SubSystem A500 from Pacific Peripherals

Rakeim132

Well-known member
Joined
Jun 12, 2010
Posts
1,999
Country
Australia
Region
Gold Coast
Hi everyone,

I just got my hands on a SubSystem500 which allows the Amiga 500 to have 2x Zorro II ports (like A2000) and an external floppy drive.
It's a very exciting piece of hardware I will restore it carefully.

- The PCB is in mint condition.
- The floppy drive looks really great but will be replaced by a beige one.
- The case needed a good clean and all the screws need replacement, which they will receive.

It's now time to put it back together, but I have one little issue: I do not have the power original power supply and I don't know the specifications of it. Would someone have one and is able to confirm it's only +5V as it seems to be when I look at the circuits? Thanks a lot. I'm interested in knowing the Amps as well.

My intention is to install a small internal PSU inside the 1U rack and to power it directly from the back. I'll replace the DIN connector and the switch for something 240V / 10Amps rated. The internal PSU will have capacity to power +5V and +12V but I will only use the +5V for the Zorro II boards as I believe the +12V comes directly from the floppy cable.

Any hint for the power supply would be appreciated. If you have one of these, please post photos. I will add more pictures if this thread gets some interest.

The SubSystem500 will be connected to an A500+ with internal accelerator and all bells and whistles for classic (not Vampire). Interesting bit is there is a pass-through for the A500 Zorro Port so I should be able to use a GVP HD8. As for the Zorro card I'll be looking at a Picasso II (or GBA PII) and a XSurf3 or Ariadne II network card, which I need to buy, so I'm taking offers too, lol.

Pacific_Peripherals_ad.jpgSubsystem-500.jpgSubsystem 500-2.jpg
 
Last edited:
Zorro II uses all +5 +12 -5 -12 voltages, pinout here, so you can reverse-engineer which of these come from the PSU connector and which from the sidecar connector (for sure the sidecar doesn't carry -5 as it isn't provided by the A500 PSU, -12 is low amp enough so it could conceivably come from the sidecar, but +5 and +12 must come from the dedicated PSU, as must the non-provided -5V).
The floppy doesn't use +12V it's slim low-power design, +5V only, so I doubt the floppy port's +12V is even connected, but even if it is it'll be dedicated to the floppy for the obscure possibility of a 1" floppy requiring +12V for the flywheel motor (never seen one).
If I'd have to guess, extrapolating from the PSU rating, it'd be something like +5V/7A , +12V/1.5A , -12V/0.15A, -5V/0.15A, which is just slightly overshooting it, with the possibility +5V being provided at two of the six terminals of the DIN socket.
 
Last edited:
You impress me.

However the DIN connector only received 2 wires. They are using 2 pins each but I guess just for the purpose of increasing the Amps.
I have traced continuity of one wire to the +5V of the Zorro II pads (5th pad from end). The other wire is definitely ground. The ON/OFF switch cuts the +5V. Very simple wiring.

The floppy drives receives a fully wired Molex connector with 4 wires. Connection is from the PCB. The DB23 converts into a 26pin connector, then on the PCB is why looks like a floppy controller and the floppy is connected by a 34pin flat ribbon plugged in corresponding connector on the PCB.

I have to guess that the Amiga supplies all other power requirements +12V and others. Hopefully it’s enough juice for 2 Zorro II cards?

So if the PSU only supplies +5V, I guess the +5V from the A500 connector is not connected to the PCB. I will check that.

I will put pictures of the PCB tomorrow. Might tell us a lot. Cheers.
 
I have to guess that the Amiga supplies all other power requirements +12V and others. Hopefully it’s enough juice for 2 Zorro II cards?
Quite possible, both A500 PSU types are 1A rated on +12V so if the ZII cards aren't too demanding on +12V, it'd be OK. The SubSystem floppy definitely doesn't use +12V so whatever amperage is left could keep ZII happy.
After all, only cards like HD controllers that can take an HD would need +12V of any meaningful amperage (for the HD motor) - and the dimensions of this case rather render this impossible or impractical in the first place. Logic-only cards wouldn't need +12 at all, save perhaps high-speed I/O cards that would still require +12 and -12V for RS-232 compliance.
As for -5V I don't even know where it'd be used, it was dropped on A4000 PSUs too, so no big loss not having it either. Probably no real-world cards need it, it was likewise dropped from the ATX standard eventually.

