The LaST Upgrade - Part 6 - PSU

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Re: The LaST Upgrade - Part 6 - PSU

Postby DarkLord » Fri Mar 23, 2012 6:06 pm

bid wrote:Quick question. Are there any machines that the 1.44MB mod wont work on?


When I put the 1.44 mod into my STacy, it wouldn't work with the WD1772 that was on board at the time. It was
an 02-02 chip, of which 95% of them work correctly. I had the 5% version. :roll:

bid wrote:I'm guessing that them Ajax chips are just not available anymore, so this is really neat. I wonder why no one at Atari tried this?


Actually, they are still available. Best Electronics has them - I bought one for my STacy - it was on sale at $29.95 US.

http://www.best-electronics-ca.com/custom-i.htm (scroll all the way down to the bottom of the page)

bid wrote:There is also a wire running to the YM chip of which I have no idea what purpose it is?


What pin does it go to? With Sean's mod, pin1 of the YM2149 chip can be used as a ground, and pin19
is for the DS1 line, also you can get 5v from pin40.

HTHs.
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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Fri Mar 23, 2012 6:31 pm

rebb wrote:
exxos wrote:EDIT: PSU upgrade can't hurt with other noise like the motor etc.


You are right about the hum part, cheap logitech speakers + bad cables and having old non schuko mains does not help with the problem :) Have to try isolation transformer.

Anyway ordered PSU capacitors from your page, hope it helps to get rid of rest of the audio problems (motor movement sound).


Just got the order, I'm waiting on 1 of the capacitors to come in stock, should be here monday though :) Its well worth updating them.

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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Fri Mar 23, 2012 6:33 pm

@Darklord,

Do you still have that chip ? If its "known" not to work, would be interesting to try such chips in my boards and see if they work.

That goes for anyone else really aswell, if they have any chips which work ok in 8mhz, but not 16mhz, I would love to try them out in my kits and see what happend, ive not come across many which won't work, so would be good to investigate the "why" they don't work :)

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Re: The LaST Upgrade - Part 6 - PSU

Postby DarkLord » Sat Mar 24, 2012 5:19 am

Ah sorry. :(

As I posted a bit earlier, that's the one that was replaced by the uh...traditional
snip the legs and remove routine.

Really sorry - never thought about anyone wanting to check it out. I was just
excited when the new Ajax chip worked. :)
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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Sat Mar 24, 2012 8:35 am

DarkLord wrote:Ah sorry. :(

As I posted a bit earlier, that's the one that was replaced by the uh...traditional
snip the legs and remove routine.

Really sorry - never thought about anyone wanting to check it out. I was just
excited when the new Ajax chip worked. :)


Oh yep, remember you saying that before , too many late nights etc :lol:

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Re: The LaST Upgrade - Part 6 - PSU

Postby Nikolas » Sat Mar 24, 2012 1:03 pm

At my expirience I prefer bridge rectifer that operate at 1200 volts.
Why?
When swiching st on and off it may do sparcs inside power swich and makes hier voltage then 600 volts that way it burn 600 volt bridge rectifer and blow 1 Ampere fuse.
If you guys expirience hardware problems.
1. Always remove chips if possible before soldering.
2. Resolder your hardware, check cables too.
3. If problem continue THEN must be faulty software.

I got 2 Atari ST
Main is stfm, with blitter, with 4 meg of ram, with 16mhz cpu + s-video and audio input to videobox, vdi out
P.S.
My english may not be correct

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Re: The LaST Upgrade - Part 6 - PSU

Postby rebb » Tue Apr 03, 2012 6:05 pm

Parts received and soldered! Made a difference in sound and video outputs.

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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Tue Apr 03, 2012 8:03 pm

rebb wrote:Parts received and soldered! Made a difference in sound and video outputs.


Great stuff! You may want to try feeding in a osc chip 32mhz into the shifter also. I swear that made a sharper image on my TV!

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Re: The LaST Upgrade - Part 6 - PSU

Postby rachie » Tue Jul 10, 2012 7:54 pm

exxos wrote:
krupkaj wrote:It is interesting. What about the Falcon's power supply? Does the output look similar?


