Rambo 800XL SM Version

[Overange]

Can we make it smaller?

 

Sure can

 

I redesigned the 256k RAMBO XL to have a smaller foot print, however in this design its only compatible with the 800XL model.

 

Using Myteks latest Schematic, I did away with most of the parts and functions used for the 1200XL, used surface mount Components, repositioned the PIA address line connections to be closer to the PIA. Labelling/connection IDs has not changed from the original designs.

 

Its called the RAMBO 800XL SM

 

 

Connected it up using my IC Wings on the PIA chip.

 

 

All tested last night, worked first time ( Pheww!! ), verified operation with both Atari Memory tester and Extended ram tester, tried a few different games, all seem to be very stable with it.

Left it on for nearly 24 hours running Atari Blast in demo mode.

No issues to report.

 

Sent the first build to a fellow AA member for further testing 

 

 

[reifsnyderb]

Looks great!  I am not sure how well the case will fit with the current wiring layout at the PIA chip. You may consider making up a small board to insert between the PIA chip and it's socket so as to better orient the PIA chip wires. 

[+mytek]

Excellent 👍

 

Glad to see someone taking it in a new direction. Pretty cool how all these memory upgrades have appeared recently.

[Overange]

1 hour ago, reifsnyderb said:

Looks great!  I am not sure how well the case will fit with the current wiring layout at the PIA chip. You may consider making up a small board to insert between the PIA chip and it's socket so as to better orient the PIA chip wires. 

What you see is a motherboard that is used for testing etc, it does not live in a case, so the ICwings wires are just premade male dupont ends soldered into the board.

 

However, with the little ICwings you can go inside outside which ever side you like. cut it to length to suite. Then either solder directly or use headers, the choice is yours.

 

 

[TZJB]

23 hours ago, reifsnyderb said:

Looks great!  I am not sure how well the case will fit with the current wiring layout at the PIA chip. You may consider making up a small board to insert between the PIA chip and it's socket so as to better orient the PIA chip wires. 

 

I agree, the 6520 connectors look too high to clear the keyboard once it's fitted back in the case. I am thinking it might work if you remove the 5 pins and solder the wires to the 6520 wings, but the screening can won't fit.

 

This is a good interpretation of the RamboXL, but I would prefer to see a custom 3 chip version which would make it even smaller. Normally only 3 logic chips are required in a 800XL or maybe I'm a cheapskate and don't like to waste components. 😁

 

This is my favourite from Monitor Magazine:-800XL 256K upgrade.pdf

Edited May 17, 2023 by TZJB

[reifsnyderb]

22 hours ago, Overange said:

What you see is a motherboard that is used for testing etc, it does not live in a case, so the ICwings wires are just premade male dupont ends soldered into the board.

 

However, with the little ICwings you can go inside outside which ever side you like. cut it to length to suite. Then either solder directly or use headers, the choice is yours.

 

 

I like the wings....they would work great for testing without soldering to the chips.  Personally, I'd still make up a special board, for the PIA chip, that would allow just the wires the RAMBO XL needs and running them neatly to the RAMBO XL board.  There may be room to even have a little extension so as to have the wiring already laying in the proper direction, very neatly, just for this purpose.

[reifsnyderb]

11 minutes ago, TZJB said:

 

I agree, the 6520 connectors look too high to clear the keyboard once it's fitted back in the case. I am thinking it might work if you remove the 5 pins and solder the wires to the 6520 wings, but the screening can won't fit.

 

This is a good interpretation of the RamboXL, but I would prefer to see a custom 3 chip version which would make it even smaller. Normally only 3 logic chips are required in a 800XL or maybe I'm a cheapskate and don't like to waste components. 😁

 

This is my favourite from Monitor Magazine:-800XL 256K upgrade.pdf

This one?  That could be done easily.   🙂

 

[TZJB]

Just now, reifsnyderb said:

This one?  That could be done easily.   🙂

 

 

You remembered...Yes that's the one. It's probably already small enough. The 100nF decoupler is missing though.

