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From the start of the aluminium box there was one design criteria: no mains voltage within the case! And so it should remain when building the new TI-99/4max console. But this time, the origin was not the modified original power supply, which has been pimped with some fat caps, diodes and passive cooling. | |||
| So, I cannibalized three of the common switching power supplies, which you find laying around everywhere, and put them into the PEB. Comprehensive filtering of the current was considered lower priority, but until now, the prototype works flawlessly. The 5V train delivers 5A, the 12V supply provides 3A max, and the -5V are taken from an old ZIP drive power supply, whose +5V terminal goes to ground. The 1A it may deliver are far beyond any need, but what the heck... These three voltages are present immediately after plugging in the PEB, so the PEB needs not to be switched on for the console to work. They are mounted in a way, so that the airflow is not disturbed significantly, and they are mounted on an acrylic plate, one-sided covered with aluminium adhesive tape, and screwed to the long screws of the transformator. |
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The fan is (or: was) a Papst 8412 GMV, that featured a speed control using a NTC, which allows it to run with low speed if the PEB is off, and then to go to high speed when it is switched on. To achive this, a small PCB was installed on the original PCB, from where I can get the 12V when the PEB is on. These 12V control a reed relay, which switches the control line of the fan to ground, thus putting it to max speed. ... or, it was planned to be that way. But the 8412 GMV had a very bad bearing, making it more noisy than the original fan (anyone considered this possible?). New GMV types are no more obtainable, the Noctua types are a bit low on airflow, and other "Low Noise" fans do it even worse. So, as an interim solution, an old 8412L was digged out from the vaults and connected to a special plug I already built in as "plan B"... - done (I thought...). |
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| The connection to the console is made by 7 pin plug on the rear of the PEB, where also 2 pins for the 24V AC needed for the (really!) silent fan were available - for this, a small transformer is provided. |  | ||
| All switching power supplies are connected by this PCB, on their primary as well as on their secondary side. |
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| Contact: {anyname}@{use_the_url}.net |
All pictures on this whole website were made by myself. Should you find them elsewhere, they're stolen from here! |
Last updated: 2025-09-22 CW |