My Falcon has not had all that much use, but I will suspect age will be getting the better of it.

I will price up the caps for what I used on the STFM board, was around 20quid, hard to say exactly as I ordered some other stuff, and some stuff was in packs etc, I dont mind sending people items, I order electronics stuff every week so a few more things on there isn't a problem :)



hi can u help im new on here ive got an old atari with no power pack were on earth can i get one also will it work on the new t.vs that are out today ..many thanks

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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Sat Jul 14, 2012 7:55 am

If you mean a "520ST" Then only place you will find a psu will be if someone on here has one they can sell you or evilbay. If its a 520ST/F/M/E then it does not need a external psu.

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Re: The LaST Upgrade - Part 6 - PSU

Postby Jo'ogn » Sun Jul 22, 2012 9:56 am

rebb wrote:Parts received and soldered! Made a difference in sound and video outputs.

Interesting. My 1040STfm with a 4MB extension (board from the F030 actually) has fine vertical lines on the video output. I do remember that (back in the Atari ST days around 1990) RAM extensions where said not to work properly, if wiring was just a couple of cm too long. Video output also flickers (aparently) when the Floppy servo draws current... "power without the price" does have its disadvantages - literally in respect to the PSU o_0;

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Re: The LaST Upgrade - Part 6 - PSU

Postby 1024MAK » Sun Jul 22, 2012 11:49 am

Electrolytic capacitors are well known for being the main weak point in old electronics. Even more so when used in applications like switch mode power supply units (SMPSU) like the Atari STF/STFM/STE/Falcon PSU and cathode ray tube (CRT) monitors and TV's.
Oh and don't think that your modern electronics is immune, as SMPSUs are now used everywhere... (including in your nice modern LCD monitor / TV and "Windows" computer).
The Atari STF/STFM/STE/Falcon PSU lasts fairly well. If it is has not completely died, replacing all the electrolytic capacitors, replacing the bridge rectifier, and maybe replacing the on/off switch plus re-soldering all the component pads should enable it to last for many more years of service :D

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Re: The LaST Upgrade - Part 6 - PSU

Postby Jo'ogn » Sun Jul 22, 2012 1:05 pm

1024MAK wrote:Electrolytic capacitors are well known for being the main weak point in old electronics.

Which reminds me on SMD Electrolytic capacitor leakage. Leaking acid onto the PCB and etch off conducting paths. A friend collects arcade PCB boards and went through lots of efforts to replace 'Elkos' with tantal capacitors to save his boards from potential corrosion.

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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Sun Jul 22, 2012 10:02 pm

It seems bad caps on the PSU can cause a whole host of issues on the ST. I know the first one I did the video was much brighter and sharper. Its surprising how much stuff degrades un-noticed.

I've worked on Switchmodes for years, ive had them explode over such stupid little design problems! Though the Atari one has proven to be probably one of the best PSU's out there IMHO.

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Re: The LaST Upgrade - Part 6 - PSU

Postby TheNameOfTheGame » Tue Jan 22, 2013 3:38 am

Any recommendations for a simple test fixture? I want to see how bad (or good) my old PSU is performing. Would putting some light bulbs in-line with the 5V and 12V rails give enough load to get good readings if I pull the PSU out of the case?

This is an internal PSU 120V version.

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Re: The LaST Upgrade - Part 6 - PSU

Postby zonky900 » Tue Jan 22, 2013 4:54 am

Jo'ogn wrote:Video output also flickers (aparently) when the Floppy servo draws current... "power without the price" does have its disadvantages - literally in respect to the PSU o_0;


Yup - I'm experiencing this right now with my 520STfm.

TheNameOfTheGame wrote:Any recommendations for a simple test fixture? I want to see how bad (or good) my old PSU is performing. Would putting some light bulbs in-line with the 5V and 12V rails give enough load to get good readings if I pull the PSU out of the case?

This is an internal PSU 120V version.


