Posts by blark

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    Thanks for the clarification Jens your time is appreciated!

    I did read the wiki, several times. I even tried to search for "chipram" to make sure that I wasn't missing something. I think that the wiki would benefit from a bit of additional clarification so that folks like me are _absolutely clear_ how to set up their aca500plus in this scenario.

    Could you please clarify for me the three settings I mentioned earlier:

    • $C0/Trapdoor RAM
    • 7M Fast RAM
    • 1M Chip RAM expansion

    For a 1meg chip ram setup, what *exactly* would these be set to? I am not sure what you mean by "No need to mess with $c0 memory"... does this mean I leave it as default, turn it off, etc? So you providing the exact options for a know-good 1meg chipram config would help folks experiencing problems (like bad memory) rule out aca500plus config as the reason.

    Thanks very much!

    Jens thanks. So, to be clear, on a rev 5 motherboard all that needs to be done to get 1 meg of chipram is to:

    - replace Fat Agnus 8371 with an 8372A,

    - switch on the chipram option and turn off $C0/Trapdoor RAM in expert settings

    Can I suggest that you make a note about this in the Wiki? As far as I can see it's not documented, and it might help out anyone in my situation in the future.

    Edit: One last question, would there be any problem on the aca500plus with flashing the DiagROM so I can test the memory expansion I have?

    Thanks very much.


    I have my aca500plus connected to a rev 5 motherboard. I have an amram-x 512kb expansion, and an 8372A Fat Agnus and decided to give upgrading to 1mb chip ram a try.

    I have cut JP2 and soldered the top pads as per instructions on the net. According to what I'm reading all I should need to do now is turn the amram-x to "off" and it should be detected as chipram. However the aca500plus lists the ram as "unavailable" when I do this, when I turn it on and boot the Amiga it sees the ram as built-in (forget the exact term) and boots fine. I have _not_ cut the line near the trapdoor (EXRAM) because I from what I read the off/on switch on the Amram-x should take care of that.

    However, I am having some issues with the upgrade as it seems that SysTest (crashing) and other utilities designed to check memory are finding errors. I was hoping to confirm the proper settings for this configuration so I can 100% rule out a configuration problem and move on to hardware troubleshooting. I am wondering what the various ram options should be set to? Currently they are (with the ram switch ON - because OFF == aca500plus doesn't see ram)

    • $C0/Trapdoor RAM: disabled
    • 7M Fast RAM: max
    • 1M Chip RAM expansion: built-in

    I read somewhere that I might need to make a modification related to the ROM (apparently EPROM based ROM chips require extra wiring), but I am not 100% sure what to do about this since my ROM is technically coming from the aca500plus.

    Any help or insight you could provide would certainly be appreciated. Thank you!

    Ok, I think I figured it out, the key was in this sentence of the above doc that I posted: "Note that only the P9B pins 19-40 actually have a header soldered in in most machines"

    This seems to make sense because the header is 22 pins... Jens is this correct?

    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!

    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 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 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.

    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.

    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.

    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?


    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.

    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.


    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.


    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.