DIY: Retro fitting a PicoPSU into a STf/fm/e machine

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby DarkLord » Wed Dec 26, 2012 4:24 am

That is a possibility - lowest common denominator and lowest bidder is not unheard
of. :lol:

I was off work tonight so I went ahead and changed everything. Black and white
from the power jack are connected with no breaks, and the STacy's original on/off
switch is used to control the "break" from pin#14/green wire and the ground/black
wire.

Everything seems to be working correctly. The PICO green light goes active as soon
as you plug the brick in to the power jack, and it all powers up just fine when you
turn the STacy's power switch on.

Looking good, thanks! :)
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby SoundDoctor » Wed Dec 26, 2012 1:14 pm

DarkLord wrote:That is a possibility - lowest common denominator and lowest bidder is not unheard
of. :lol:

I was off work tonight so I went ahead and changed everything. Black and white
from the power jack are connected with no breaks, and the STacy's original on/off
switch is used to control the "break" from pin#14/green wire and the ground/black
wire.

Everything seems to be working correctly. The PICO green light goes active as soon
as you plug the brick in to the power jack, and it all powers up just fine when you
turn the STacy's power switch on.

Looking good, thanks! :)


Is there an on/off switch on the brick? Bear in mind the brick will trickle standby power to the PICO in it's 'off' state, which is good if there is a use for the +5vsb inside the STacy (there isn't AFAIK unless there is a RTC chip in there that you could hack a wire to from the +5vsb to power if the battery is weak/dead) but the PICO will pull a few watts continuously in any case. Maybe useful to any Falcon or TT folk considering using a PICO ATX though. I doubt the brick will conform to the 1 watt / 0.5 watt guidelines sweeping the globe and you'll be burning watts just keeping the PSU brick warm when off. In the UK all mains power outlets have a switch on the neutral/cold side but I think this is one of the few countries in the world that has this and it's damned convenient to kill all those standby power hungry devices made in the Peoples Republic Of 'Environment? What Environment?' China. They say if we were to switch stuff 'off at the wall' we'd save 10% of our power consumption. Sorry, I sound like an eco warrior!

What I meant to say was 'enjoy the STacy!' :D
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby DarkLord » Wed Dec 26, 2012 6:02 pm

I understand.

Nothing I've had hooked up here has killed the brick. The green light on it comes
on, even when its not plugged into a jack. :(

Now the PICO itself...with the STacy's power switch wired to the positive white
wire like I had before, nothing is on (again, besides the light on the brick itself),
not the green active light on the PICO, or its orange "in use" light.

Now though, with the STacy's power switch hooked to pin#14 and ground, the
green active light does stay on, and only the orange "in use" light comes on or
goes off when you use the STacy's power switch.

Honestly, I don't think this matters though, eco/green wise because remember,
the STacy is a portable. So when I'm not actually physically using it, its stored
in a case. It'll only be plugged in when I am actually using it. For me personally
there would never be a time that the STacy was plugged in, and not in use.

So it's all good. :)
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby DarkLord » Thu Jan 10, 2013 9:33 pm

(Posted this to my PAK thread as well - but didn't people are viewing these threads,
so sorry for the redundancy)

Here we go again...

For whatever reason, when powering my setup with the PICO PSU, I get no
video on the STacy's built in LCD.

I had been doing all my testing on an external monitor, and everything works
fine there and that's why I hadn't seen this problem before.

Using the original factory power supply from the STacy, this problem doesn't
show up.

So apparently something is not coming through to the LCD when the internal
power supply is not plugged in.

It looks like some power is getting there, when I power it up, the lights for
power and the drives do come on.

Because of all the mods I've done to my STacy, I moved a 2nd PICO power supply
to a spare STacy motherboard I've got, and it does the same thing. Remove the
PICO and add the original PSU back, and the video comes on.

I also tried hooking up the PICO to both floppy drive power connectors - same
thing no matter which one it's hooked to. I also added the 2nd ground and it
made no difference (but I didn't really expect that too).

I guess I can go back to using the original PSU, but I really don't want to - the PICO
is so much smaller, more powerful, and doesn't get hot.

I'm going to look at the diagrams and see if I can figure out whatever it is that's
not making it to the LCD.