So if the PSU only supplies +5V, I guess the +5V from the A500 connector is not connected to the PCB. I will check that.
Probably not - at least it wouldn't make much sense because it'd have to be separated from the +5V coming from the SubSystem's PSU. No reason to complicate the design with two separate power planes.
The +5V on the sidecar passthrough might still come from the A500 though, that's an easy continuity test too.
 
So, here are some pictures of the internal PCB (very simple).

First of all, the electrical circuit with only 2 wires coming from the DIN connector and going to the PCB and to the rocker switch at the front of the case:

IMG_0445.jpg

With a little zoom on the DIN connector receiving the external power supply (which I don't have). It's not obvious as I have de-soldered the black wire to remove the connector from the case but each wire is connected to 2 pins to increase the amps through the plug:

IMG_0446.jpg

Now the floppy drive controller circuit, on the PCB and the 3 connectors for the flat ribbons:
- the 26 pins receive the connection from the DB23 floppy port from the Amiga
- the 34 pin is going to the floppy drive
- the small 4 pin on the right are the power connector for the floppy drive.

We can also see where the power supply arrives on the board from the PSU:

IMG_0447.jpg

And finally the "back" of the PCB with the 2x Zorro ports for the boards and the Zorro pass-through (on the right) to connect an A590 or an HD8+ external hard drive (or an ACA500+ ?). We can see a red wire which seems to be the +12V going to the floppy power cable connector:

IMG_0448.jpg

Any suggestion ?
 
Last edited:
Well yeah, white = definitely +5V, black = definitely GND, you don't need the +12V red wire for the floppy, no real-world 1" slim floppy will use it, you can desolder it. It wasn't meant to be there in the first place. The LS74 and LS38 chips are the flip-flop and NAND gate typically found on external FDD circuitry so this probably takes "amiga" drives, not unmodded PC ones. The other hidden Motorolla chip I don't know about, what is printed on it?
What I can see is that the 26-pin connector for the floppy doesn't connect any power -neither +5V (which comes from the PSU) nor +12 (which isn't needed, and here comes from a hack).
There are two surrounding holes where the PSU wires end up on the PCB, but I guess they're shorted to their nearest hole and not meant to provide extra voltages.
At least the one next to ground is connected to the GND pins of the floppy connector.


So yeah this seems ready to go once you connect a suitable PSU. Considering a 5V only PSU, it should be around 11A (as they mention a 54 watt PSU in their product sheet).
 
Did you get any installation disks with the SubSystem? The reason why I am asking is that I have a Pacific Peripherals Overdrive Zorro SCSI host adapter and part of the disk (with the harddisk configuration program) was not readable. I know that Pacific Peripherals sometimes included the Overdrive with the SubSystem.
 
@BLTCON0
Thanks mate, for your confirmation. Yep, I will find a small 55W PSU and will stuck it in the 1U rack (if I can).
Yes the drive seems to be an Amiga one and I will replace it with an A2000 one (beige instead of black, not sure why they took black drive in first instance).
Here is a close-up of the Motorola chip:
View attachment 146426

@CStich
Nothing came with it abut a disk was left in the floppy drive which I thought was just for transport. I will check on this disk (if anything Amiga related) but I don't think any driver is needed...
Oh and yes, their advertisement says one of the nice Zorro peripheral to be mounted in the SubSystem is the Overdrive. :smile:
 
@Rakeim132
A2000 floppy drives are 1.6" instead of 1" and use +12V so they were not meant for this SubSystem - aside from the hacked +12V which might be alright, they won't probably fit physically. Better mod a standard 1" PC drive or steal one from a standard external enclosure.

