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Motherboard Voltage Taps


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Is there a list anywhere of convenient place to connect voltage taps to run the various mods we can now install and enjoy? I have found limited references for the 130XE, but nothing for the 800XL much less the older machines

 

Short of going around with a multimeter and testing the ends of resistors and the like it feels a bit hit and miss. One of the best ways I have found is to tap the back ends of the various sockets like SIO and the Joystick port. However, not only do the useful ones like +5V and GND often seem to be hidden on the inner row of pins, but I worry I might be introducing interference and RF noise - especially in the case of input/output.

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Is there a list anywhere of convenient place to connect voltage taps to run the various mods we can now install and enjoy?

 

Search AtariAge - there are threads for help with just about every common mod out there, and high-res scans of schematics for just about everything are available as well.

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Search AtariAge - there are threads for help with just about every common mod out there, and high-res scans of schematics for just about everything are available as well.

 

Certainly sound advice!

 

I just wondered if there was an official Atari schematic - or collection of schematics for the different machines - available anywhere that I had not come across.

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Is there a list anywhere of convenient place to connect voltage taps to run the various mods we can now install and enjoy? I have found limited references for the 130XE, but nothing for the 800XL much less the older machines

 

Short of going around with a multimeter and testing the ends of resistors and the like it feels a bit hit and miss. One of the best ways I have found is to tap the back ends of the various sockets like SIO and the Joystick port. However, not only do the useful ones like +5V and GND often seem to be hidden on the inner row of pins, but I worry I might be introducing interference and RF noise - especially in the case of input/output.

Sam's Computerfacts 800XL and the 800XL Field Service Manual have schematics that show all the resistors, capacitors, chip pins, everything. VCC labeled points should

be good for the +5V source. I just go to the +5V connector of the power jack. There are lots of VCC. The Sam's and 800XL FSM are available in pdf form at atarimania.

You can send those to a printer.

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Sam's Computerfacts 800XL and the 800XL Field Service Manual have schematics that show all the resistors, capacitors, chip pins, everything. VCC labeled points should

be good for the +5V source. I just go to the +5V connector of the power jack. There are lots of VCC. The Sam's and 800XL FSM are available in pdf form at atarimania.

You can send those to a printer.

 

Excellent!!! That is exactly what I was after russg. Many thanks!!!

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+5 and ground are easy. Each are on either side of all those little decoupling capacitors all over the board. Ground is all over the board at the edges where the shielding touches it. Look at the schematic for the Vcc pin on the chips, then follow the trace on the board. That will lead to a +5 point.

 

Common sense, good eyes, and possibly a multimeter and schematic are all you need.

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Sam's Computerfacts 800XL and the 800XL Field Service Manual have schematics that show all the resistors, capacitors, chip pins, everything. VCC labeled points should

be good for the +5V source. I just go to the +5V connector of the power jack. There are lots of VCC. The Sam's and 800XL FSM are available in pdf form at atarimania.

You can send those to a printer.

Here's pdfs of Sam's 800XL component locations and names and a grid of the mb. and a pic of the chips on the mb.

If you have the Sam's 800XL computer fact, that's where they come from.

800XLSamslocations.zip

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