's the middle IC which I believe would be the 6705 seems to be the common denominator when there is a problem. I noticed you did not list a reading for the combination of the top and bottom IC's only, try measuring the output of the regulator with only the middle IC removed and no cartridge inserted as before.

If you get a reading of around 5 volts I would be inclined to replace the middle IC and then see if everything checks out, if the output of the regulator is still low with only the top and bottom IC's inserted then I can only suggest using freezer spray to try and locate the problem as the components that heat up fastest will be the ones drawing the power.

If you cannot obtain freezer spray you could bag it and put it in the freezer but that take longer and is more prone to potentially shorting condensation forming as components heat up so keep something absorbent to hand.

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If one of your chips is shorted, it will be hot as f*** to the touch after a few seconds. You may try measuring between the power supply and the Atari with an ammeter (current) to figure out how much current your rig is pulling. The ammeter will need to be hooked in series between the Atari and the power supply.

 

except the very first post in this thread states the op tried different power supplies

why any yutz would spend 30 bucks on a craptasic radio shack unregulated chunk of junk in the last decade, and then boast about it when any 7$ switch mode from dk or jameco would do a much better job is beyond me

First off, it was $20, and yes, they are regulated. Grow up. I needed it ASAP and didn't feel like ordering through the mails and waiting for days.

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That 13V (unloaded, I know) is just scary considering that you can use a regulated 8/9V Adapter and ease the life of your 2600.

 

I would check:

- C205 Decoupling Capacitor;

- Diode near R203;

- 2200uF Capcitor (just swap it);
- CR201, CR202;
- C212 Decoupling Capacitor;

- C213 Diode;

- RF Module

 

If a decoupling capacitor is shorting the +5V then the lower measurements are caused by the 7805 going into limiting mode.

 

Regarding the RF Module, it is worth a try to take video straightly out of the IC.

 

 

Cheers,
Oge

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First off, it was $20, and yes, they are regulated. Grow up. I needed it ASAP and didn't feel like ordering through the mails and waiting for days.

If it was regulated your 9 volt supply the wouldn't float around ... That's the entire point of reulation

 

As to the rest of your post we know its not shorted that s why I had him check resistance in the second post

 

And we know the Atari is pulling less than an amp or else the voltage regulator would have lit up and then shut off they have internal protection

 

So if you don't mind you seem to be adding noise to this otherwise was fairly logical troubleshooting thread

Edited by Osgeld
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Hi, thank you all for your help, I really want to get this Atari working!

 

read the voltage with only the top and bottom chip (riot and tia) without the middle chip
I noticed you did not list a reading for the combination of the top and bottom IC's only, try measuring the output of the regulator with only the middle IC removed and no cartridge inserted as before.

 

Only top and bottom chip inserted measures 2.9v

 

I would check:

- C205 Decoupling Capacitor;

- Diode near R203;

- 2200uF Capcitor (just swap it);
- CR201, CR202;
- C212 Decoupling Capacitor;

- C213 Diode;

- RF Module

 

If a decoupling capacitor is shorting the +5V then the lower measurements are caused by the 7805 going into limiting mode.

 

Regarding the RF Module, it is worth a try to take video straightly out of the IC.

 

Sorry for my ignorance, but, do I have to remove the components for measuring them? Because if that's the case I could just replace them. (Assuming they are easy to get in any electronics shop).

Is it possible to measure capacitors with my cheap meter?

About the RF module, will it help with the problem if I do the A/V mod?

 

Do you have access to a logic probe?

 

No, I don't have one.

 

If you get a reading of around 5 volts I would be inclined to replace the middle IC and then see if everything checks out, if the output of the regulator is still low with only the top and bottom IC's inserted then I can only suggest using freezer spray to try and locate the problem as the components that heat up fastest will be the ones drawing the power.

If you cannot obtain freezer spray you could bag it and put it in the freezer but that take longer and is more prone to potentially shorting condensation forming as components heat up so keep something absorbent to hand.

 

As I undestand with the top and bottom chips measuring 2.9v, it means that the 3 chips are fine?

I will ask in the electronic shop if they have the freezer spray, not sure if I want to do the bag and freezer thing.

 

Thank again!!

Edited by zonaps2
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Got it working!!!!

 

I tried another power supply (the fourth one I tried), and now the Atari works.

The power supply is a 'universal' one, it output different voltages, from 1.5 to 12 volts. and says 1000mA 18w.

I put it to 9V and measured the tip and it read 15.2v

I wasn't sure if plug it or not because I thought it was too high, but I did it anyway.

