Replaced RIOT, Other Maintenance While I Am In There?

[atari2atari]

Greetings, Atarians

 

Thanks to you all (yes, you!) I have almost successfully repaired a Sears Tele-Games six-switch console from 1978 (or late 77 – it has been “Factory Reconditioned” at least once in its life, and a mix of parts is possible?).

 

I'll tell you about it (with pictures!) and then I have a few QUESTIONS, if anyone is up for it.

 

 

(Just the shell, took this after I toredown, sorry!)

 

 

 

(Looks like someone didn't like the fact this said "Factory Reconditioned!")

 

 

 

 

(I ignored this last warning sticker, as I didn't really believe it! )

 

The sixer would initially play a game when started from COLD, about one minute in it would "reset" the cartridge, as if the console had been powered on again.

 

After the "reset" you could keep trying to play the game, but it would reset more rapidly now, and in under two minutes the display would switch to scrolling diagonal grey and black lines, and then finally a black screen. Attempts to power-cycle it with a new cartridge would only result in a black screen. On cool-down (two or three hours), it would repeat the symptoms.

 

From my reading on the forums here and the Atari service manual, it sounded like the RIOT (Ram/Input/Output/Timer) (part # CO10750) chip could be bad.

 

I scored a batch of RIOTs and a few others chips (another single RIOT, a lone TIA, and three 6507 CPUs) on eBay for under $23, shipped (yay!).

 

 

Tore down the sixer, replaced the RIOT, strung it all together on the carpet to test it, and the problem SEEMS resolved (QUESTIONS after pictures!).

 

 

(back of the "new" RIOT chip I put in)

 

 

(my handy IC inserter, which is a bit overkill, but it sure provides nice even pressure)

 

 

 

(Like my carpet? I don't! Came with the house, it's about as old as the Atari is . . . )

 

 

(my other four-switch Tele-Games off the the left there)

 

 

(Love this game cartridge - - it's the best! )

 

 

SO . . .

 

 

QUESTION 1 – was the RIOT really the issue, or is there something else that will crop back up once I bolt back together this cast-aluminum beast!

 

On teardown I noticed that the BOTTOM aluminum shielding, the thinner one under the cast bit and mainboard, had been rubbing on the mainboard:

 

 

 

 

 

I will cover up that rubpoint, likely just with thin cardboard (suggestions?), when I rebuild, but if that had REALLY been a problem, it would short things out immediately, wouldn’t it have, not the delayed response I was seeing?

 

 

QUESTION 2 – While I am in here, is there OTHER “preventative maintenance” that I should perform? I know . . . “if it ain’t broke . . .” !

 

I am not thinking of re-soldering everything, or other time-wasting, but in my reading over the last week, there are a lot of components mentioned as being “problems” or “culprits” for various issues, and so if I am here inside the machine, I wouldn’t mind getting some “good to do, if you want” preventative maintenance done.

 

Suggestions?

 

Here's a shot of the mainboard again, and then some ideas I've had continue after the picture:

 

 

I already have a right-angle power jack on order from Best Electronics, and will re-solder that new one on. The current one is “loose” and the power adapter can wiggle around in there and reset the console sometimes.

 

Got some new static strips and foam donuts for the switches from another source, too, so I will replace those as well.

 

Oh, should the ends of the static strip be attached to the cast aluminum, as they were on this unit originally? (Picture again, for reference)

 

 

That’s how it looks in the Field Manual, the ends of the strips tape to the cast shield, but just askin’ . . .

 

No hairline fractures observed in any solder I saw, so that’s good.

 

I looked for the “uncovered trace” near the J200, but am not certain which of these SHOULD be covered by the “colored dot,” or maybe this revision of mainboard has that problem etched out of it? The mainboard states “Revision B” - - is that an early one, and should I cover something here?

 

 

(near the J200, where there should be a "paper dot?")

 

 

(mainboard revision number, for your pleasure)

 

 

(switchboard revision number, also for your joy)

 

 

There were issues mentioned in some posts about the switchboard’s capacitors - - is there any utility in “freshening up” them or any of the power supply ones?

 

 

 

What about the RCA jack - - is it worth it to get a new one, maybe with gold contacts, and solder and replace the old one? I want to keep it “old school,” so no composite outputs or anything are planned.

 

 

 

So, in the end maybe there is nothing to do, but I will welcome any ideas or things you think I should look at!

 

Thanks so much, fellow enthusiasts!

 

a2a

[zylon]

The best I can show you for the colored paper dot is below. I should caution you that working on IC's and circuit boards on carpeting is a bad idea. Looks like your system was a "no-channel switch" version re-fitted later. That's fine because the channel switch switchboard was better IMO. The foil strips are supposed to contact the metal housing. I make my own from foil-tape.

[atari2atari]

The best I can show you for the colored paper dot is below. I should caution you that working on IC's and circuit boards on carpeting is a bad idea. Looks like your system was a "no-channel switch" version re-fitted later. That's fine because the channel switch switchboard was better IMO. The foil strips are supposed to contact the metal housing. I make my own from foil-tape.

