Help with picoatx on amiga1200 board: the screen goes on and off

[superfrog76]

Greetings

got my picoatx and modded it to go in my custom case project (posted here on the board in another section); all right, except that I am having issues with the output.

I use a HDMI/Scart converter for the output to a LCD monitor; works nicely and allows me to use the amiga on my lcd at 1080p (altho the resolution is not really hd, but who cares...I need something that works also on ndos games, so the indivision is not an option, also because it cost too much).

You may know the adapter; it is the alternative to the GBS-8220, which I also have and was not able to use it consistently. It basically gets the scart output from the amiga, and convert it to hdmi output, which goes to my monitor.

Now, when I connect the pico power to the HDMI converter, floppy and amiga, when I power it, I get the screen on, but then it goes off, like if it would loose the sync, and then on again; every few seconds. The image is clear, but it last few seconds and then it start again. It is not the monitor loosing the sync, is the Amiga output.

I told myself that I was probably experiencing issues with overloading, but the picoATX is a 90W; the amiga1200 has just an accelerator, and the HDMI converter gets only 1A on the +5V rail, so I should have plenty of power available.

I use an ATX connector, from which I take the +12, -12, +5 and ground for the Amiga power connector; the floppy is powered from the amiga, the HDMI adapter is powered by a Y cable taking the 5V from the molex connector for the HDD (since I use the CFcard as HDD).

To verify where the problem lies, I used my 300W ATX power supply, and connected everything to it...the Amiga works fine and the screen stays up.

Tried to connect only the amiga power to the picoatx, and the HDMI adapter to the ATX power supply, and I would experience the screen issue; this demonstrated clearly that the problem is not the adapter but the Amiga output.

I have no other monitors that I can use, so basically I don't really have alternatives...

Is anyone here able to tell me what is going on? The 1200 PSU is rated at 65W if I remember correctly, and the pico is 90W (the AC used for it is a 12V 10A, so should have plenty of power); I can't believe that it is not enough to power my amiga 1200; especially because I remember of many users that were successful using it, on their expanded 1200 (I have a 040/50 with 64 Mb of ram as expansion card; not one of the most demanding accelerators I assume; while I see people using picoPSU with 060 or even PPC).

Do I have a defective PSU? Should I contact support for the PicoPSU?

[superfrog76]

It sounds like you may have a bad connection(intermittent) in the power cables, or indeed the 5v rail on the pico psu is not strong enough.  i assume the outside source has the recommended voltage-Does it need to be higher than 12v? to feed it?
Don't go by overall wattage, that assumes all power combined with a certain efficiency(usually something like 70-80%) and doesn't really mean a whole lot.
the amperage output on +5v will be more meaningful.

Thanks for the reply:

Checked the cable...so far no short circuit; tried with the impedance of the cable, and it won't fluctuate, as sign that the copper inside the cable does not have interruptions.

The outside power source is rated 10A (9.79 effective); the pico should use it at 75% probably, so let's say that it should not have problems with anything below 60W. The Amiga with accelerator should use about 15-20W.
Altho I have no way to check for efficiency and quality of the external brick...so can't exclude that it is the problem (I need a different brick and see what happens)

The pico has 2 models, which uses 19V (red connector) and 12V; I have the 12V version (yellow connector); so I think that I am using the correct voltage.

The 5V output ( the ATX connector has 4-5 5V rail, plus the one used to power the peripherals) seems to be around 4.84A, recorded at the ATX connector. Someone said to put together all the 5V rails, except the 5VSB, which output max 1A and must not be used...It may make sense to connect them all to use more power, but the Amiga requires very little current, right?
I don't have the exact requirements for the 5V rail on the amiga; I need to check the original PSU, but is hard to believe that it needs more than 5A.

Strange thou that nobody that uses it has mentioned to put together all the 5V rails...but I suspect that the issue is like you mentioned, an incorrect current on the 5V rail >_<

[superfrog76]

You lost me on the "best making 12V from higher voltage" From the little that I know; 110V to 19V is not different from 110V to 12V; feel free to elaborate because I am not an expert. Also I have no clue of what buck/boost style means

BTW the 4.84 is the current (Ampere), not the voltage; the voltage of the 5V rail is stable between 4.99-5.01V all the time. I was replying to your question, about how much current is going on the 5V rail of the PSU.