@CStich
Pacific Peripherals became Interactive Video Systems and later on they made this SCSI controller so maybe you could get lucky with its software if by chance they're compatible. Yeah, shot in the dark.
Other than that here are two ROMs for the OverDrive, don't know if you could get them to initialise though. Heck I don't even know the driver name.
 

Attachments

  • overdrive.zip
    7.8 KB · Views: 0
SubSystem A500 from Pacific Peripherals

@Rakeim132
A2000 floppy drives are 1.6" instead of 1" and use +12V so they were not meant for this SubSystem - aside from the hacked +12V which might be alright, they won't probably fit physically. Better mod a standard 1" PC drive or steal one from a standard external enclosure.

Actually the black floppy drive which comes with the SubSystem is 32mm thick, which is not 1.6”, more 1.25”... that’s what I’m after now, I really thought it was A2000 ones as it is from the same period.
 
Last edited:
You're right, the A2000 ones are 1.25" tall. Must have confused the extra-tall 3.5" drives (1.25") with 5.25" drives which are indeed 1.6" tall.
So the nomenclature should go: 1" = slim, 1.25" = standard, 1.6" = tall (and the USB ones maybe ultra-slim at 0.65" )
Well then, an A2000 FB-354 or equivalent will do (and you get to keep the +12V patch wire, but if your replacement PSU provides +12V too I'd rather feed the drive directly from the PSU and not via the patch wire).
 
Last edited:
Actually I'm was thinking about using a +5V 60W PSU for LED strips, so it can supply 12 Amps on the +5V, but no 12V.

But with what you just said I have another slim PSU I will probably use (industrial type), 60W too and with +/-12V as well ; as far as I can read the specs it supplies 10 Amps max load on the +5V so it should be perfect. It's very compact so probably perfect for this application...

I think I have a plan forward now, I will keep people posted with pictures of the build.:)

Thanks for your help and interest.
 
Thanks for the replies. I did try the IVS software but it didn’t work (says no IVS card found). I didn’t yet try to hack the product id in the software (the manufacturer ID of the Overdrive is already the IVS id).

the two ROMs are probably those that I sent to Toni Willen. The Overdrive does not do SCSIDirect though it has a rudimentary understanding of Rigid Disk Blocks. Toni got an emulated Overdrive to work with an existing partition but I haven’t had much luck yet. Toni thinks it may be a reselection issue (the Overdrive has no clue about reselection). I’ll try again with my ancient Miniscribe M8425S or the equally ancient Seagate ST296N.
 
So here are the changes I decided to make to the original design:

- integration of a small industrial PSU (60W) delivering +5V to the PCB and powering the floppy drive directly (with +5V and +12V);

- PSU is internal so new wiring harness installed and DIN connector replaced by direct power cable and nice pass-through grommet. Harness is fully isolated and installed low to allow for Zorro boards clearance if/when installed;

- ON/OFF switched replaced by 250V rated one;

- internal fuse installed;

- floppy drive replaced by A2000 one (beige). Waiting for delivery from eBay on that one...

- aluminium case thoroughly cleaned (as new!) and all screws and spacers replaced by new stainless steel fasteners;

I have also designed a plastic bracket which will be hot-glued inside the case and onto which the PSU will be screwed in place. Print is at Shapeways at the moment and coming to Australia soon... I can’t completely close the case yet but hopefully next week.

Now photos...

Pic1.jpg

Pic2.jpg

I’ll publish more photos when the case will be properly closed.

Project will go with A500+ with TF534 and dual boot 1.3/3.1 (with Indivision ECS V2).

I’m looking for a PicassoII and a network card (Ariadne2 or Xsurf or other ZorroII card), and an A570 to be used on the pass-through Zorro bus on the side of the SubSystem500. If you have any of these for sale, please PM me. :)

Will be a nice little classic system once completed. Thanks for watching. :)
 
Last edited:
Back
Top Bottom