A500 trapdoor memory: free design

[Nbdy]

Swapping the wires didn't do any change ...

THe 139 is soldered well ...

Rechecked all the RAM chips, all are OK soldered ...

Could the problem be in the caps what where missing that I added ???

C13,C14,C15,C6 ???

I also resoldered the gary chips ...

[Mathesar]

Could you try setting the 3 jumpers on the gary adapter to the 0,5mb chip setting?

[Nbdy]

All 3 jumpers UP (left side) ...

Green screen and 10 times power led blinking ... reset ... repeat all ...

[Mathesar]

Hmmm. Putting the jumpers UP simplified the RAM bank selection process. So if something in the Gary adapter was wrong this setting could have helped. I'm beginning to suspect your RAM chips are faulty.

[Nbdy]

Hmmmm, bought a kit, all was like new ....

COuld I change one by one with that hynix some posts before ???

HY5118164B - have 8 of them ...

And to ask, if it shows 1.5MB slow, so one of the chips is faulty or ???

[Mathesar]

Maybe there is a way to test your trapdoor RAM board.

- Remove the Gary adapter and set JP2 on the Amiga motherboard in the original position.
- If I understood correctly you saw 512kb chip + 512kb slow in this setup.
- Now, run Amiga test kit or so to test the slow ram
- Next, you can select each of the 4 RAM chips by putting logic levels on the 2 link wires going from the Gary adapter to the trapdoor board. If both link wires are jumpered to ground, bank#0 is selected, both to +5V selects bank #3, one to ground and one to +5V selects bank #1 and #2 (depending on which wire goes to ground and which to +5V).
- test again.

This way you should be able to test all RAM chips on the board.

[Nbdy]

Originally Posted by Mathesar

Maybe there is a way to test your trapdoor RAM board.

- Remove the Gary adapter and set JP2 on the Amiga motherboard in the original position.
- If I understood correctly you saw 512kb chip + 512kb slow in this setup.
- Now, run Amiga test kit or so to test the slow ram
- Next, you can select each of the 4 RAM chips by putting logic levels on the 2 link wires going from the Gary adapter to the trapdoor board. If both link wires are jumpered to ground, bank#0 is selected, both to +5V selects bank #3, one to ground and one to +5V selects bank #1 and #2 (depending on which wire goes to ground and which to +5V).
- test again.

This way you should be able to test all RAM chips on the board.

Will try, well with the JP2 in original position i had 512 chip + 1.5mb slow ...

Going to retest all that ...

THX

writte the results ...

OK, now seeing 0.5+0.5 ... without the gary adapter, with the gary adapter I had 0.5+1.5 ...

EDIT : Hmmmm ....

Have all 4 banks ...

1. Both wires to GND ... 0.5+0.5
2. First to GND Second to 5V .... 0.5+0.5
3. Second to GND First to 5v .... 0.5+0.5
4. Both to 5V .... 0.5+0.5

Tests taken to 15-20 passes, all OK ...

I'm suspicious of the gary adapter ...

Like the pin 14 was not connected as it should ...

Is there any new shematics to test the board ???

Ordered 5 PCS from ELECROW, now waiting to arrive ...

Maybe the gary board is not OK at all ...

[Mathesar]

There is no easy way to test the gary adapter. But good to hear the tests of the trapdoor board worked. I guess that one is OK indeed.
The gary adapter does mainly 3 things:
1) Mess with RAMEN into gary so that the whole addres space $C00000 to $D7FFFF makes the trapdoor RAM visible so to say. Apparently, that is working as you can see 1,5mb of slow with the gary adapter in.
2) Next, the gary adapter must make sure that each RAM chip responds to the correct address. This is what the 2 wires to to the trapdoor do.
3) The adapter must also tell Agnus whether the CPU is acessing chip or slow ram. This is what the wire to JP2 does by controlling A19 into Agnus.

Step 3 is the most suspicious step I think.

[Nbdy]

How to check it ???

[Mathesar]

Originally Posted by Nbdy

How to check it ???

Not straightforward unfortunately.
Note that it could still be the '139 chip on the trapdoor board that always selects the same bank. However, that is unlikely imho.
All I can recommend is to check all solder joints on the gary adapter or, as you are already doing, build a new one.

[Nbdy]

The PCB-s came yesterday, now the chips should get today, will build another one and test ...

Writte the review ...

Another question, could I use the Hyundai rams HY5118164B for the expansion ???

[Nbdy]

https://www.aliexpress.com/item/1005...d=bF4ODeMqVR9d

Will this be OK for the MBO connector ...

I have googled for 2 hours not finding a similar connector ...

THX

Or a link could be werry useful ... :-)

[Mathesar]

Originally Posted by Nbdy

https://www.aliexpress.com/item/1005...d=bF4ODeMqVR9d

Will this be OK for the MBO connector ...

I have googled for 2 hours not finding a similar connector ...

THX

Or a link could be werry useful ... :-)

What do you mean with MBO connector? The link shows some kind of card edge connector. Do you mean the pins for connecting into the motherboard socket? Like these: https://nl.aliexpress.com/item/40011...d=IXJFqih6H4yY

( select 2.54 1row male gold)

[Nbdy]

Originally Posted by Mathesar

What do you mean with MBO connector? The link shows some kind of card edge connector. Do you mean the pins for connecting into the motherboard socket? Like these: https://nl.aliexpress.com/item/40011...d=IXJFqih6H4yY

( select 2.54 1row male gold)

Nope, for connecting the memory board to A500 ...

O man I'm so stupid, all time thinking of card slot, not pin slot ...

I suppose I can combine 2x20 and 2x8 to get 2x28 ???

Cccccccccc


My fault .... even the components didn't still arrive, so waiting to complete the second gary adapter ...

[Nbdy]

OK, all is OK ...

Soldered a new gary adapter, and now all works well ...

Testing the memory ...

BUt now I have 1MB chip and 1.5MB slow ....

[Mathesar]

Originally Posted by Nbdy

OK, all is OK ...

Soldered a new gary adapter, and now all works well ...

Testing the memory ...

BUt now I have 1MB chip and 1.5MB slow ....

Good to hear all is working!

[Nbdy]

@Mathesar ... yep, thx for guiding to solution ...

Could you be so kind and tell me if the HY5118164B ram will be fine for the expansion to solder one more ...

And please will the 20+8 dual pin be ok

https://www.aliexpress.com/item/4000...d=6Vr1ioVm42Uw

[Mathesar]

Originally Posted by Nbdy

@Mathesar ... yep, thx for guiding to solution ...

Could you be so kind and tell me if the HY5118164B ram will be fine for the expansion to solder one more ...

And please will the 20+8 dual pin be ok

https://www.aliexpress.com/item/4000...d=6Vr1ioVm42Uw

I also used a combination of smaller dual pin headers. Sometimes you need the grind the edges a bit to make them fit together snugly. Ram looks OK to me.

[Nbdy]

Originally Posted by Mathesar

I also used a combination of smaller dual pin headers. Sometimes you need the grind the edges a bit to make them fit together snugly. Ram looks OK to me.

THX


Now going into soldering for 2 more pcs ....

[Nbdy]

Hmmmm ....

Looking now at the PCB that arrived i think it's the rev.6 ...

There is no connection on the ram chip on the bottom side to RASU4 ... (the only chip side) ...

Should it not be bricked to RAS1 ??? for all the memory to be active ???

On my red board (this one are green) the RASU4 is shorted to RAS1 (page 30 pictures) ...

And have seen that a lot of CAPs are missing, they are not needed any more or ???