Any thoughts or suggestions are very welcome! :)
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby Poobah » Fri Jan 11, 2013 12:33 am

I'd have to check the schematics, but the lcd is going to have some power requirements beyond the normal computer... bias voltage for the LCD, inverter for driving the backlight, etc.

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby DarkLord » Fri Jan 11, 2013 2:33 am

Poobah wrote:I'd have to check the schematics, but the lcd is going to have some power requirements beyond the normal computer... bias voltage for the LCD, inverter for driving the backlight, etc.


Okay, don't have to worry about the backlight, I replaced it with an El Sheet with its own PS.

Here is a snap of the schematics:

internal PSU MB headers.jpeg


Thanks for the reply. (and Alan H. has posted some advice in my PAK thread to this as well)
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby SoundDoctor » Fri Jan 11, 2013 3:59 am

ATX delivers 3.3, 5, and +/-12v
I notice -20v in the schematic. It's entirely possible there are some regulators somewhere on the board to give other voltages. Could these be being derived from one of the weaker o/p of the pico? I know the pico only has the grunt of the 12v brick feeding it. I've seen them for sale at 60, 80, 120, and 160 watt. What is the original STacy supply rated at and does it o/p +20 / -20v or any other voltages other than 12 and 5v?

If you have a higher rated 12v brick you could try that to see if you have more luck. If the original psu does o/p a less common voltage that isn't present on the pico there are some good cheap and small trimable DC-DC regulators out there. I bought one recently that had an input range of 3v to 32v and could o/p 32v down to 1.2v and as only 1.5" x 1/2" and cost about 5 dollars. Obviously if the STacy needs an exotic voltage like 16v for part of the screen system it would be a bit of a problem as the regulator can't give a higher output than what's arriving at the input.
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby zonky900 » Mon Jan 21, 2013 11:28 pm

Have the PicoPSU been pretty stable for you since you switched it out, especially while using external devices like a floppy and/or hard drive?

The PSU in my 520STfm isn't looking so great. It makes the picture on the monitor jitter when I load a floppy from the internal drive (also electrocuted me yesterday :lol: ). This seems much more appealing to me than repairing that old PSU.

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby DarkLord » Thu Jan 24, 2013 9:18 pm

Hey gang, was searching the 'Net and found this schematic:

smps.jpg


Would it be able to take the +12v from the PICO power supply and deliver the
-20v that the STacy needs for the LCD video?

Thanks.
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby troed » Sun Aug 03, 2014 2:18 pm

Many thanks for your guide - I looked at the pictures extensively when I just did the same mod myself. (Full description with photos during the work etc will be posted once I'm done)

Regarding the discussion whether to connect 14-GND to the Atari power switch or the actual 12V input I now regret not having done the latter. The power brick I use suffers from severe high pitch squealing when the picoPSO is connected but nothing is drawing power. As soon as I flick the switch and the ST boots up the noise goes away.

One solution is to find a power brick that doesn't, of course (it's a common problem with switching PSUs), but another would be to have pin 14 always grounded and to switch on the 12V input instead.

picopsu.JPG
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby TheNameOfTheGame » Sun Aug 03, 2014 11:01 pm

troed wrote:Many thanks for your guide - I looked at the pictures extensively when I just did the same mod myself. (Full description with photos during the work etc will be posted once I'm done)

Regarding the discussion whether to connect 14-GND to the Atari power switch or the actual 12V input I now regret not having done the latter. The power brick I use suffers from severe high pitch squealing when the picoPSO is connected but nothing is drawing power. As soon as I flick the switch and the ST boots up the noise goes away.

One solution is to find a power brick that doesn't, of course (it's a common problem with switching PSUs), but another would be to have pin 14 always grounded and to switch on the 12V input instead.


Thanks for your results. Just getting ready to do this mod too. I'll consider switching the 12V instead of pin14.