You don't have a multimeter you could use for this?

exxos, have you any experience with the PicoPSU mod? I'm looking to service my STfm's PSU as soon as I can because not only is it on its very last legs but I wasn't really convinced the PicoPSU was worth all the extra hassle (well, except that the Atari PSU electrocuted me the other day, but I'm the only one to blame for that :lol: )

Very nice guide though, the pictures are great and very helpful. Just repaired a few power supplies in some old amps recently and ready to tear apart the STfm again!

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Re: The LaST Upgrade - Part 6 - PSU

Postby TheNameOfTheGame » Tue Jan 22, 2013 5:41 pm

Oh yea I have a meter and all that. But I had already taken apart the ste to resolder the joystick ports and noticed the psu is in sorry shape. I took it out and found some darkened areas and flaking resistors. So I don't want to put it back in until it is checked and/or refreshed.

Anyway, I have an old C64 tester somewhere with some 12V bulbs. I'll just adapt it for now.

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Re: The LaST Upgrade - Part 6 - PSU

Postby DarkLord » Tue Jan 22, 2013 9:58 pm

I'm personally very satisfied with the PICO power supply, at least the 2 models
I've got.

You will have to adapt it to your particular Atari model, but there are message
threads here, and at Atari Forum, with pictures to help.

It runs cooler, gives more stable power, smaller in size, and it "future proofs" your
Atari's PS needs. What's not to like? :)

http://www.atariage.com/forums/topic/19 ... e-machine/

viewtopic.php?t=23488
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Re: The LaST Upgrade - Part 6 - PSU

Postby zonky900 » Wed Jan 23, 2013 7:11 am

DarkLord wrote:I'm personally very satisfied with the PICO power supply, at least the 2 models
I've got.

You will have to adapt it to your particular Atari model, but there are message
threads here, and at Atari Forum, with pictures to help.

It runs cooler, gives more stable power, smaller in size, and it "future proofs" your
Atari's PS needs. What's not to like? :)

http://www.atariage.com/forums/topic/19 ... e-machine/

viewtopic.php?t=23488


Yeah, I was going through those threads. Just couldn't decide whether I wanted to repair my STfm's PSU or replace it with a Pico.

The PSU in mine is pretty gross looking and I'm worried that repairing it might actually not end up being that much more cost effective than switching it out with a Pico! Although, since you have a few different ones in your machines already, sounds pretty good, I can take your word for it :mrgreen: :cheers:

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Re: The LaST Upgrade - Part 6 - PSU

Postby DarkLord » Wed Jan 23, 2013 2:36 pm

Not just me either - quite a few other people here and at AtariAge have
used the PICO for things.

I can't remember any bad opinions about them.
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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Thu Jan 24, 2013 10:15 am

In general you shouldnt just test a switchmode with a meter, some of them need a load to function correctly. I can't remember off the top off my head if the ST PSU's turn off with no load or not, but I would suggest loading them with a lamp or load resistor which will pull 50% of its rated output wattage.

As for the pic psu, I was looking into them a long time ago to power my 060 falcon. Though I have read people have had problems with them. I did talk to the guy who makes them, though I don't know enough about the thing still to clear up some confusion. Bascially when I explained this "problem" he said "its not how they work" though he did not explain "how they work" either, Which I can understand, but without having one to test here myself to see exactly the input and outputs i can't form my own conclusions.

The problem was, the total psu current needed to powe the CT60 was about 60watts, so the guy was saying a 60 watt mains adapter is fine. Though the problem I have with that, is the amps output to the CT60 needs to push around 8 amps just to power the cpu. Now if the picopsu is a stright switchmode design to switch 12V to 3.3V then you need 12volt 8amps psu at least which is 96watts, plus more wattage needed for the 12V 5V rails etc. 8amps at 3.3V is around 30watts, but 30 watts at 12 volt input is 2.5amps. In that respect its simple match that you simply cannot get 8amps from a 2.5 amp source kinda thing. The only way it could work is if the pic psu had a step down transformer which would step down 12V to 6V, this would double the current to 5amps (in reality less due to losses) but even so, less than 5 amps is still a long way off 8amps, and thats not including the other voltages. At that point i just gave up looking into the thing. Maybe someone who has more experience in the thing can clear up these figures...