This is the page with the specs of the pico that I have:
http://www.mini-box.com/s.nl/it.A/id.417/.f

One of the link has the manual, with the various tables and technical stuff...of which I understand very little

Ok, so the pico has the same 5V current of the original, which means that it should be enough to power the mobo plus accelerator (30W peak should be plenty). On modern mobo, seems that the +5V is not that overloaded....most of the power goes on the 3.3V and 12V, so I guess that's where most of the power of the picopsu is routed (which is a shame)

I will follow your suggestion and grab another 12V brick, if that won't fix; the next step is to call the guys at mini-box and see what they can suggest.

Thanks!

[superfrog76]

NP Mechy; I thought that there was a meaning that I was not able to grasp  

So "maxed out" means I am giving too much power to the board, or the PSU is getting too little load and won't work properly?

Tried to run the converter with a different psu, and only the Amiga powered with the PicoPSU and I would still see the issue. The adapter came with a 5V power supply (like the charger for the phone, same size); tried with that, just to exclude that it was the converter.

Should I put a resistor on the 3.3V rail, for the sake of having a small load on it?

BTW just to be clear, the power is never getting shut down; the led on the pico stays solid all the time, and the amiga does not reboot; it is just the video that goes on and off.
I thought that I was getting some sort of problems related to the cut off power mechanism on the PSU, but in that case I should see the power going off; or the led flicker.

I have a fan inside the case, which blows on the pico and the accelerator; it is a Cpu fan, so not that big, but should be enough to generate some airflow in the case, so I can use the pico at full throttle if needed (altho as you noticed, I suck at most 2A/30W from the PSU, so we never even get close to the 8A top that would output at 100% load)

Well, my approach when I purchased it was dual: first, others used it successfully; so that was a big plus...and second, the original PSU is 60W, so I thought that buying a 120W PSU would be plenty (average PSU load max 80%= 96W, which is 36W more than the original PSU). At this point I wonder how others did make it work...I am reading all the posts on the various boards related to the pico, without finding a reason why mine wouldn't deliver

Thanks for helping me; you gave me new ideas to look into.

[superfrog76]

This is probably a dumb question, and not a help with your PSU issue, but why do you say the Indivision wouldn't work with NDOS games? It takes the video signal right off the chipset and scan doubles everything, I've never heard of a game or program that it wouldn't be able to convert to 31KHz.  I own two of them and have zero issues with any software not displaying correctly on modern LCD screens.  :confused:

Well, I was told that indivision works only with workbench...many were complaining about software that does not use standard resolution, which cause issues to the card. And ndos software was the main issue there.

If you tested all the games and software and never had an issue with the card; I guess that I had the wrong info. Thanks for pointing it out

[superfrog76]

Thanks Mike for the explanation...in this case I may consider the purchase then, next year thou....spent already my allowance for the Amiga, on my desktop case project LOL

Broken: Thanks for your feedback; the fact that you are using a weaker picoPSU and have no problem may be a sign of a defective PSU on my side.

Could you tell me how did you connected it? And what kind of brick do you have? Also is your PicoPSU purchased trough the original maker site or did you got it via 3rd party? (I have purchased it via Amazon; I may have a crappy clone since it doesn't say "picopsu" and "patent pending" like the pictures on the PicoPSU site)

Thanks!

[superfrog76]

I bought mine from an authorized reseller.

If yours doesn't have the patent pending markings on it, then it's a bootleg.




Sadly there are many bootleg versions of the Pico out there.

I see, so they make clones after all. Mine does not have the patent marks, but it is exactly the same other than that (has some numbers on it).

Guess the problem may be a faulty one then. Could you tell me the authorized reseller that you used? I paid mine 35 bucks from Amazon.

Also, how did you connect the amiga to it?

[superfrog76]

Soi, Seems that the picopsu is not stable enough for a digital signal.

The minimal variation in current, generates a response in the circuitry on the video port; which usually are not even noticed, since many of you uses Indivision (which bypass the circuitry at the video port, taking the signal directly from the AGA chip), or use CRT monitor, which are more lenient on current variation.

The HDMI adapter per se is working fine, except that it is made probably to work with stable signals coming from newer devices, so when the signal change, the device perceive it as if the Pal/NTSC state change,and goes for a refresh. Verified that using a CRT monitor and using the same picopsu on a different miggy, which has an indivision.
Neither show the issue, while they did exactly the same as mine, when using the pico and the Scart-HDMI combo for the output.

So, if you are in the minority that uses a SCART to HDMI solution, keep in mind that the picopsu may give you troubles....wish I knew before spending 120 for the Scart cable, HDMI adaptor and PicoPSU