Re: Modern replacement power supplies for Apple ProFile hard drive?

Sorry for the posting flood. I'm basically using this list as a vehicle to think the process through, and maybe one of you can catch a mistake before I do something really stupid.

With that, I found out in the ProFile service manual that the AC signal is actually a POWER OK signal.

"The supply also contains monitoring circuitry to detect a power failure. This monitoring circuitry senses a power failure before the internal DC voltages drop. If a power failure should occur the monitoring circuitry uses a signal called POWER OK (POK) to reset the Z8 on the controller board. This allows the intelligent controller in the ProFile to prevent any data loss if the power fails or is turned off accidentally. The system will not begin any operation until the power is on for at least one second. Once a failure is detected, the head current is shut off to prevent the accidental writing of false data that would otherwise occur if a write operation were to process when the power failed. The power supply is completely shielded to eliminate the effects of electro magnetic radiation."

So, with that behind me, I Googled around to see exactly what kind of signal POK provides. Fortunately, AT and ATX power supplies provide a "power good" signal.

http://en.wikipedia.org/wiki/Power_Good_Signal

According to the Wikipedia article, the signal is basically +5V DC. I'm thinking then why can't I just connect the AC line to the +5V DC? The only reason I can think of not doing this is that, according to the Wikipedia article, a controller will wait until the power supply reaches capacity before it starts to run the processor. So, an AT or ATX power supply is designed to send the +5V DC POK signal ONLY after up to 0.5 seconds or whenever the power supply is running at 100-percent. In other words, if I connected the AC line directly to the +5 DC, it won't have the 0.5 sec delay, and I'm risking the hard drive from shutting down too soon.

In a nutshell, I won't be able to use the 50W power supply after all. I'll need to continue searching for an AT power supply that is small enough to fit into the original power supply chassis. I'm learning quite a bit about power supplies in such a short period of time!

On Sun, Dec 22, 2013 at 10:08 PM, Bryan Villados <groink1_at_email.domain.hidden> wrote:

> I'm getting closer... I just discovered that I have a power supply that
> "almost" meets the criteria I need. It has the right +/-12VDC and 5VDC, and
> it is 50 watts - more than I need. It is a working pull from a Cisco 2600
> series router I recently stripped. I want it to be low in watts so that I
> don't have to run a fan.
>
> The only problem now is that the ProFile's power supply provides an
> additional "AC" line to the controller board. This AC line provides a
> signal to the controller board, basically telling it that the mains power
> is working. If the mains were to shut off, there is enough power stored in
> the capacitors to allow the controller board to power the ST-506, empty the
> cache to the hard drive, and then properly shut down. Unfortunately, the
> power supply I found doesn't provide this. As a matter of fact, I don't
> think "any" power supply does this. This is something that was special to
> the ProFile. I'm not even sure if the Apple Lisa II's power supply did this
> for the internal widget drive.
>
> What I'll need to do then is research exactly what kind of a signal this
> AC line actually provides. Maybe I can create this signal using an Amtel
> microcontroller. I'm assuming it is probably a digital signal (on or off)
> or an analog signal with a certain amount of resistance being sent through
> it while the mains is running.
>
> Time to read through more of the documentation that was sent to me.
> Hopefully there's something in there that talks about the AC line.
>
>
> On Sun, Dec 22, 2013 at 3:28 PM, Bryan Villados <groink1_at_email.domain.hidden> wrote:
>
>> Wow! A lot of stuff to pour through. Thanks everyone for the attachments!
>>
>> What it basically comes down to is:
>> - The power supply needs to handle 115V or 230V, 35-watts, and can
>> deliver +/- 12VDC and +5VDC.
>>
>> - Whatever replacement power supply I get, I'll have to get the correct
>> pin-outs for the two internal power connections. Not a problem since the
>> power supply has the wires nicely silkscreened onto the PCB.
>>
>>
>> On Sun, Dec 22, 2013 at 2:26 AM, Bryan Villados <groink1_at_email.domain.hidden>wrote:
>>
>>> I have two Apple ProFile drives, both of which have the 115/230V power
>>> supplies. Both have blown the same capacitor - the 0.1 microfarad capacitor.
>>>
>>> Rather than trying to replace all the caps in these power supplies, I'm
>>> hoping that there are more modern power supplies out there that I could use
>>> to replace the Apple ProFile power supplies. I'm looking for one that can
>>> fit internally, and should be able to fit in the same power supply cabinet
>>> as the original, as the controller board mounts on top of the power
>>> supply's chassis.
>>>
>>> The power supply supplies +5VDC and +/-12VDC. There are two power
>>> connectors: one connects to the hard disk drive, and the other connects to
>>> the controller board. Reading the service manual, the power cable that
>>> connects to the controller board is used so that the controller board can
>>> detect loss of power, so that it minimize data loss that might have been
>>> still stored in the controller board's memory.
>>>
>>> Thanks!
>>>
>>
>>
>

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