My HD needs ground ...

[ptek]

Hello

When I got a 3.5" HD for my A1200 years ago, I took both to a guy at an local Amiga store for him to install it with a 3.5" to 2.5" cable adapter (done by him). Everything worked fine. I got a flatcable extension short enough just to move the damn noisy HD into a box and put the Amiga on top of it.

The HD worked fine for several years. More recently, it stopped booting and it acts like it isn't powered (no spinning, no noise, nothing).

Then I open the Amiga and found this curious fact : the HD power plug doesn't have any ground cable connected! I wonder how did it ever worked. I check from this link http://www.hardwarebook.info/3.5%22_Power that only the pin 1 and 4 are wired. The voltage between them is about 8.6V (close to the theoretic expected 7V)

Anyway, the HD is fine - I plugged it on a PC and it of course sounded alive and I also managed to boot it from WinUAE.

I just need some advice from where to get a ground signal safely (I know the parallel port have ground and some other devices but I wouldn't like to blow up my fully working Amiga)

If you want to look at the place were the 5V and 12V are obtained look at the picture ... the red and black wires that go out of the Amiga go into the HD plug.
http://img164.imageshack.us/img164/9594/amigahd2mn0.jpg

[narmi]

You can use the ground connection at the floppy drive power connector.  The two middle pins are ground.  The outer pins are +5V and +12V.

I have NEVER seen a drive powered this way (without ground).  How bizarre.

[orange]

btw, don't try to use that 7VDC for whatever purpose, because the current will flow *into* +5VDC!

[Amiga4k]

Pin 1 is +5, Pin 4 is +12, with 2/3 as ground. Most PS have separate grounds. Reading across two + leads was interesting, but not beneficial.
As the IDC50 SCSI connector has 7 electrical grounds (aside from 18 electronic grounds), your "guy" might have used the ground within the ribbon cable as electrical ground. (The standard 2.5 drives use power thru the cable, right?).

Adding a ground will not hurt, but I surmise your real problem  is in the cabling. Attaching an extension, while reducing from 3.5" to 2.5" cabling has got to produce stress. Especially after years of wear, jiggling about, vacuuming, etc.

[ptek]

Adding a ground will not hurt, but I surmise your real problem is in the cabling. Attaching an extension, while reducing from 3.5" to 2.5" cabling has got to produce stress. Especially after years of wear, jiggling about, vacuuming, etc.

I think it must be a power issue (maybe ground) since if I turn on the Amiga with the faltcable disconnected the HD still doesn't spin. I think it should spin even there is no flatcable connected. At least, it happens when I power it on a PC without the data flatcable. I also remember I already tried to power the HD from a PC PSU while keeping the data flatcable attached on the Amiga - not a healthy maybe solution but it booted.

I'll try getting the ground as suggested and post the results later.

thanks all

[Zac67]

It seems to have used the flat ribbon's ground pins for ground return... :crazy: Electricity finds its own way. Those ground pins are signal ground and not power ground.

This is not at all recommended: the flat ribbon and the IDE plugs are in no way supposed to cope with the current flowing through them that way - some drives need >>1 A on startup (esp 7200 RPM ones).

Use a seriously dimensioned cable to add a ground line and if possible get a new IDE cable, yours might have been damaged by that abuse.

[Framiga]

"I think it must be a power issue (maybe ground) since if I turn on the Amiga with the faltcable disconnected the HD still doesn't spin"

thats quite obvious! Add the GND as soon as possible :-)
 


 

[ptek]

You can use the ground connection at the floppy drive power connector. The two middle pins are ground. The outer pins are +5V and +12V.

I'm going to try that. Must I connect the 2 ground connectors to the respective ground connectors on the HD plug or one one is needed ?

Another question : I will have to cram 2 wires into a single connector (like he did). Will I need any special tool ? I never used a connector like this. Is there any other accessible ground source ?

[SteveSMS]

The best would be to get a molex connector from an old PSU, and solder it. Make sure you get some heat-shrink tubing, and shrink it around the connections, that way you're sure it won't touch any other vital parts of the mainboard. Duct tape will work too, but it looks kind of unproffessional

You will need a HD molex. You can get the connector to the mainboard and the floppy from the original cable. If you want i'll post some pics how i did it.

[ptek]

SteveSMS wrote:

The best would be to get a molex connector from an old PSU, and solder it.

I already have it. Solder it to the floppy connector?!

Make sure you get some heat-shrink tubing

Why the need for heatshink?

If you want i'll post some pics how i did it.

Yes please do
Thanks

[Amiga4k]

Zac67,
If you do some research:
(1) 2.5" drives are 5 volt, and power is supplied thru the ribbon cable. Both + and -.
(2) you'll find that the commercial adapter for 2.5" to 3.5" consist of either an adapter module, or a modified flat cable. All have in common a 2 lead power plug. (No ground).

ptek,
Like I said, it's the flat cable.Somewhere in the cable it's developed a problem, and failed. Add a ground lead, and by-pass the problem.

Personally, I'd relieve the problem by adding a separate power supply for the HD. The A1200 23 watt PS was never meant to support add-ons beyond a limited range.

[narmi]

Amiga4k wrote:
Zac67,
If you do some research:
(1) 2.5" drives are 5 volt, and power is supplied thru the ribbon cable. Both + and -.
(2) you'll find that the commercial adapter for 2.5" to 3.5" consist of either an adapter module, or a modified flat cable. All have in common a 2 lead power plug. (No ground).

2.5" drives are powered through four extra wires in the ribbon cable: two +5V and two ground.  Two wires are used for each supply line to allow sufficient current to flow.

Every 2.5" to 3.5" adapter I have seen include a two lead power connector, with one wire for +5 V and one wire for ground.  This connector is used to power a 2.5" drive, there is not enough power available at a 2.5" drive connector to power a 3.5" drive.

Good practice is to include one ground wire for each power wire, with both wires being the same gauge.  This allows all current flowing in through the positive lead to be returned to the power supply (thus following Kirchhoff's current law).

[ptek]

I'm just surprised how stupid I was! The data cable was inverted! Not healthy since pin 1 have some voltage, I think.

So everything works again. And "look ma, go ground"

Anyway I guess i'll dig at the forums for a flash disk replacement. 1 Gig will be the double I have on the HD and will fit inside the Amiga and it's quiet. Any suggestions?
I wonder if i'll notice any speed difference in reading operations. I don't pretend to write often at these times.

I use the A1200 normal non-buffered IDE port for the HD.

Thanks

[Homer]

Hmm, yes, you forgot to mention that you had broken it yourself  :lol:
If the replacement drive takes more current than the present one (It will be written on the label on the drive), then I would advise you to do the molex modification mentioned earlier.
Oh, and have a :pint:

[ptek]

Hmm, yes, you forgot to mention that you had broken it yourself

well, that was implicit It must have happened when I tried to plug the HD to the PC for trying UAE and plugged it wrongly at the Amiga. But it works, nothing was damaged (as it looks).

If the replacement drive takes more current than the present one (It will be written on the label on the drive), then I would advise you to do the molex modification mentioned earlier.

I'll go for a flash drive. I guess (hope) it uses less current. Anyway I'm using an old brick PSU of 60W from a Amiga 500 since my A1200 PSU died - I bet it was the HD demands that knocked it off...