[reifsnyderb]

2 minutes ago, TZJB said:

 

You remembered...Yes that's the one. It's probably already small enough. The 100nF decoupler is missing though.

Ideally, shouldn't there be a 100nF decoupler per chip?

[TZJB]

Just now, reifsnyderb said:

Ideally, shouldn't there be a 100nF decoupler per chip?

 

Yes. But it worked with just the one.

[Overange]

44 minutes ago, reifsnyderb said:

I like the wings....they would work great for testing without soldering to the chips.  Personally, I'd still make up a special board, for the PIA chip, that would allow just the wires the RAMBO XL needs and running them neatly to the RAMBO XL board.  There may be room to even have a little extension so as to have the wiring already laying in the proper direction, very neatly, just for this purpose.

If I was to install this mod into my 800XL, here is an example of what could be done with minimal effort.

[Overange]

1 hour ago, TZJB said:

 

I agree, the 6520 connectors look too high to clear the keyboard once it's fitted back in the case. I am thinking it might work if you remove the 5 pins and solder the wires to the 6520 wings, but the screening can won't fit.

 

This is a good interpretation of the RamboXL, but I would prefer to see a custom 3 chip version which would make it even smaller. Normally only 3 logic chips are required in a 800XL or maybe I'm a cheapskate and don't like to waste components. 😁

 

This is my favourite from Monitor Magazine:-800XL 256K upgrade.pdf

 

I only redesigned what I am familiar with, but this could be the next 'Honey, I Shrunk the....' Project   

 

[TZJB]

25 minutes ago, Overange said:

If I was to install this mod into my 800XL, here is an example of what could be done with minimal effort.

 

That looks a lot neater and lower profile, but it depends on whether you would like the shielding can to fit. It is unlikely with two stacked sockets.

[reifsnyderb]

Since some people ( i.e. @TZJB ) are interested having a contest to see which one is the smallest, I figured I'd whip this out....

 

The through-hole version of @TZJB's 256k board, from the Monitor magazine, is 51.25mm x 30.75mm.  When converted to a SMD board, it's now 30mm x 30mm....and this is after adding 3 decoupling capacitors.   🙂

 

 

Edited May 17, 2023 by reifsnyderb

[TZJB]

15 hours ago, reifsnyderb said:

Since some people ( i.e. @TZJB ) are interested having a contest to see which one is the smallest, I figured I'd whip this out....

 

The through-hole version of @TZJB's 256k board, from the Monitor magazine, is 51.25mm x 30.75mm.  When converted to a SMD board, it's now 30mm x 30mm....and this is after adding 3 decoupling capacitors.   🙂

 

 

 

Excellent!

[reifsnyderb]

2 hours ago, TZJB said:

 

Excellent!

I just swapped out the 1206 resistors and capacitors with 0603's and the board size is now 27.25mm x 29mm.    🙂

[TZJB]

38 minutes ago, reifsnyderb said:

I just swapped out the 1206 resistors and capacitors with 0603's and the board size is now 27.25mm x 29mm.    🙂

 

Crikey, I can barely see the 1206 sized ones!

[+mytek]

20 hours ago, TZJB said:

 

That looks a lot neater and lower profile, but it depends on whether you would like the shielding can to fit. It is unlikely with two stacked sockets.

Just for people that might not know, if you have no plans to use the RF TV output the metal shielding is entirely optional. Personally I  never use RF and I always leave the RF shielding off. However if you are a fan of RF TV video, then you definitely need the shields in place, otherwise you'll see all kinds of squiggley patterns overlaying the image.

[+mytek]

21 hours ago, TZJB said:

 

Yes. But it worked with just the one.

I've even run my original Rambo XL with no decoupling caps what so ever, and saw no problems. There already appears to be enough decoupling present on the Atari motherboards to do the job without having these on the Rambo XL board as well. Of course good practice always recommends having a cap for every IC.