Its possible the 160watt version would be the best choice, but to me, even that would fall sort to power the CT60. Though people do use the smaller versions and they do work. I can only think that the smaller wattage versions work but not under full cpu load. I think the 160watt version had 6amp output on the 3.3volt rail, so even that alone falls short of 8amps rated for the CT60. Not to mention guys who want to overclock which will pull more current.

So unless theres a way to pull 8amps 3.3volt from a 12v 2amp source which I have overlooked in switchmode design at some point, I can't see them being reliable. Even if they had a step down transformer it would still fall short of rated output current. Maybe they are not taking into account a full constant DC load on the output ? When I design my switchmodes and inverters I always make sure they can sustain rated output currents. Its possible its 2amps RMS output, and 6amps peek. Maybe enough for some applications, but I can't see it being able to sustain a constant 6amps from a 2amp input. I would like to know anyone who can verify this though. I think it would be a good test for a lot of people to know what the thing is really capable of.

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Re: The LaST Upgrade - Part 6 - PSU

Postby DarkLord » Thu Jan 24, 2013 12:16 pm

Well, I never tried it on my CT60 powered Falcon. I've got a standard ATX PSU
there, and I never thought about replacing it with a PICO. (keep in mind, I
re-cased that though)

As far as my STacy goes though, I've not had any problems with the 120w PICO
powering it. It's powering the STacy motherboard, EL sheet and its converter
PS, PAK accelerator board with a 68030 and 68882, internal Ultrasatan, etc,...

I've ran test programs on it, played games on it, let it set and run for hours,
and so far no problems.

Maybe the requirements for the ST, including the STacy (even with the mods
I've done) aren't as high as the Falcon with a CT60 I guess.
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Re: The LaST Upgrade - Part 6 - PSU

Postby troed » Thu Jan 24, 2013 12:28 pm

DarkLord wrote:Maybe the requirements for the ST, including the STacy (even with the mods
I've done) aren't as high as the Falcon with a CT60 I guess.


I've recently purchased an 80W picoPSU (although not installed it yet). I did so after having read that the ST PSU was rated at 35W and the actual consumption lower than that - hopefully giving me a lot of leeway.

viewtopic.php?f=15&t=19700#p171301

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Re: The LaST Upgrade - Part 6 - PSU

Postby exxos » Thu Jan 24, 2013 6:46 pm

@ Darklord - 120W should be fine for the stacy. Though what psu do you have powering the pico ?

@troed.. Maybe you could test your 80watt thing before you install it ? You would need something along the lines of a 1ohm resistor 10watts or so and connect to the 3.3V rail. This will give 3.3amps at about 11watts. Knowing the output wattage, if you could measure the DC input requirement with a meter, or power with a desktop psu which shows current, then we can see how much current is really passing between input and output. I suspect 4amps will be pulled from 12volts to sustain the 3.3V output. Though I also think the pico psu would become very hot even though its only supplying 10watts out of the "rated" 80watts.

If it draws from the 12V rail less than 3 amps, then the thing has to have step down transformers. Its hard to tell from the images exactly what the parts are. Even so, I still doubt 80watts at full load. Not saying it can't be done.....

I have been working solid in inverter efficiency the past couple of weeks, Very hard to get 89% efficiency at 8amps load, my inverter does this with no heat, but its using 2.6mm dia inductor wire to keep resistance down. anything smaller and those fractions of a watt build up very fast in heat. This is a constant "burn" not just "intermittent" loading (would be more like 97% efficiency). I just have this feeling it will just go "pfft" at full 80watts load in under 60 seconds..

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Re: The LaST Upgrade - Part 6 - PSU

Postby DarkLord » Thu Jan 24, 2013 7:55 pm

Model 1206, output 12v, 6 amp is what I'm using at the moment. Seems to do fine.

I'm really looking for a 20v model so I can try to get a -20v to use on the STacy's LCD
input. Tough.
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