- The LaST Upgrade -
PART 20 - EXXOS PSU 2015 EDITION
exxos 2015 - Last updated March 2, 2023
EXXOS PSU FITTING |
Firstly you need to get some tools. Basic stuff really. Soldering iron, solder, side cutters, 3BA nut spinner (or pointed nose pliers) Phillips 1P & 2P (cross head) screw driver, IPA swabs, drill with 3mm drill bit, heat transfer paste, scribble stick. Medical plasters are useful if your prone to cutting yourself on metalwork. I strongly recommend Arctic Silver 5 paste and I really wouldn't bother even trying to use anything else. I have personally tried and tested MANY pastes over the past 10 years and the AS5 is a long term reliable product with great heat transfer properties. So here goes.. Firstly you need to remove your old PCB board from its metal chasis and cut off the 2 mains wires to the PCB. Once removed there is normally a plastic sheet glued on top of the metal base (as was under the PCB) this needs to be removed. Also there is normally a plastic "hood" over the mains switch which needs to be removed also. Take the 2 screws out of the switch. So you should have something looking like this... |
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Next screw the new PCB onto the metal base (it fits in the same holes as the old PCB). Don't tighten up fully as the PCB will be removed again shortly.. NOTE - because of so many variations of metal base, some people may find the holes do not align perfectly. But it is still possible to screw all 4 holes with a little effort. It just a "tight fit". Take your favorite scribble stick and mark out the regulator hole as shown below. MAKE SURE THE REGULATOR IS LAY PERFECTLY FLAT AGAINST THE METAL BASE BEFORE DRAWING THE HOLE. UPDATE- If you have the Falcon PSU version then you need to also drill holes for the second regulator.
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At this point double check nothing on the solder side of the PCB is touching the metalwork. Simply look at the edge of the PSU PCB and see if anything is touching or close. While generally I do check this, please double check and trim any wires if necessary. Now remove the PCB then drill a 3mm hole where you marked for the regulator. Make sure you have no burrs either side of the metalwork. File off is necessary. Note - The other regulator is the 12V one and does align fully with the metalwork :( Thankfully the 12V regulator doesn't get warm even under a 1amp load so it is not necessary to bolt it to the base. Clean the highlighted areas in the image blow with IPA cleaner or IPA swabs.
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Once cleaned, apply the AS5 paste as shown around the drilled hole. Note- As the metalwork is used as a additional GND connection for the PSU board, I would recommend using anticorrosion paste as sold in my store. This will prevent the air from getting to the contacts and stop them from corroding or oxidizing. The paste will improve conductivity long term also.
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Screw the new PCB back into place loosely and push the bolt though the bottom side of the PSU, place the waster on top then the nut and tighten up along with the 4 PCB mounting bolts. NOTE - On older style boards where the ROMs are under the PSU in sockets, the screw will touch the top of one of the ROM's. If this is the case, then the ROM must be taken out of its socket and soldered into the motherboard. Next up is to solder the PSU to the switch. Now there are 2 ways. Either reuse the original switch (yuck!) or if you purchased a new switch from my store (yay!) , then follow that set of instructions. Both methods are listed blow.
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OLD SWITCH WIRING
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Pretty straight forward. I would suggest the switch wires be resoldered so they are traveling to the right. Otherwise the PSU switch solder tabs may touch the PCB and that would be bad! |
NEW SWITCH WIRING 230V
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Cut off the yucky old switch (cut wires close to the switch) , and burn it while videoing it then upload it to youtube. Smashing it with a large hammer is also acceptable. Reuse the old bolts and put on the 3mm nuts as shown in the image above.
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The blue wire (neutral) on the transformer goes to the neutral (white wire) on the mains socket. The black wire (live) goes to the switch as shown. Then the brown wite of the transformer (live) also goes to the switch as shown. |
110V SWITCH WIRING
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Photos submitted David Kimberlin-Wyer The 110V transformer wiring is slightly different than the 230V one, but very similar. While the 230V transformer wires have BLUE and BROWN wires, the 110V has the same wires but paired with GREY and PURPLE. These are generally twisted together when I ship them, and should be wired as shown in the above image.
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MOTHERBOARD CONNECTION
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Cut off the old PSU power connector and solder it onto the new PSU as shown. All sorted :) I would suggest the PSU be tried externally (out of the ST) to ensure everything is well before powering up your ST. The PSU will show approximately 5.05V off load and 12.05V off load. When fitting the new PSU, the PSU metal cover will most likely need to be left off as there is no room left height wise to fit it. Also if you are fitting your own transformer in particular, all wires should be kept as short and as low down as possible. Otherwise the transformer wires may push up on the Atari case plastic.
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