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mojoatomic

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Posts posted by mojoatomic

  1. Posted · Edited by mojoatomic

    It's not an IC; replace C243 (2200uf 16v or higher v rating) and C241 (.1uf 100v mylar, even if there's a ceramic disk in there) and the issue will go away. Replace C214 & C243 since your in there anyway (4.7uf 35v or better).

     

    ​You simply cannot judge the health of a capacitor by it's appearance, although I wish you could :-) Electrolytics only have a useful (in spec) lifespan of around 10 years. The .1uf mylar cap breaks down from ripple current - that's part of it's job.

    • Like 1

  2. Posted · Edited by mojoatomic

    Well, the issue is that the tube will charge without even being plugged in at all. Just light hitting the phosphor in the tube will charge it, way more than what most are prepared for.

     

    As long as you don't get near the HV side, it shouldn't be an issue. My advice is to work from the plug through rectification, ripple & step down. All of that has to be right before you go any further anyway. Rectification looks to be an issue, and it probably caused the ripple issues that caused the failure in the caps (combined with their age). Make your Wheatstone bridge with diodes rated higher than are in there now... 600v, 1000v if you want, as it won't hurt anything. Every electrolytic in the primary power supply is failing by now in any case. Up shot is that they're not expensive, nor are they hard to replace. Should be a pair of 470uf (or close to it) and some 2200uf - they'll all be about ready to pop. Don't worry if they're domed or not - just look at the diodes feeding them - they're gone. Should see some large Mylar ones as well - I'd replace those for sure. As caps are much smaller than they were in '86, you can put overrated ones in there that will occupy the same or less space than the originals. Any voltage rating is fine, as long as it's the same or more than what was originally in there.

     

    If you cherry pick the electrolytic caps in the primary to replace based on how they look, the ones you don't replace are gonna pop. The ripple needs to be tamed with new snubber caps, or they will smoke your new electrolytics quickly.

     

    It'll be a waste of time to move past the primary power supply into the horizontal until the first issue is corrected. Everything builds off the heath of the primary supply - everything, including HV starts there.

     

    I wouldn't be surprised if the waves you're seeing are just amplified ripple in the horizontal.

     

    It's possible, nay even probable that the zeeners in the primary are leaking. Do you have an oscilloscope and a curve tracer? If not, I'd just replace them. As the rest of the supply comes up to speed... weak components will find themselves.

  3. Posted · Edited by mojoatomic

    I worked on similar models. Your first issue is in the power supply, caps are leaky and need replacement. Second is heat scoring on those diodes. They're allowing a lot of ripple and reverse current and smoking the caps, which was more than likely the root cause of initial failure. Wavy lines? Horizontal or RF ripple bleed. Horizontal is separate from vertical flyback (high voltage) - if you have deflection, your HV flyback is OK. There will also be some high voltage rated mylar caps shortly after rectification - guarantee you they are bleeding and allowing ripple through.

     

    That "click" you hear when it powers off is called a "crowbar". It's a zener referencing ground kicking in a protection circuit and powering the set off. It's happening because of the failed parts I mentioned above. It will get worse and click all the time, like once every second. You will hear HV spin up and down, and then even that will stop working eventually.

     

    That's a 50KV tube, minimum - don't let it knock your balls off. They charge up to around 15-20kv just sitting in daylight (phosphor charging), and when you get across it - you will know it. They are basically huge fast discharge glass capacitors.

     

    Don't touch the HV side... but if you MUST - then before you work on the HV side... you need to discharge the tube, and DON'T solder the flyback or surrounding areas with it connected to the anode. Unplug the set. Take a well insulated screwdriver, clip a solid connection to earth ground. Stick it under the anode nipple and listen for the "pop" and arc as it discharges to ground. It's not subtle, your gonna hear it. Push the spring clip inside the anode to allow you to remove it from the tube. Leave your grounded screwdriver hanging in the hole for the tube so it won't charge up. Don't even think about plugging up the set in this state.

     

    These TV's had brilliant pictures, luminance, color separation and brightness, truly great. They achieved that in no small part by using massive flyback voltages.

     

    Don't put both hands inside the set while it's powered up, or unplugged... keep one hand in your pocket. Make sure the set is more grounded than you are.

     

    What I'm really telling you is... this isn't a toaster. Take it from a guy who repaired these for many many years. It's easy to get hurt, bad and quickly.

    • Like 4

  5. Posted · Edited by mojoatomic

    In my experience, 2600 chip failures in order of occurence are riot, Tia then cpu.

     

    I've heard the term "bit rot" applied quit a bit lately, but bit rot refers to data storage, and not IC's. Failures for IC's can be traced to age of the component - there are simply very small equivalents of circuit boards inside them, hence the term "Integrated Circuit", and external factors such as static discharge, spikes & over and under voltage conditions.