 

Why does it works with this power supply and doesn't work with the other ones that are rated 9V?

Will this power supply break the atari in long term?

 

Now the image looks with a lot of noise, also the audio is not clear. what can I do to make the picture better?

I've tried 2 TV's, one LED TV and a CRT one. two different RF cables and they all look the same.

Will an A/V mod help?

 

Thanks guys!

post-14334-0-00575000-1439843751_thumb.jpg

post-14334-0-01890900-1439843756_thumb.jpg

post-14334-0-14878300-1439843762_thumb.jpg

Edited by zonaps2
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Why does it works with this power supply and doesn't work with the other ones that are rated 9V?

They should both work, maybe there is a component decaying. About measuring capacitors, it requires desoldering them so you can just swap each part with a new one.

Will this power supply break the atari in long term?

Being it an unregulated AC/DC Adapter, it would output a current near to the rated one (9/10VDC) ONLY if the written amperage is close to the actual load.

In other words, since your Atari is not going to request more than 500mA in order to work, then the input current is going to float between 12~14VDC. Which means that the 7805 will have to dissipate an incredibly higher (given the inadequate heatsink) amount of watts.

It would perpetually work at a very high temperature and, sooner or later, fail.

Now the image looks with a lot of noise, also the audio is not clear. what can I do to make the picture better?

I've tried 2 TV's, one LED TV and a CRT one. two different RF cables and they all look the same.

Will an A/V mod help?

 

The A/V modification surely helps. In that case you gain picture and audio quality by the use of a different connection and, at that point, furtherly improve the situation by the removal of the RF Modulator.

 

If you are able to replace capacitors, I suggest this as the first step to take.

 

 

Cheers,

Oge

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It's not going to damage your unit, the Atari is only going to draw 500 milliamps. Just because the Power Supply is rated at 18V doesn't mean that's what gets sent to the system, this is a theoretical maximum. Your Atari isn't going to see more than +5V (if your voltage regulator is working properly) because it (the load) is only going to demand 500 milliamps, which is going to put about 9V on the input of your voltage regulator.

 

You can check this...

 

With the unit on, and your multimeter set to DC Volts (at the lowest rating, like 20 or lower if not auto sensing) put your black lead on the regulator's middle leg (common gate) and the red lead on the output, leg 3, which is on the right side if you're looking directly at the part from the front. Output should read +5V dead on. The input leg (leg 1, opposite on the left side) should read right about 9 V if everything is functioning correctly.

 

Be CAREFUL not to short the legs with your leads as you are doing this as you will do harm to the regulator.

 

The picture could be refined by small adjustments to the RF modulator as described above, and as Oge has said, the decoupling capacitors. Possibly the styrene caps in the audio circuit also. There is an audio inductor that needs to be at the correct frequency as well, this is adjustable also, with a small hex wrench. The vertical red inductor, highlighted in your picture below. Slowly turn this and see if you can dial in good, clear audio. Your styrene caps are circled as well, they look fine though.

 

post-26843-0-94348600-1439851850_thumb.png

Edited by atari-dna
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It's not going to damage your unit, the Atari is only going to draw 500 milliamps. Just because the Power Supply is rated at 18V doesn't mean that's what gets sent to the system, this is a theoretical maximum. Your Atari isn't going to see more than +5V (if your voltage regulator is working properly) because it (the load) is only going to demand 500 milliamps, which is going to put about 9V on the input of your voltage regulator.

 

It is correct that the Atari will only draw 500mA. And that the output will still be +5VDC.

 

The problem is that on the input of the 7805 there are 14~15VDC.

 

Given the nature of linear regulators, it means that the 7805 has to transform 10V (14~15VDC minus 5VDC) into heat. You will have to dissipate around 5W. The operating temperature would be roughly 105/120°.

 

Counting that there is not a heatsink (a ground plane is used for dissipation) the 7805 is going to run too hot.

 

 

If the Adapter used by zonaps2 was regulated then the rated voltage would steadily stay 9VDC and there would be no issues. I suggest to put the switch at 7V (in that case you will come close to an output of 9/10V) :)

 

 

Cheers,

Oge

Edited by Oge
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If the Adapter used by zonaps2 was regulated then the rated voltage would steadily stay 9VDC and there would be no issues. I suggest to put the switch at 7V (in that case you will come close to an output of 9/10V)

 

I've set the power supply to 7v and works. thanks!

 

I've also made the composite video mod, and now the image is very clear!

 

Thanks everybody for the help!!

post-14334-0-99857600-1439925397_thumb.jpg

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