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby troed » Wed Aug 06, 2014 10:06 pm

troed wrote:Full description with photos during the work etc will be posted once I'm done


Writeup now posted here: http://blog.troed.se/projects/atari-st- ... placement/

/Troed

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby TheNameOfTheGame » Wed Aug 06, 2014 10:26 pm

Very nice writeup! Thank you, I will refer back to it as I convert mine. :cheers:

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby DarkLord » Thu Aug 07, 2014 3:57 am

troed wrote:
Writeup now posted here: http://blog.troed.se/projects/atari-st- ... placement/

/Troed


Just went there and read that. Very nicely done! Bookmarked immediately. :)
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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby TheNameOfTheGame » Fri Aug 08, 2014 6:31 pm

Ok, couple questions. I'm doing this mod now but on an original ST.

So I took the power connector off and soldered in a stfm connector from spare parts I had.

The original ST has a two 5v, one +12v, one -12v input (which I checked with a meter and it is live) and 2 GNDs and one post in the middle is not connected NC. The stfm had two 5v, one +12v, and 3 GNDS. So the original st has 1 less GND and a -12v in comparison to the sftm.

Unfortunately the stfm connector has only 6 posts instead of seven, so that last GND hole is just bridged underneath with its neighbor. I hope that will be ok.

Image

Now my question is with the atx connector from the pico. There are four 5v rails on the atx and 2 on the atari. So just connect 2 atx red wires to each of the atari mainboard inputs?

I am going to break the white wire from the pico connector with the atari on/off switch and just ground pin 14 green to 13 black. But that leave 6 gnd wires from the atx. And I only have 1 post on the atari connector. How many gnd wires should I wrap together to go to the atari? All of them?

ATX CONNECTOR
Image

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby troed » Fri Aug 08, 2014 8:32 pm

TheNameOfTheGame wrote:Now my question is with the atx connector from the pico. There are four 5v rails on the atx and 2 on the atari. So just connect 2 atx red wires to each of the atari mainboard inputs?


Yes.

But that leave 6 gnd wires from the atx. And I only have 1 post on the atari connector. How many gnd wires should I wrap together to go to the atari? All of them?


Here's where my "I'm not an EE" disclaimer goes into effect. As far as I know you _should_ use at least as much wire (in square mm) for GND as you use for power - and you obviously have only one GND left but two 5V. I simply don't know whether it'll be ok anyway (and you can do with 2 or 3 wires from the ATX connector to that one pin) or whether you really should make sure you connect additional GND wires through to the ST motherboard.

/Troed

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby TheNameOfTheGame » Fri Aug 08, 2014 9:06 pm

Ok, thanks. I looked at the ST schematic over at Lonny's site and that NC post in the middle of the connector is really NC. I also tested with a meter just to make sure.

So I will route that NC post over to the other GND hole with a wire on the underside of the mainboard. That will give me 2 GND posts to work with.

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Re: DIY: Retro fitting a PicoPSU into a STf/fm/e machine

Postby TheNameOfTheGame » Thu Sep 29, 2016 9:46 am

TheNameOfTheGame wrote:Ok, couple questions. I'm doing this mod now but on an original ST.

So I took the power connector off and soldered in a stfm connector from spare parts I had.

The original ST has a two 5v, one +12v, one -12v input (which I checked with a meter and it is live) and 2 GNDs and one post in the middle is not connected NC. The stfm had two 5v, one +12v, and 3 GNDS. So the original st has 1 less GND and a -12v in comparison to the sftm.

Unfortunately the stfm connector has only 6 posts instead of seven, so that last GND hole is just bridged underneath with its neighbor. I hope that will be ok.

Image

Now my question is with the atx connector from the pico. There are four 5v rails on the atx and 2 on the atari. So just connect 2 atx red wires to each of the atari mainboard inputs?

I am going to break the white wire from the pico connector with the atari on/off switch and just ground pin 14 green to 13 black. But that leave 6 gnd wires from the atx. And I only have 1 post on the atari connector. How many gnd wires should I wrap together to go to the atari? All of them?

ATX CONNECTOR
Image



Finally got this Pico working in my old original ST:

There was a NC hole where I put little right angle header pin and soldered on the pico power connector.

Image

Broke on the white wire so the normal ST switch works to turn it on. Looped 13 and 14 on the pico of course.

Image

Came out pretty good and tested working just fine.

Image

Image

Why put a pico in an ST? First, why not? :lol: Second, I have some plans for this one for later.


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