External PSU for CD Drive

wiz12 · 24 April 2018, 12:08

I have an external IDE CD Drive connected to my Amiga's blizzard SCSI port. The drive has an acard 7720u SCSI to IDE adapter and it's powered using an ATX PSU via a molex connector and everything is working great though I'm wondering if there would be any better solution to powering this drive rather than using this bulky psu which can take up a lot of space?

kgc210 · 24 April 2018, 16:23

I use this to power my CD32 with an adapter.
https://www.ebay.co.uk/itm/320705061192

It's designed for HDD / CD.

wiz12 · 24 April 2018, 17:48

I actually have that exact same psu as I got it for this purpose but unforunately the CD drive doesn't like it or work right when connected to it. For some reason the drive won't spin up fully and the psu makes a high pitched noise, it's almost as if that psu can't provide enough juice to the drive?

kgc210 · 24 April 2018, 18:19

It might be down to grounding, there is only one ground pin on the molex connector on the PSU. Try a molex extension and join the two grounds together?

wiz12 · 24 April 2018, 18:53

It's not a standard molex cable though, the Acard adapter instead uses a molex + floppy to molex Y cable. I'm guessing the molex connector supplies +12v and the floppy connector +5v. Can I test this cable for grounding issues?

kgc210 · 24 April 2018, 19:45

That PSU I linked to only has one ground.
Normal molex has two grounds (the two black cables) so you might need to bridge them for your CD drive to work.

wiz12 · 24 April 2018, 20:19

I bridged the two grounds together on the molex connector but unforunately the problem remains with the high pitched PSU noise and the CD drive not working.

Daedalus · 25 April 2018, 10:00

It might be that the CD drive isn't drawing enough current to regulate the PSU properly. A similar issue can happen with Amigas themselves powered from ATX PSUs. The direct fix is to increase the load, either by adding more gear (a few hard drives), or a dummy load built from some heavy duty resistors.

In reality though, an ATX PSU isn't intended for such small loads, especially since an optical drive uses practically no power at all when it isn't spinning the disc or opening/closing the tray. The common response these days is to use a small, efficient industrial PSU module like a Meanwell or similar. You could also power the Amiga itself with that if needed. Such models are typically cheaper than an ATX supply, though will require an enclosure and some DIY.

wiz12 · 25 April 2018, 12:05

I am currently powering the Amiga using a Meanwell 65W PSU housed in the old PSU casing, I guess I could tap into that with a molex cable and it should work, it's definitely an option to consider. I have seen small PSUs on eBay like this, I wonder would one of these be correctly rated to work for the sole task for powering a CD drive correctly?

Daedalus · 25 April 2018, 12:36

Ah, yes if you're already using a Meanwell PSU, by far the simplest option is to add another output on that to provide power for drives. For neatness you could even add a Molex connector to the PSU casing, so that the cable to the CD-ROM can be removed when not required.

The PSU you linked to appears to be a single output module, so you would choose 5V *or* 12V. A full-sized CD-ROM drive typically requires both. Anyway, they generally look like overkill for a drive that which probably uses 2 or 3 watts at most.

wiz12 · 25 April 2018, 14:47

Yes, I think it's the best option and should be straightforward to add a molex output. Thanks Daedalus.

24 April 2018, 12:08	#1
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 752	External PSU for CD Drive I have an external IDE CD Drive connected to my Amiga's blizzard SCSI port. The drive has an acard 7720u SCSI to IDE adapter and it's powered using an ATX PSU via a molex connector and everything is working great though I'm wondering if there would be any better solution to powering this drive rather than using this bulky psu which can take up a lot of space?

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24 April 2018, 16:23	#2
kgc210 Registered User Join Date: Jun 2016 Location: Stoke-On-Trent, England Posts: 450	I use this to power my CD32 with an adapter. https://www.ebay.co.uk/itm/320705061192 It's designed for HDD / CD.

24 April 2018, 17:48	#3
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 752	I actually have that exact same psu as I got it for this purpose but unforunately the CD drive doesn't like it or work right when connected to it. For some reason the drive won't spin up fully and the psu makes a high pitched noise, it's almost as if that psu can't provide enough juice to the drive?

24 April 2018, 18:19	#4
kgc210 Registered User Join Date: Jun 2016 Location: Stoke-On-Trent, England Posts: 450	It might be down to grounding, there is only one ground pin on the molex connector on the PSU. Try a molex extension and join the two grounds together?

24 April 2018, 18:53	#5
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 752	It's not a standard molex cable though, the Acard adapter instead uses a molex + floppy to molex Y cable. I'm guessing the molex connector supplies +12v and the floppy connector +5v. Can I test this cable for grounding issues?

24 April 2018, 19:45	#6
kgc210 Registered User Join Date: Jun 2016 Location: Stoke-On-Trent, England Posts: 450	That PSU I linked to only has one ground. Normal molex has two grounds (the two black cables) so you might need to bridge them for your CD drive to work.

24 April 2018, 20:19	#7
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 752	I bridged the two grounds together on the molex connector but unforunately the problem remains with the high pitched PSU noise and the CD drive not working.

25 April 2018, 10:00	#8
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	It might be that the CD drive isn't drawing enough current to regulate the PSU properly. A similar issue can happen with Amigas themselves powered from ATX PSUs. The direct fix is to increase the load, either by adding more gear (a few hard drives), or a dummy load built from some heavy duty resistors. In reality though, an ATX PSU isn't intended for such small loads, especially since an optical drive uses practically no power at all when it isn't spinning the disc or opening/closing the tray. The common response these days is to use a small, efficient industrial PSU module like a Meanwell or similar. You could also power the Amiga itself with that if needed. Such models are typically cheaper than an ATX supply, though will require an enclosure and some DIY.

25 April 2018, 12:05	#9
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 752	I am currently powering the Amiga using a Meanwell 65W PSU housed in the old PSU casing, I guess I could tap into that with a molex cable and it should work, it's definitely an option to consider. I have seen small PSUs on eBay like this, I wonder would one of these be correctly rated to work for the sole task for powering a CD drive correctly?

25 April 2018, 12:36	#10
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	Ah, yes if you're already using a Meanwell PSU, by far the simplest option is to add another output on that to provide power for drives. For neatness you could even add a Molex connector to the PSU casing, so that the cable to the CD-ROM can be removed when not required. The PSU you linked to appears to be a single output module, so you would choose 5V or 12V. A full-sized CD-ROM drive typically requires both. Anyway, they generally look like overkill for a drive that which probably uses 2 or 3 watts at most.

25 April 2018, 14:47	#11
wiz12 Registered User Join Date: Feb 2017 Location: Ireland Posts: 752	Yes, I think it's the best option and should be straightforward to add a molex output. Thanks Daedalus.

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