 

Thank you so much for your response!

 

Yes, carpet is not an optimum work-surface - - I did all the IC replacement at the workbench, and then the final "test" I had to lay out on carpet to get close to the TV. Next time I will lay it on a board on the carpet.

 

Wow, GREAT picture of the "dot," thank you so much - - DO you think that clear nail polish would be acceptable as a substitute, or will that cause grief 5-10 years down the road? I can always just cut a square of paper and place it under the J200, too.

 

Thanks for advice on foil-attached-to-housing, too.

 

Regarding the console's "provenance" it's interesting to hear you think it was a retrofitted "no-channel switch." I am very curious about its origins. The case actually HAS a channel switch hole on the bottom, so I wonder if it was indeed retrofitted, did they replace the case, too? I wonder if the switch stickers and serial numbers at that time, too.

 

All very interesting, I hope some other people chime in with other "preventative maintenance."

 

Power regulators? Worth preemptively switching?

 

Thanks!

 

a2a

[zylon]

Clear nail polish should be fine. Your system is a Light-sixer. These were made both with channel switch and without, but all almost all have the hole for it. The Sunnyvale light 6's didn't have the switch at first, only the Dimerco(taiwan) units did. Atari used the earlier "no-ch switch" boards until stockpiles were used up. Most of the earlier units sent in were just swapped with newer parts. Based on the serial# of yours, I feel very safe in stating it was originally a no-switch unit. I have one with a later serial that doesn't have one.

Most of the voltage regulators I've had to replace were on the earlier boards, but they're cheap and easy.

Edited November 17, 2010 by zylon

[A.J. Franzman]

Re your Question 1-- you should NOT cover up the contact area you mentioned with cardboard or anything else. If you look closely, you should see that every part of the motherboard that the bottom cover of the shielding touches, is in fact part of one single circuit path- the largest one on most any circuit board, the ground. The shield is SUPPOSED to make contact with it; that's why there are lots of spots that were originally made without the green solder mask covering them, so the cover could make good electrical contact. You may be able to notice a similar arrangement on the other side of the board, where the main part of the shield touches it in certain areas.

 

The colored dot "fix" was only needed on a few of the earliest motherboards in heavy sixers, so it's unlikely that your light sixer needs it unless it had early heavy sixer guts put in it (which it does not appear so in your photos).

 

Regarding any other "preventive maintenance", other than cleaning the switches, the only things that should be done would be to install the zener diode protection on the fire button lines if that hasn't been done yet (I would think that a "Factory Reconditioned" unit should already have them), and if you're really picky, you might replace all of the electrolytic capacitors to give the console a good shot at not needing them again for 20+ years. The Zener diode fix is shown on pages 29 and 30 of the .pdf Field Service Manual, and mentioned again on the very last page.

Edited November 19, 2010 by A.J. Franzman

[atari2atari]

Re your Question 1-- you should NOT cover up the contact area you mentioned with cardboard or anything else. If you look closely, you should see that every part of the motherboard that the bottom cover of the shielding touches, is in fact part of one single circuit path- the largest one on most any circuit board, the ground. The shield is SUPPOSED to make contact with it; that's why there are lots of spots that were originally made without the green solder mask covering them, so the cover could make good electrical contact. You may be able to notice a similar arrangement on the other side of the board, where the main part of the shield touches it in certain areas.

 

The colored dot "fix" was only needed on a few of the earliest motherboards in heavy sixers, so it's unlikely that your light sixer needs it unless it had early heavy sixer guts put in it (which it does not appear so in your photos).

 

Regarding any other "preventive maintenance", other than cleaning the switches, the only things that should be done would be to install the zener diode protection on the fire button lines if that hasn't been done yet (I would think that a "Factory Reconditioned" unit should already have them), and if you're really picky, you might replace all of the electrolytic capacitors to give the console a good shot at not needing them again for 20+ years. The Zener diode fix is shown on pages 29 and 30 of the .pdf Field Service Manual, and mentioned again on the very last page.

 

THANK YOU Mr. Franzman! :-)

 

You were one of the "sources" that I had been reading last week in other posts. I appreciate you weighing in.

 

Yes, grounding - - makes sense to me! I had been staring at the board on my workbench all this week, and looking at other pictures on the Internet and thinking "maybe it's *supposed* to be that way?" I am really glad you confirmed that suspicion.

 

Yes, the Zener diodes are in place, as you guessed, probably done during its "Factory Reconditioned" visit.

 

Good call on the electrolytic caps, I may do that.

 

I am looking forward to putting this one back in the case and using it - - on the test runs after replacing the RIOT I was amazed at the color quality and crispness of the image in comparison to the 4-switch Tele-Games from just a few years later that I also have!

 

A ferrite choke or two on the video cable, and this baby will be ready for years of enjoyment. I am thrilled I found this six-switcher.

 

Thanks again for your help!

 

a2a

[svenski]

Some great and useful pics there, glad you got things sorted!

[A.J. Franzman]

Some great and useful pics there

Yes, and one of them actually shows the zener diode kludge, so my bad for not paying attention!