14 replies to this topic

[Leonardo Boiko]

Hi. I have an American (NTSC) 2600, with four switches. A few weeks ago it started going black and white. At first, it was b&w after turning it on, then suddenly got colors if you played for some time. A few days passed and it got b&w permanently. The color switch seems fine and spinning the color pot doesn’t do anything.

Is this a problem with defective parts? I have little experience with soldering but am willing to try to fix it, if it’s as simple as replacing a capacitor or something similar. Could anyone point me to where I can read more on this topic, or what I can do to fix the boy?

[zylon]

Try changing the voltage regulator or at least check the solder connections. I've had a couple systems do that. Could also be the little green "chicklet" near the regulator.

Attached Thumbnails

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Edited by zylon, Wed Jan 12, 2011 11:05 PM.

[Leonardo Boiko]

Thanks, much appreciated! I will try it in my coming vacations and report back if successful.

[zylon]

Hope it works for you. It's a cheap and easy enough part to try. My only other ideas would be the TIA chip or possibly RF modulator.

[A.J. Franzman]

I can't think of any way the RF modulator could fail that would cause intermittent (now permanent) loss of color. TIA chip is a good bet, if it isn't a bad connection somewhere in the color path.

[simbo]

remove the 3.579575 mhz crystal and turn it round solder in

change the 4.7uf and 2200uf electrolytics near to the regulator ic
infact all the can electrolytics ...!

sometimes the associated zener diode or other diodes and caps goes leaky{rare} to the colour control pot


watch for and replace the 2n3906 transistor associated with the crystal
i would use a bc547C type and watch the pinout it right
it has a higher gain


its unlikely the regulator is damaged as it would not work
bad solders maybe
same goes for around that crystal
i think you should look for and replace the crystal
it controls everything colour etc
and they do drift with time and atomic migration
turning it around is enough
beware for a faulty colour delay pot...!

same goes for carts and there resonators.. and crystals

Edited by simbo, Fri Jan 14, 2011 5:35 PM.

[A.J. Franzman]

simbo, on Fri Jan 14, 2011 5:18 PM, said:

remove the 3.579575 mhz crystal and turn it round solder in

change the 4.7uf and 2200uf electrolytics near to the regulator ic
infact all the can electrolytics ...!
[...]
watch for and replace the 2n3906 transistor associated with the crystal
i would use a bc547C type and watch the pinout it right
it has a higher gain
[...]
i think you should look for and replace the crystal
it controls everything colour etc
[...]
turning it around is enough
[...]
same goes for carts and there resonators.. and crystals

Man, what have you been smoking? Nothing of what you wrote, that I've quoted above, could possibly have anything to do with his unit's symptoms. If the crystal or any of its associated components are bad, the console WILL NOT WORK AT ALL, because the output from the crystal oscillator is the master clock for all of the main ICs. If a crystal is borderline in some way that causes it to have polarity, such that turning it around makes the circuit work, take that crystal back out and throw it away! Like science and belief in the supernatural, electronics and "New Age" superstitions about supposed powers of crystals do not mix. No VCS unit that I'm aware of contains a resonator (which is a module sometimes found in even older electronics, that performs the same function as a crystal).

Also, you seem to be advocating what we technicians call a "shotgun" approach. Reversing one component and replacing a bunch of others in the hope that one of them might be the bad part, is hardly the right way to go about a repair job. The first steps should be diagnosis -- testing various voltages and signals on the board to narrow down exactly where the problem lies. Only after having a reasonably sound diagnosis, should one begin the treatment phase. Sometimes the diagnostic process itself might involve replacing a component or two (especially when attempting to help an electronics novice by long-distance communication), and occasionally that replacement may in fact fix the unit. But the shotgun approach is generally far less than the optimal solution, especially considering that a novice making a bunch of component replacements could end up doing more harm than good.

simbo, on Fri Jan 14, 2011 5:18 PM, said:

sometimes the associated zener diode or other diodes and caps goes leaky{rare} to the colour control pot
[...]
its unlikely the regulator is damaged as it would not work
bad solders maybe
[...]
beware for a faulty colour delay pot...!

These are the only sensible ideas from your post, except that there's no zener diode in the color circuit (nor the crystal oscillator circuit either).

Edited by A.J. Franzman, Sat Jan 15, 2011 11:42 PM.

