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flemingt

Restoring a PAL 600xl - advice needed

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Hi everyone,

 

I'm a complete n00b and I'm looking for some advice.

 

I've dusted off my old 600xl which was a hand-me-down from my uncle back in the late 80s and decided that it would be a great project to get it back working again. Upgrade it and show it to my uncle, who's now in his 60s.

its a stock 600xl, PAL region, membrane (mylar I think) keyboard.

I've created a twitter thread here documenting my progress to date: 

So far I've given things a general clean and retro-brightened the case and that of the 1010 cassette deck.

I've checked the PSUs, 600xl is fine but the tape drive doesn't work. I've sourced one that will do the tape drive from my parts bin.

 

Everything went back together fine, hooked it up to the TV, turned it on and very surprisingly got the "ready" prompt.

 

Unfortunately the keyboard isn't working with the exception of reset, option, select, start, and break.

Thinking it was membrane oxidation, I stripped the keyboard back down and used a magic sponge to clean all the traces. I was surprised at how well that worked! I also swapped around the 2x 4051 chips and reseated C012294-19 (POKEY, I think) to see if that would make a difference. Unfortunately not, same as before only the silver buttons & break work.

 

Those keys were enough to get into the diagnostics; memory checked out ok but no sound over the antenna cable.

 

So I'm looking for a bit of guidance on where to go next. Pokey dead? I can imagine they're hard to come by these days. Some googling lead me to something called POKEYMAX. Keeping in mind that I'd like to upgrade the memory too, what options do I have?

 

Advice and guidance welcomed!

 

Thanks

 

T

 

 

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So what exactly is still the problem then?  Just that the keys on the main keyboard aren't working? 

 

Check continuity from the edges on the end of the ribbon cable to points on the keyboard membrane.  I am sure your membrane just has some opens.  

 

You can address that by either getting a new membrane,  or take a shot at repairing each open circuit using something like the copper trace paint from a rear window defroster repair kit. This has worked every single time for me at least. 

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Thanks, I'll check continuity tomorrow. Given that the sound isn't working either I suspect that it's something more.

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welcome to the forum!

hmm, sound and keyboard are handled by the pokey chip. as is the paddle controller input...

 

i had a similar sound issue a while back that turned out to be a single resistor failure:

but first its worth checking if you have sound output at the AV connector.

 

i recall having keyboard issues on a 600xl that turned out to be the edge connector socket on the motherboard side - i desoldered it and several pins fell out, already snapped. you ought to be aware that the keyboard will still work without the resistor board that goes between the ribbon and the motherboard. do you have a power LED? that is connected via the keyboard ribbon.

hope this helps!

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Yes too early to know if it's a bad pokey or mylar or something else like a bad socket under pokey, etc..  Could be oxidation too.

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Thanks for all the great info. Definitely some probing to be done with the multimeter. I don't have the big DIN av cable, just the antenna one. I'll see if I can find a pinout and wire a speaker across it. I'd a cursory look at the solder joints and pins on the connector and they seemed ok, but I will test them too.

I don't have a resistor board, the keyboard plugs straight into the logic board socket, maybe it's a version thing?

The power led makes contact with the mylar just below the help key. It lights up when the system is switched on.

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Since you are new, please be aware of the plastic cling wrap method. It can cause "blooming" and discoloration if you are not careful or leave it out too long without manipulation and massaging in the hot sun.  I just don't bother for this reason. Not worth the risks.

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Since there are all keys failing I'd bet both 4051s are not working. Those are easy and cheap to replace. 

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7 hours ago, tjlazer said:

Since you are new, please be aware of the plastic cling wrap method. It can cause "blooming" and discoloration if you are not careful or leave it out too long without manipulation and massaging in the hot sun.  I just don't bother for this reason. Not worth the risks.

Thanks for the input. It was my first time doing any kind of retro-brighting and the case was in a sorry state, so I had noting to lose. Over-the-counter hydrogen peroxide is restricted and/or expensive over here (IE) so I went with what was available. I just copied Neil from Retro Mancave.

https://twitter.com/TheRetroManCave

https://www.youtube.com/channel/UCLEoyoOKZK0idGqSc6Pi23w

He is doing a series on the 800xl which inspired me to dig my 600 out. I massaged, topped up, and realigned with the sun every 20 mins, I'm really happy with the results!

 

4 hours ago, manterola said:

Since there are all keys failing I'd bet both 4051s are not working. Those are easy and cheap to replace. 

Do the silver keys (and break) run through those chips too?

 

Now to break out the multimeter!

 

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the silver keys are handled by a different chip - the GTIA

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I've been able to check several of the keys, using the very helpful diagram and a level of dexterity trying to do 3 things at once and they seem fine.

10 hours ago, xrbrevin said:

this may be of use

600xl_7.thumb.png.9eac5a808a6e0fed3e3925b5359ead8d.png

However the contacts at the edge of the mylar look worn through. I presume it's ok to trim about 2.5 mm off?

