Fox-1 / mnx

DarkLord, on Sat May 26, 2012 2:50 PM, said:

Convenience is indeed one reason.

The Atari and Pico PS' are both "switching" types, but different. They don't switch at the same frequency so there is a (small) chance one will interfere the other which may result in drifting voltages.

More important, a PS creates a ground relative to it's output voltage (or the other way around, doesn't matter), like, the +5V output is 5V above ground, where ground is 0V for that PS, but it's relative. It may just be the ground is in fact +2V while the +5 output is +7V. This will still give a +5V output when compared to that ground.

When using 2 PS' (in a single unit designed for single PS usage) you always have to connect both grounds together, so if 1 PS has ground at +2V and the other has ground at 0V there is a 2V difference. No problem for a running system as both grounds will be forced to the same level (they're are connected together) but this is only true when running. While powering on both PS' there is a small delay until the voltage output is stable but it's almost certain this delay is not the same on both PS' so during that time there is a chance your output voltages are too high. It depends on the duration of the delay and the amount of difference if it can do any harm or not.

In many cases it'll just do without any harm but it's up to you to decide if "many" is enough.


Not connecting both grounds is no option as it can be pretty devastating. This is (was) one of my 130XE's:



The result of relying on main power outlet earthing as the ground connection only to discover there was none at all on the meeting we attended...

DarkLord, on Sat May 26, 2012 2:50 PM, said:

-Do you know what pin expects what voltage?
-Are all those voltages present when using a Pico PS?
-Do you have a header to connect to the STacy pins?
-Are the pins standard spacing?

If so, put a header on a small piece of vero board, make the connections on the board, plug it in.

I can do a Dutch one, albeit that many/most Dutch choose English anyways I guess :-)

If you happen to have a lot of regular serial modem cables laying around you can also make an adapter cable which turn it into a null modem cable.

DarkLord, on Sat May 26, 2012 12:06 AM, said:

However not impossible, it's advised to use a single power supply to power all components that reside in a single unit.

update:

I installed another EPROM (with v2.16 firmware) and the menu's look fine and are actually usable now. Have to be careful saying that as it's only running for a few minutes now and I don't know what will happen if the temperatures are rising.

Now I need to search for a hard disk. Yours is an unmodified black box so it only works with HD's that don't require termination power and parity.


update 2:

Don't seem to have any HD anymore that runs without parity (and termination power) so I took the parity chip from my own black box to test. Works perfectly, as expected.

Vidar:
Do you have plans to use SCSI HD's with the Black Box? If so, many recent (or better, less older) HD's and SCSI card readers require a parity mod. This is an IC that has to be installed/connected to the SCSI bus. The nice way is to replace the IC socket from the 74LS240 on the BB with one that can accept a standard header and put in a small PCB which has both the original IC and the parity IC on it. Disadvantage is that mounting a Floppy Board is not possible anymore without modifying (extending) the pins that are connected to the Black Box.

Another way is to directly mount the parity IC on the 74LS640 without having to exchange the socket on the Black Box. This solution is much simpler but looks not as nice.

If you want/need this mod I need to order a 74LS280 (the parity IC). The part itself isn't that expensive (about 3 euro I guess) but no idea yet what shipping/handling will be.

If you're not going to use such SCSI HD's or memory card readers, and if you're sure the one you have right now doesn't require the parity bit, you don't need this modification.


b.t.w: you may also answering by PM if you prefer not to write the details on the forum itself.