ACA500plus black screen

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Don't Panic. Please wash hands.

    Hi there,


    I am having trouble getting my Amiga 500 to boot after installing the ACA500plus.


    Note: I also have an Indivision installed for VGA output and I believe this is a v1 Amiga 500. I removed the memory expansion and cleaned the board edge connector.


    The display on the card along with a blue LED turn on, the 7-segment DisMo display then cycles through a few numbers while the VGA display is green then stops at 20 for a while. After that the blue LED goes white, DisMo reads 8.8 and the screen goes black. The power LED does not light up.


    When I unplug the ACA500Plus the computer boots fine to the workbench disk screen and the red power LED lights up.


    Please help! =O Thank you very much.

    That connector does look a bit bent, but I'd expect that the contacts will be pushed up by the Amiga side and work fine. Please follow the procedures mentioned in the short manual: Clean the Amiga side with alcohol and a micro fibre cloth, this will solve possible contact problems. If the DisMo shows a few changing numbers (or even just the cycling animation at power-up), there's already a lot that works, as that is all launched by the processor of the ACA500plus. Also, the unit has passed our QC procedure, where all flash contents are programmed into the local flash from CF card, and a total of three reboots and two power cycles happen. If the card had any trouble during that procedure, it would have been put into the "repair me" box.

    As I said in the first message, I already cleaned the contacts. Twice in fact. Once with an eraser as the manual says explicitly to do, and another time with 99% isopropyl alcohol. This didn't change anything.


    Edit:


    In case this helps in troubleshooting, the board cycles through the following numbers:

    - LED is blue, startup animation

    - 00

    - 05

    - 06

    - 20 (hangs for 20 seconds),

    - LED turns white and display changes to 8.8 screen goes black (tried two different screens)


    Lastly, just in case this question comes up. I bought and am using the following Amiga power supply from C64PSU.


    Thanks

    OK, we've had that PSU as a source of problems before. Quit using it. It is largely unregulated and even dangerous to the computer. Use any old 2.5A power supply, and your computer will work fine.

    Errm, NO. ATX power supplies mostly have the 12V rail as their main regulation rail, but that's pretty much unloaded if used on an Amiga. As a result, the 5V rail will become "mostly unregulated", which may even destroy the Amiga. If you can, please use an old original PSU - if you do want to modify something, exchange the secondary electrolytic caps, but please avoid messing with an ATX PSU unless you know for sure that each voltage rail has a separate DC-DC converter.

    Jens thanks. I have no option to use the original PSU as the Amiga I have is from EU and I'm in NA. I don't have a 110>220 transformer.


    I will search for a power source that is properly regulated. Can you be more specific about modifying the secondary electrolytic caps? Is there an article somewhere I could read up on?


    Edit


    What are your thoughts on the Meanwell RT-65B (datasheet here). It seems to have the necessary outputs along with more than enough current, and is affordable.

    The RT-65B Chassis is about the only descent PSU I'Ve seen lately, but on the downside, the ripple specification has been increased about a year ago (so higher ripple on the same chassis number). The PDF in your link shows 80mV p-p for ripple, which should be fine (although larger than 1%). It used to be 50mV, so if you can get the older version, that would be even better.


    Please note that I can only endorse using this chassis for people who have the proper education working on mains voltage. Serious injury or death may occur if you make a mistake. If you don't feel fit for such a modification, please get help from a properly educated person.

    Quote from Jens

    The RT-65B Chassis is about the only descent PSU I'Ve seen lately, but on the downside, the ripple specification has been increased about a year ago (so higher ripple on the same chassis number). The PDF in your link shows 80mV p-p for ripple, which should be fine (although larger than 1%). It used to be 50mV, so if you can get the older version, that would be even better.


    Please note that I can only endorse using this chassis for people who have the proper education working on mains voltage. Serious injury or death may occur if you make a mistake. If you don't feel fit for such a modification, please get help from a properly educated person.

    Thanks again Jens. I've been working with electronics and AC electricity for years, I'll be around to bug you if the upgraded power supply doesn't work ;)


    I'm surprised that the Amiga power supply that I purchased isn't suitable, could you put a warning on the Wiki page regarding using an appropriate power supply? It could help others in my situation avoid some hassle and headache.