[simbo]

im sure he will work it out


much like you

im afraid my over 30 years in the trade counts for nothing

??

perhaps there is a magic cure wave a wand or something eh??

replace the caps turn the crystal around

last time i checked my atoms my body was made of have moved on

maybe its just the hominids dont???/

why not try some of the methods i posted ?? with resonators and crystals
on YOUR old carts and machines
instead of condem what i sayed 100%

maybe 100% of the time i am not right

but there is no need for a skaving revoke of my own experiance

i pitty you my friend as you are a true idiot

most crystals are made of inflamed quartz
that is full of impurity
why use good chip grade quarts for timing

turn it round

then tell me im daft in a somwhat nieve fashion...????

Edited by simbo, Sun Jan 16, 2011 7:28 AM.

[simbo]

simbo, on Sun Jan 16, 2011 7:24 AM, said:

im sure he will work it out


much like you

im afraid my over 30 years in the trade counts for nothing

??

perhaps there is a magic cure wave a wand or something eh??

replace the caps turn the crystal around

last time i checked my atoms my body was made of have moved on

maybe its just the hominids dont???/

why not try some of the methods i posted ?? with resonators and crystals
on YOUR old carts and machines
instead of condem what i sayed 100%

maybe 100% of the time i am not right

but there is no need for a skaving revoke of my own experiance

i pitty you my friend as you are a true idiot

most crystals are made of inflamed quartz
that is full of impurity
why use good chip grade quarts for timing

turn it round

then tell me im daft in a somewhat nieve fashion...????

[hex65000]

I'm going to bet on the color pot for this one. You can reflow the solder joints on the regulator if you like, and it won't hurt anything provided you don't create a bad joint during reflow.

As for the crystal suggestion, I'd consider that unlikely, because while it is true that crystals drift over time and temperature increases/decreases will alter even the best crystals. That said, I seriously doubt that the relatively minor changes would bork your color and have it slowly come in.

That pot going bad, will produce that behavior in my experience.

The crystal going severely out of tolerance will produce some problems -- most likely tuning related. It's more likely to pop off its mount first and then you will know it because you'll be running at zero MHz.

Hex.
[ Has a bit of practical experience himself.. ]

[simbo]

well

dont turn round the crystal then

typical ... you come here for help and when you get good advice
some novice tells the pro's how its done....

with quotes and no real evidence

i can post 1000 links easy on crystal atomic migration
and how the crystal just drift sticks to a new frequency

irratic and unpredicatable

so replace it

this maybe the only way to cure this issue

ntsc tv etc are very sensative to colour carrier changes in frequency

and no a drifted crystal will not stop the unit working
just affect its colours

moreover a faulty regulator ??? ive never seen one in over 20 years
that has some fault other than it works or it doesnt

sorry

regulators go wrong 0% unless they die
while crystals do they drift and decide to stay somewhere else
even a 2% drift as a perminent point will disolve the colour and keep the rest of the chipset in sync
its that simple...

Edited by simbo, Sun Jan 16, 2011 8:22 PM.

[snafles]

simbo, on Sun Jan 16, 2011 8:19 PM, said:

regulators go wrong 0% unless they die

I haven't been at this for 20 years, but I have seen regulators go under voltage a hand full of times.

For people that don't understand how a quartz crystal works, here's a simple explanation ...

[hex65000]

To be honest, I can't tell at this point if you are an academic, or just a troll.

Tell you what, I'll make this easy, show me five out of your 1000 meaningful links to back up what you're talking about. Especially something that backs up reversing the position of the crystal.

While I'm skeptical of the regulator being the problem, it's an easy test to make sure it's functioning correctly. The color pot? An easy test that isn't intrusive. Telling someone who admitted up front that they are not an experienced solderer yank parts willy-nilly, just sounds like a good way to have them break their system. Not to mention that they are likely to roast the can with their iron trying to get it pulled out of the board. I'm not sure you accounted for that in your supposition.

So while we wait for the OP to tell us what they have found so far, I would like to see your data.

Hex.
[ I believe the term is, "I call."... ]

[A.J. Franzman]

snafles, on Sun Jan 16, 2011 8:42 PM, said:

simbo, on Sun Jan 16, 2011 8:19 PM, said:

regulators go wrong 0% unless they die

I haven't been at this for 20 years, but I have seen regulators go under voltage a hand full of times.

I've been working with electronics for about 30 years now, and I've found regulators out of tolerance plenty of times. The 7805 is supposed to be 5.00 volts +/- 5% (4.75 to 5.25 volts), which, not coincidentally, is the same voltage and tolerance for commercial-grade TTL ICs. To this day I have never seen a 7805 output 5.00 volts or more, unless I put a resistor in its ground path to make it do so. They always seem to start below 5 volts, and drift ever lower as they age.

[Mitch]

I agree about the voltage regulator. I had a 2600 with the same issue as the original poster and replacing the vr fixed it.

Mitch