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8 minutes ago, archeocomp said:

Can you post picture? I am really curious as I had green ribbon cable and probably different type of keyboard in my 600XL

Sure, transparent mylar membrane plugs straight into the pcb. Also, the worn leading edge.

IMG_20200810_103348.jpg

IMG_20200810_100111.jpg

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Keyboard is definitely different to mine. Your mylar end is hard to judge. Not sure if the black areas are black background or just dirt.  I would try to clean it with IPA, hard eraser gum, and maybe apply little graphite grease. But as @xrbrevin already pointed out, the connector soldered to mainboard may have broken contacts right at the solder point. It happened in my 600XL as well, at least 5 were broken

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It's actually completely transparent, the black is the background! The traces have worn through.

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I know the trim-back option works for Sinclair computers but ive never attempted it on an Atari.

maybe use conductive paint if you do not want to put it under the knife?

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I have done the trim for the mylar twice and it works. however, once I trimmed it too much and was a big mistake.. I needed to get a new mylar.. even worst: the mylar was actually ok, it was the keyboard edge connector that had problem..

So the lesson is: check the keyboard connector is doing right by using your tester in continuity mode and check in every step if everything is right... it has to be a point in which you find the problem: for example: mylar to edge connector of the mylar, then connect the mylar and check continuity with the pins of the keyboard connector, then if everything is right test with the pins of the cd4051 chip, then move to the shoulders of the cd4051 chips themselves, etc. I believe that is the only way to really know what is going on. 

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15 hours ago, manterola said:

I have done the trim for the mylar twice and it works. however, once I trimmed it too much and was a big mistake.. I needed to get a new mylar.. even worst: the mylar was actually ok, it was the keyboard edge connector that had problem..

So the lesson is: check the keyboard connector is doing right by using your tester in continuity mode and check in every step if everything is right... it has to be a point in which you find the problem: for example: mylar to edge connector of the mylar, then connect the mylar and check continuity with the pins of the keyboard connector, then if everything is right test with the pins of the cd4051 chip, then move to the shoulders of the cd4051 chips themselves, etc. I believe that is the only way to really know what is going on. 

 

22 hours ago, xrbrevin said:

if you have a multimeter, do some continuity checks at the mylar end to check if the keypress signals are getting through. if so, check again further upstream. if not, check downstream.

here is some more brainfeed material 😎

 

600xl schematic.zip 95.55 kB · 3 downloads Atari_600XL_Computer_Field_Service_Manual_Rev_1.pdf 55.85 MB · 3 downloads

Per earlier post I've checked that the keyboard presses come through for several of the keys. I've just finished continuity checking through the connector and from the connector back to the the nearest solder point / component / pass through. All good

 

I did notice a factory (I presume) bodge over by the RF modulator. Just noting this for interest.

 

Working under the assumption that the mylar trim back or replacing the 4051s will fix this aspect. I think it's time to consider upgrades before reassembling in the case and plugging the keyboard back in.

 

I know that memory is a weak spot in this system.

I also need to get a proper AV cable as opposed to using the antenna port.

 

Any recommendations on where to source these items?

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1 hour ago, flemingt said:

Any recommendations on where to source these items?

depends on your location

the atari can output composite or svideo natively. so choose an AV cable that suits your screen inputs. for DVI, HDMI, VGA you will have to install a mod.

 

for best RAM mod results, first upgrade the onboard RAM to 64k:

this will make it 100% compatible with an 800xl. then you can install mods to go beyond 64k!

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2 minutes ago, xrbrevin said:

depends on your location

the atari can output composite or svideo natively. so choose an AV cable that suits your screen inputs. for DVI, HDMI, VGA you will have to install a mod.

 

for best RAM mod results, first upgrade the onboard RAM to 64k:

this will make it 100% compatible with an 800xl. then you can install mods to go beyond 64k!

thanks,

 

PAL - Ireland.

that thread link has lead me to here:

https://lotharek.pl/productdetail.php?id=198 for an AV cable

and I could remove the RF modulator.

 

https://lotharek.pl/productdetail.php?id=291 for a 64kb upgrade

https://lotharek.pl/productdetail.php?id=56 for a subsequent upgrade. Looks like it would be a tight fit.

 

although this looks interesting too due to space constraints in the 600 chassis:

http://www.van-radecke.de/SRAM/576KB_SRAM_600XL.pdf

 

Has anyone experience with these?

 

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Ultimate 1MB I did it in a 600XL. Tight fit, but doable.

For 64KB it is super easy and super cheap (2 TMS 4464 (or equivalent) and 3 pieces of wire) AFAIK this expansion to 64kb is needed prior to Ultimate 1MB

Regarding Jurgen (http://www.van-radecke.de) 600XL expansion I think it is great, I have not use it yet, but it also replaces a bunch of logic chips (74LSxyz) and the delay line. so it is super easy and convenient if you want something simple to install and/or when the delay line of the 600XL is dead.

 

 

 

 

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