[_The Doctor__]

or if you like to listen to broadcast radio, or are an amateur radio operator, or if you have over the air television reception, and so on. My digital television reception pixelates more often with un-shielded equipment around and operating. It would seem the digital information is still transmitted on radio waves that can be adversely affected by such things and rather than just seeing a blip, ghost pattern etc, You loose sound and or picture to varying and even more annoying degrees. The random squares and drop outs in sound renders it unwatchable and UN-listenable.

Be a good neighbor and be good to yourself, be good to you machines, they'll last longer shielded.

[TZJB]

The RF shielding also helps to make the machine more rigid. I have noticed that the 600XL in particular has a bouncy keyboard without the rigidity of the top RF shield.

[Overange]

50 minutes ago, _The Doctor__ said:

or if you like to listen to broadcast radio, or are an amateur radio operator, or if you have over the air television reception, and so on. My digital television reception pixelates more often with un-shielded equipment around and operating. It would seem the digital information is still transmitted on radio waves that can be adversely affected by such things and rather than just seeing a blip, ghost pattern etc, You loose sound and or picture to varying and even more annoying degrees. The random squares and drop outs in sound renders it unwatchable and UN-listenable.

Be a good neighbor and be good to yourself, be good to you machines, they'll last longer shielded.

If you are really concerned with unwanted emissions and still want to have the modern mods, you can apply a coat of EMI/RFI Shielding to the inside of your case.

 

https://uk.rs-online.com/web/p/shielding-aerosols/2474251

 

 

[+mytek]

45 minutes ago, _The Doctor__ said:

or if you like to listen to broadcast radio, or are an amateur radio operator, or if you have over the air television reception, and so on. My digital television reception pixelates more often with un-shielded equipment around and operating. It would seem the digital information is still transmitted on radio waves that can be adversely affected by such things and rather than just seeing a blip, ghost pattern etc, You loose sound and or picture to varying and even more annoying degrees. The random squares and drop outs in sound renders it unwatchable and UN-listenable.

Be a good neighbor and be good to yourself, be good to you machines, they'll last longer shielded.

Hi Doc I knew you'd point this out. Although it's true that you can interfere with certain nearby radio/TV equipment, in most neighborhoods the chances are rather small (check the neighbor's roofs and backyards for antennas and towers). And if your computer equipment is disturbing your neighbors, it would be proper to try to do what you can to eliminate the interference.

 

And if your modern digital TV is disturbed by an unshielded Atari in the vicinity, then you must be using an over the air antenna to watch TV. Because in this day and age of dish, cable and streaming video I think that would be highly unlikely.

 

3 minutes ago, TZJB said:

The RF shielding also helps to make the machine more rigid. I have noticed that the 600XL in particular has a bouncy keyboard without the rigidity of the top RF shield.

I never heard this one before. So I just picked up my 600XL (without shielding) and tried to flex it -- feels pretty strong to me, although I can see that the case can be twisted with enough force applied. But realistically I doubt that has ever been an issue for anyone. And without putting my shielding back in, I can't do a proper comparison. However I would be surprised if it changed very much with the shielding in place, after all it's not exactly a structurally strong piece of thin sheet metal.

 

3 minutes ago, Overange said:

If you are really concerned with unwanted emissions and still want to have the modern mods, you can apply a coat of EMI/RFI Shielding to the inside of your case.

 

https://uk.rs-online.com/web/p/shielding-aerosols/2474251

Thanks for the link

 

I think a while back I also brought this up and provided a few US sources for something very similar. Atari ST RGB monitors used a reddish-brown color version of this.

[_The Doctor__]

Figured someone would point out the rigidity thing as well, my 130XE's creak without them, and oddly while not a 600XL, I have an 800XL that gets bouncy if it is missing the shield or the foamy rubbery support block under the keyboard. It depends on the keyboard type is my assumption.

Edited May 18, 2023 by _The Doctor__

[Overange]

3 hours ago, reifsnyderb said:

I just swapped out the 1206 resistors and capacitors with 0603's and the board size is now 27.25mm x 29mm.    🙂

So challenge accepted  

 

Double Sided Surface Mount = 20.8mm x 18.76mm

 

If I had more time, I am seeing so much more to chip away at.

 

Shame these ICs do not have a J Leg option.