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Amstrad PCW 9512 External 3.5" Drive Problem

Started by P5ychoFox, 15:52, 21 February 18

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P5ychoFox

I have an Amstrad PCW 9512 with an external 3.5" floppy drive and am hoping to get it working but have no power supply for it. The PCW itself runs fine (after a new drive belt) but I've never, until now, bothered with the external 3.5" drive. The drive is connected inside the PCW to the spare ribbon cable for the second drive but it came with no power supply (it has a jack for one).

I've tried a suitable head at 5v and swapped the polarity but there's no signs of life from the external drive. Perhaps the voltage is wrong, I'm not activating the drive correctly from CP/M or maybe it's just broken. I hoped someone here may have some pointers as I've never used a 3.5" drive on a PCW before but would like to get it running to assist in perhaps dumping some old rare PCW games I have.

I've also made a short YouTube video that pretty much covers the above:

https://www.youtube.com/edit?o=U&video_id=rioTPmOhlxk

robcfg

Hi!


Could you try to take some close pictures of the jack zone and the disk drive's PCB?


If we can identify the model of the disk drive we may find some more info.

ComSoft6128

#2
Hi P5ychoFox,

I have a PCW 8256 upgraded to 512K in the "Amstrad cupboard from Hell" here, it is equipped with an external 3.5" drive. The last time it was used was about 20 years ago but I don't remember using an external power supply for the drive. Also, I may be wide of the mark but doesn't the 9512 already have an internal power supply for a 2nd drive?

Cheers,

Peter






P5ychoFox

#3
I've attached below links to a few pics of the power jack and drive information. There is a spare power connector inside the PCW for a second drive but I wonder why this wasn't used and the drive kept external.

<img src='https://i.imgur.com/46Tfv7Z.jpg'; />

<img src='https://i.imgur.com/95KN98b.jpg'; />

<img src='https://i.imgur.com/k8agmYW.jpg'; />

GeoffB17

I've got a 3.5" drive attached to my PCW 8256 as B:, using a 5v power supply (just a standard one bought from Maplin) and it works fine.   I use the external power supply to ease the load on the power supply within the PCW.

The drive should show some sign of life.

However, I'm just wondering - given the age you say the drive is, maybe back then some 3.5" drives needed 12v supply as well?   As another poster says, you need to note the model number.

Geoff

ComSoft6128

Geoff,

Pretty sure you are correct on this. The CPC's always required an external power supply for a 3.5" B drive but I don't think this was necessary on the PCW due to the different hardware.

Cheers,

Peter

robcfg

I have a similar external unit with the same disk drive, but mine gets its power from the floppy cable, that ends in a centronics connector.


Chinnery

#7
Looking at the photo I would suspect it needs a 12v power source. there seems to be a regulator that will probably drop the 12v down to 5v. Don't take my word for it though, but a close up of the markings on the black "chip" near the rear of the drive may help.


ok. a quick check on the photos and I am fairly sure that is a 5v regulator. The drive doesn't need the full 12v so a power adapter around 7v to 7.5 should work. Again best get a second opinion.


There is a potential of a minor hack to get it to run on a 5v supply if you bypass the regulator.

GeoffB17

I was basing my thoughts on the fact that older PCs (say 386/486 ones) always had the power cables for two floppy drives, and the power cables were always two of the larger connectors for 5.25" drives, and two for the 3.5" drives, and 4 wires to all of them, i.e. 12v and 5v.   I'd assume that the later drives, that needed the 5v ONLY, just did not have the 12v pins connected to anything.

Geoff

robcfg

I think that @Chinnery is right.


For the regulator to supply 5v, you must feed it 7-7.5v. Otherwise, the regulator will send no voltage at all to the drive which explains the behaviour you describe,


Now, the only problem is to make sure you use the right connector polarity. On a good case you'll blow up the regulator and on a bad case you may damage the drive.


Would you be able to test that?

P5ychoFox

I have a multi head PSU that can do 7.5v and I can swap the polarity. Don't know if there's any way of discerning the correct polarity other than trial and error. I have a multimeter so can check if 5v reaches the drive.

Chinnery

Can your psu output more than 500ma? it should give a rating of its output somewhere.
Probably the safest thing to do is unplug the power connector from the drive and use your multimeter to test the connector itself, keeping the drive isolated. What you are looking for is when you put your red multimeter on the red side of the power connector, and black to black, the voltage should be 5v or slightly more.

P5ychoFox

My PSU outputs 500ma. Just tested the power jack & voltage regulator using my multimeter (with the connector unplugged from the drive) and at 7.5v around 11v is reaching the voltage regulator (high as it's not under load?) but no voltage is getting past the regulator so it looks like that is faulty. Perhaps it may be best to rig the drive up to the internal power?

Bryce

Chinnery is indeed correct, but you'll need more than 7.5V. Anything between 9 and 12V will work. The 7805 has a dropout voltage of around 3V, so you'll need at least 8 (5+3) as an absolute minimum before the 7805 outputs anything. The positive should be in the centre, negative on the outer ring. 500mA is cutting it close though. The regulator is a 1A part, so the drive may have peaks above 500mA that the supply would have problems covering.

Bryce.

P5ychoFox

#14
Just hooked up a 10v 1.2A power supply and measure about 13v going through the power jack but zero volts are getting past the voltage regulator to the red and black wires on the white plastic connector that would normally be hooked up to the drive. Then I tried with a 12v 2A power supply and again got no output from the regulator.

GeoffB17

I didn't catch if you'd determined if the drive needed 12v directly, or it uses the 12v merely to step down via the regulator etc to give 5v.

Either way, I'd suggest you try to connect the 5v to the drive directly.   It may be worthwhile to confirm that everything does work, i.e. the data connection, and the actual drive.   Once you're sure everything is OK, then sort out running the drive via 12v, or however.   Was there some reason the 12v power was 'the way to do it' back then?   The power bricks are cheap/reliable enough nowadays?

Geoff

Bryce

Quote from: P5ychoFox on 19:28, 22 February 18
Just hooked up a 10v 1.2A power supply and measure about 13v going through the power jack but zero volts are getting past the voltage regulator to the red and black wires on the white plastic connector that would normally be hooked up to the drive. Then I tried with a 12v 2A power supply and again got no output from the regulator.

Then the regulator is an ex-regulator. Someone probably connected the power the wrong way around for too long. Either remove the regulator an connect the 5V directly to the socket or (preferably) replace the regulator.

Bryce.

P5ychoFox

Just hooked the drive up to a PCW8256's internal drive power supply and the 3.5" drive did a quick click noise upon powering on the computer but that's it. No flicker of the LED or any other hum from it so I assume the drive is faulty. I'll give up with this external drive at this point. Many thanks for all the help.

tjohnson

If you used internal power connector does this have the 12v snd 5v swapped as per the 3" inch drive?  if so is unlikely it'll be compatible with the 3.5" and you may have fed 12v to the 5v input. Also is the software configured to use 3.5" i seem to recall you need a fid file to configure the drive.

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