    Quote from blark

    I'm surprised that the Amiga power supply that I purchased isn't suitable, could you put a warning on the Wiki page regarding using an appropriate power supply? It could help others in my situation avoid some hassle and headache.

    That would be the destructive way - I think I've already gone a more community-like route by contacting the vendor and making him aware that he's putting classic computers at risk.

    Quote from Jens

    That would be the destructive way - I think I've already gone a more community-like route by contacting the vendor and making him aware that he's putting classic computers at risk.

    Well considering they are still selling those power supplies (as I just bought mine) it seems like they are ignoring you. Hopefully anyone looking for power supply advice will happen across this thread...


    Also, consider just listing "approved" supplies. I wasn't suggesting a blacklist.

    So we're talking about a similar model to the RT-65B chassis, with the same lowered ripple rating. The chassis does seem to allow adjusting the voltages, so what you could do first is to adjust +5V and +12V to meet requirements if measured at the input of the Amiga, and to add a huge electrolytic cap on the 5V rail to reduce ripple.

    I don't see any pots on the RPT-60B board for adjustment, I've ordered a RT-65B it should be here tomorrow.


    Just so we're clear, how many micro farads is "huge?"


    I have an oscilloscope too, so if necessary I can get accurate readings to completely rule out the power supply as the issue... more to come tomorrow. Thank you again for the help.

    Quote from blark

    Just so we're clear, how many micro farads is "huge?"

    30 years ago, I would have answered "at least 1000µF", but these days with low-ESR caps available, I'd start with 470µF and choose a voltage at least three times as high as the voltage on the rail. That would be a 16V type for the 5V rail, and a 50V type for the 12V rail. The 12V rail may be as important as the 5V rail, alsough it does not contribute directly to stability of the A500. However, the construction of the PSU hints at both voltages being generated from the same high-frequency transformer, so both are regulated with the same regulation loop. I'd therefore expect to see cross-regulation problems especially if the 12V rail is not loaded.


    Low-ESR and high temperature rating make these caps very expensive, which I speculate to be the cause of the reduced ripple rating of the MeanWell chassis.

    Jens the power supply shipment was delayed until today. I do happen to have some 1000uF 50v caps here that I will try on the 5v line. I'll also measure the voltage to make sure that it is stable at 5v. I anticipate trying all this today, I'll report back soon.

    I've retrofitted 3 Meanwell RT-50B power supplies in 3 heavyweight A500 power bricks, that I am using with :

    1. Amiga 600 with Furia 020 accelerator, Indivision ECS, and IDE CF adapter

    2. Amiga 500 with ACE-2, ACA500+, ACA1221ec @ 42MHz (with heatsink), X-Surf 500, Indivision ECS.

    3. Amiga 500+ with TerribleFire TF530 @ 40 MHz

    4. Amiga 1200 with ACA1233n accelerated to highest warrantied speed.

    5. Amiga 500 with ACA500+ @ 21MHz and sometimes 28MHz.


    In all cases, those power supplies have performed absolutely brilliantly so far without an issue. The only issue I've ever had was a system hang once on the Amiga500+ with TF530, but that could have been due to something else completely unrelated to power.


    KKR75

    KKR75 thanks for the feedback, looks like the RT-50B and 65B are very similar. The 65B just has a slightly higher rated current output... Shipment was delayed again, should be coming in today so I will have a chance to hook it up and test it out.

    Jens so I finally have a resolution to my issue, as it turns out it was the bent pins (pictured in my second post) causing the problem. I assume they were not making contact with the Amiga.


    I wired up the new RT-65B power supply (tuned the 5v line under load) and again had the same "black screen" issue as before. Disappointed with the result I decided to try to bend the pins back into shape. I used a pair of very fine tweezers that I use for SMD soldering to bend them as close as possible to the other pins. I used a pair of 3.5x magnifying glasses to make sure that I wasn't shorting anything out.


    Sure enough after re-seating, the card worked immediately. I'm very glad to finally have the issue resolved, and have my aca500plus working!

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