0.5mb trapdoor expansion on 1mb A500+..still only 1mb ??

I have a A500+ with 1mb chipram internal.It should have been a A500 that is modified to A500+,so it´s not a native factory build A500+.
It´s a Rev 8a board and it´s Kickstart 2.0

I have a 0.5mb trapdoor expansion that I have tried to use also (it's working 100% on a regular stock 0.5mb A500 with Kickstart1.3) but the Amiga still only shows 1mb.
I´ve posted about this issue on Facebook and a user suggested to solder a 74F139 IC onto location U32 and also remove solder from the jumper pads on U32. I´ve done this(and also added a socket for the 74F139) and still there is only 1mb shown. I have tried booting without the 74F139 but it just shows a green screen. With 74F139 added it boots normally but only shows 1mb,so the 74F139 is diong something to the system.



So have anyone any ideas etc. why the A500+ don¨t show a total of 1.5mb ??
I have checked the traces using Amiga PCB Explorer site and as I can see/understand ,there is no broken traces (I´m not a electronics expert).
I´ve tested continuity with a multmeter that BEEPS when probes are connected.


Is there still some things/mods missing to the Amiga?
Could there be mods to the trapdoor in order to work with a A500+ ??

[1NOM155]

hello have you follow kipper2k guide? http://eab.abime.net/showthread.php?t=77705

Originally Posted by 1NOM155

hello have you follow kipper2k guide? http://eab.abime.net/showthread.php?t=77705

Thanks but the guide shows modifying A500 512kb rev8 board into a a500+ with 1mb...I have that already.
Need to know why the 512kb trapdoor expansion is not added to the existing 1mb so it should have a total of 1.5mb.

[1NOM155]

migth be silly but what Agnus do you have (8375 or lower)?
is possible to see details pictures of thw motherboard?

[esel]

most old 0,5 ram extensions have a on/off switch, to use it the expansion in the a500+ the expansion must be switched OFF.
in a normal a500 is must be ON to use

Originally Posted by 1nom155

migth be silly but what agnus do you have (8375 or lower)?
Is possible to see details pictures of thw motherboard?

8375

What picture do you need ? Specific areas ?

Originally Posted by esel

most old 0,5 ram extensions have a on/off switch, to use it the expansion in the a500+ the expansion must be switched OFF.
in a normal a500 is must be ON to use

The switch is removed (always ON since it works in my regular A500) but I shortcurcuit the points but no result

[1NOM155]

I dont own a 500+ but a friend of mine have one with commodore 500 ram upgrade and gets 1.5mb of chip ram. i dont know if 3d party ram expansions did something diferent from commodore ram expansion design.

Also if you have Agnus 8375 and did the same modifications like Kipper2k did, probably the ram expansion you got have some issues. I dont know what you can do more exept trying a diferent ram exp to check

probably is better to provide more information with pictures of your A500 detaling the modifications you made and also the expasion card you have, others with more experience than me might help you.

Well...It´s working now 100% ! <img src="images/smilies/biggrin.gif" border="0" alt="" title="Big Grin" smilieid="4" class="inlineimg" /><br />
<br />
Thanks to the Kipper2K tutorial even though I did refuse it first time. I did take a closer look at the modifications on finished board and compaired with mine and noticed that the JP3 solderblobs was different on mine and changed them to the way Kipper2K showed and wam bam there was 1.5mb ram.<br />
<br />
Thanks to all who took the time to post..most grateful <img src="images/smilies/smile.gif" border="0" alt="" title="Smile" smilieid="1" class="inlineimg" />

[1NOM155]

Originally Posted by cinnober

Well...It´s working now 100% ! <img src="images/smilies/biggrin.gif" border="0" alt="" title="Big Grin" smilieid="4" class="inlineimg" /><br />

<br />

Thanks to the Kipper2K tutorial even though I did refuse it first time. I did take a closer look at the modifications on finished board and compaired with mine and noticed that the JP3 solderblobs was different on mine and changed them to the way Kipper2K showed and wam bam there was 1.5mb ram.<br />

<br />

Thanks to all who took the time to post..most grateful <img src="images/smilies/smile.gif" border="0" alt="" title="Smile" smilieid="1" class="inlineimg" />

Nice mate well done