TI replacement power supply

[wierd_w]

15 minutes ago, Mehridian Sanders said:

Just as a side note, if you do go this route, you will either have to make sure that the onboard switch can handle the power inputs, or replace the switch. I know that when using 2 PSU side by side (eg: External Video Card, Thunderbolt External Enclosure, etc.) you have to shunt Pin 15 and 16 (on the main power connector) to the switch to allow it to power on and off the supply. I could be completely wrong here. Please let me know if I am misguided. ?

The connection on those pins is very low voltage, otherwise the people doing this stuff here--- would cause their jumper wire to catch fire.

 

https://www.overclockersclub.com/guides/atx_psu_startup/

 

It's a signal to the PSU to turn on. Not direct interrupt to system power. (at least on ATX supply.)

 

Intel says this about the PS_ON signal.

https://www.intel.co.jp/content/dam/www/public/us/en/documents/design-guides/resellers-power-supply-design-guide-changes.pdf

 

Quote

PS_ON# – Required

 

PS_ON# is an active-low, TTL-compatible signal that allows a motherboard to remotely control the power supply in conjunction with features such as soft on/off, Wake on LAN*, or wake-on-modem.

 

When PS_ON# is pulled to TTL low, the power supply should turn on the four main DC output rails: +12 VDC, +5 VDC, +3.3 VDC, and -12 VDC.

When PS_ON# is pulled to TTL high or open-circuited, the DC output rails should not deliver current and should be held at zero potential with respect to ground.

PS_ON# has no effect on the +5VSB output, which is always enabled whenever the AC power is present.

Table below lists PS_ON# signal characteristics.The power supply shall provide an internal pull-up to TTL high.

The power supply shall also provide de-bounce circuitry on PS_ON# to prevent it from oscillating on/off at startup when activated by a mechanical switch.

 

The DC output enable circuitry must be SELV-compliant.

The power supply shall not latch into a shutdown state when PS_ON# is driven active by pulses between 10 ms to 100 ms during the decay of the power rails.

Table 3-10: PS_ON# Signal Characteristics

Parameter                   Minimum          Maximum

VI                                                                   L0                     0.8

VIIL (VIN = 0.4 V)             -                        -1.6 mA1

VIH (IIN = 200 uA)           2.0 V                    -

VIH open circuit                 -                      -5.25

VRipple / Noise                                      400 mV p-p

 

 

 

Edited September 18, 2019 by wierd_w

[Omega-TI]

One more comment about my << Message #73 >> if  a power tap for the Jedimatt42 keyboard upgrade was included on the PCB, it would sell more of those units.  Having a standardized easy plug & play assembly standard for the community would enable more people to upgrade as some of us no longer take on soldering tasks.   Since Greg sells most everything, it would definitely make things easier for the community as a whole.

[Mehridian Sanders]

25 minutes ago, wierd_w said:

The connection on those pins is very low voltage, otherwise the people doing this stuff here--- would cause their jumper wire to catch fire.

 

https://www.overclockersclub.com/guides/atx_psu_startup/

 

It's a signal to the PSU to turn on. Not direct interrupt to system power. (at least on ATX supply.)

If I am looking at the description correctly, shunting Pin 16 and 17 to a switch. Close but no cigar Sanders

[wierd_w]

That's just a +5v DC and GND connection.  ATX has those in ample abundance. Could even be isolated from the main TI power if you wanted. Simple breakout.

[Mehridian Sanders]

Sweet! when you hook it up lemme know I am curious.

[Mehridian Sanders]

18 hours ago, wierd_w said:

That's just a +5v DC and GND connection.  ATX has those in ample abundance. Could even be isolated from the main TI power if you wanted. Simple breakout.

I relooked at what you were saying and, yeah.  If you will excuse me, I will go find the nearest steel girder for cranial readjustment. Your power line is sound.

 

 

[mcobit]

Hi,

I recently aquired a TI99/4a and had the problem with a missing external Transformator and also the internal PSU board didn't look too healthy.

 

So I came up with my own solution using mostly off the shelve parts.

 

I used a Meanwell IRM series powerbrick 12V 1.8A and etched my own replacement Board with an additional 5V Buck regulator and MAX660 in voltageinverter mode for the negative -5V Rail.

Then I replaced the old 4Pin Powerplug with a Connector from an old Deskjet Printer which fits almost perfectly.

So now I can connect it directly to the mains.

 

Works and seems to be stable and not getting too warm.

 

I also reuse the original powerswitch and LED.

 

Attached are some photos of the setup.

Edited September 27, 2019 by mcobit
Typos

[+arcadeshopper]

2 hours ago, mcobit said:

Hi,

I recently aquired a TI99/4a and had the problem with a missing external Transformator and also the internal PSU board didn't look too healthy.

 

So I came up with my own solution using mostly off the shelve parts.

 

I used a Meanwell IRM series powerbrick 12V 1.8A and etched my own replacement Board with an additional 5V Buck regulator and MAX660 in voltageinverter mode for the negative -5V Rail.

Then I replaced the old 4Pin Powerplug with a Connector from an old Deskjet Printer which fits almost perfectly.

So now I can connect it directly to the mains.

 

Works and seems to be stable and not getting too warm.

 

I also reuse the original powerswitch and LED.

 

Attached are some photos of the setup.

cool so about $20 in parts and a board you designed .. I have the original supplies in stock at arcadeshopper.com if you decide to return to stock.

 

Greg

[mcobit]

Thanks for the offer. I would need an european Powersupply (240V) anyway and also the internal one.

 

If this is stable I see no reason to change back for now. Voltage Input is universal, too for the Meanwell supply.

[Let]

I took a similar path with mcobit with some shortcut: i used Meanwell pt-45a. Added a red LED with 150ohm resistor to the additional +5v pin on the Meanwell. Prepared a small board to mount the power switch. Yes it is a tight fit and requires some cutting (see the photos).