     

    You may find it very difficult to remove large IC's with an iron and something like desoldering braid without damaging the board. Get the iron HOT, and don't spend too much time in any spot. I use a vacuum station similar to this https://www.amazon.com/Aoyue-Digital-Desoldering-Station-Built/dp/B00ABJ4AEC/ref=as_li_ss_tl?ie=UTF8&qid=1485712120&sr=8-2&keywords=Desoldering+station&linkCode=ll1&tag=atariage&linkId=1b276b6006ecd56e4fdf8c524da441f6

     

    As as far as resoldering goes, touch the pin and push solder into the joint from the other side. Use a ground strap when you work on 2600's.

     

    Once you get an unsocketed IC out, solder in a socket for it. Sockets for even the 40 pins are less than 25cents

    each.

    • Like 2

  6. Posted

    My favorites, in order are:

     

    Heavy six - I just always liked working on them, I like the board layout. They are laid out to be repaired with a scope.

     

    Tele Games light six - build quality

     

    4 switch woody with ver 8 board - superb quality build and components, but I don't find them as attractive as the six switch models. I have never seen that many, production run was shorter than other versions. When one hits my bench it makes me smile :-)

    • Like 1

  15. Posted · Edited by mojoatomic

    I would also suggest you go here http://gamevaluenow.com/atari-2600 and download the price guide... Paste into excel and do a lookup table against what you have in your collection. At the least, it will give you a benchmark of what real world prices are when sold individually. I would not think you could command that number in a lot price, however. But you could get a healthy percentage with the right buyer.

     

    They also track prices for your other systems as well.

  16. Posted · Edited by mojoatomic

    Holy mackrel. Not sure where to start with that spreadsheet. It might prove difficult to source a buyer for the entire collection, might be easier to break it into systems.

     

    It's tough to sell the entire pig, so to speak. Easier to find buyers for bacon, ribs or shoulder. I'm not suggesting you should go crazy and sell sandwiches either... but you might consider all 2600 games, for example. Or all Atari, all Sega, etc.

     

    Its an an extremely extensive collection, to be sure.

  22. Posted

    Check the pins on a202 and make sure you didn't short something to a data line accidentally during your reflow rework. A data line short will not necessarily affect all games in the same way, in fact even at all. But it will cause exactly what you have described.

  23. Posted · Edited by mojoatomic

    @OP You really know your stuff. I nearly had a degree in Electrical Engineering Technology, but you seem to have practical knowledge they don't teach in school! ;-)

     

    As for the Everclear, why not pick up some SLX denatured alcohol at a hardware store? A half gallon of the SLX Denat stuff costs about the same as that tiny flask. It's also completely anhydrous unlike Everclear (95% grain alcohol) or 91% isopropyl rubbing alcohol. Just don't drink it or you'll go blind! :skull:

     

    I tried some Everclear once and I can honestly say it's probably better suited for use as a solvent or motor fuel than for human consumption... :woozy:

     

    Thanks KS, us pesky old guys and our practical knowledge :-) Truthfully though, very, very little that I learned gaining an EE translated to the way things really work. It really just gives you a reference point to begin teaching yourself. There was a phrase used... "Kick and bleed" - as in, "Nah, don't help him with that, he needs to kick and bleed, then he will understand it" - and this was the essence of training back then. Basically, there's no way to pour it all into your head, so we'll get you started but you have to have the horsepower between your ears to put the pieces together. It wasn't out of meanness, it was considered a kindness. No need to prolong the agony of a guy who wasn't going to be able to make the transition.

     

    I could show guys how to use a o-scope, I mean really, really use it... but there was no real way to make them understand what they were seeing or tell them all the ways that the data could be interpreted. The guys who couldn't quite put it all together became the ones that followed the cook book recipes of repair. You know the flow charts in the Atari Field Service Manual? That's who they're for. Anytime you see flow charts like that from any manufacturer of that era, that's who they're for. If you have an 0-scope with an octopus, variable power supply, multimeter, a good iron & schematics - flow charts just slow you down.

    • Like 2

  24. Posted

    Cool write-up. I look forward to more.

     

    How does acetone work for cleaning? And would be be willing to list the size/type, and number of each type of caps, and whatever else part wise needed for reconditioning a 2600?

    I'd be happy to list everything used :-)

     

    Say no to acetone

  25. Posted

    Only if your local hardware store sells liquor :-) - girl at the liquor store sees me in a suit and tie and says "Huh... you don't look like the type to drink Everclear"

     

    Your normal bar wouldn't have it, unless your normal bar is under a bridge near a bypass, but your local frat house would.

    • Like 1
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