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[pintoguy]

I've been fighting issues with two power supplies on two of my Profile external hard drives. I would consider myself as low-to-medium savvy when it comes to electronics, and I'm hitting my head trying to solve these problems. I might ask for help at some point here, but out of curiosity, I started to look for a modern replacement to these power supplies (ASTEC Models AA11770A and AA11771). Turns out that you can buy a new one (Model PT-65B) for ~$20. It's a 65W, +5, +12,-12V PS which should do the trick I think. I checked that both my controller card and HDD work, and it should be doable to insert this smallish PS in the existing enclosure. Has anyone tried a complete PS swap ? Do you think it would affect the Profile resale value negatively ?

Thanks in advance

[sigma7]

I'd expect that anyone wanting to actually use a ProFile will prefer to use an emulator rather than the original spinning disk, so whether to replace the PSU to restore operation of an original is a good question.

If one wants to use the enclosure for an emulator, then the PSU requirements are much less, so one might choose a different replacement.

Not being knowledgeable regarding collector value; I assume original parts would be of greater value to a collector, and to some collectors a non-working original PSU might be much more valuable than a working replacement PSU (I don't really know).

On the other hand, demonstrating the HDA and controller are in working condition would strongly affect the value, which means either installing a working PSU or configuring a temporary setup.

If the PSU is replaced, I suppose one could include the original non-working PSU so that a collector could restore if desired.

The conundrum is resolved if the original can be repaired.

So there are some not-very-useful thoughts... maybe the answer is more obvious to someone else?

[pintoguy]

OK so I got my new $20 power supply and installed it (see before and after pics below). All 3 voltages (+5, +12, -12V) are right on the money. I wasn't too sure what to do with the "AC OK" input to the Profile PCB, but my understanding is that it's high +5V when the PS is working OK. So I fed the +5V line to it.

After all this, my Profile works very sporadically. Sometimes the LED starts solid yellow and nothing else happens, sometimes in stays yellow for a very short moment (perhaps 100ms) and nothing happens either, and sometimes it works normally: it flashes yellow for 1/2 second or so, and then proceeds with the normal self test after ~20 seconds. During self-test, the LED blinks at every track, and goes solid yellow when it's done, indicating that the drive is ready. Oh, by the way, I checked with a working Profile that both the controller and the HDD work OK.

So I suspect that the "AC OK" signal needs to be delayed a bit after the PS is turned on. I read reports that it is done to protect the board from initial voltage surges. Can anyone confirm that, or help in any way if I'm wrong. And if it's the case, how can we mimic this "AC on" signal with a short delay (say 500ms) from the +5V line ?

Thanks in advance

[pintoguy]

I'd expect that anyone wanting to actually use a ProFile will prefer to use an emulator rather than the original spinning disk, so whether to replace the PSU to restore operation of an original is a good question.

If one wants to use the enclosure for an emulator, then the PSU requirements are much less, so one might choose a different replacement.

Not being knowledgeable regarding collector value; I assume original parts would be of greater value to a collector, and to some collectors a non-working original PSU might be much more valuable than a working replacement PSU (I don't really know).

On the other hand, demonstrating the HDA and controller are in working condition would strongly affect the value, which means either installing a working PSU or configuring a temporary setup.

If the PSU is replaced, I suppose one could include the original non-working PSU so that a collector could restore if desired.

The conundrum is resolved if the original can be repaired.

So there are some not-very-useful thoughts... maybe the answer is more obvious to someone else?

Thanks @sigma7. This somehow mirrors my thinking as well

[pintoguy]

So I confirm that the timing of the "AC OK" signal is critical during power on of the Profile. This signal should be grounded for about one second, which keeps the LED light "on". After one second or so, it could be either open or fed with +5V, at which moment the controller starts the initialization, with the LED "off" for about 20 seconds before the disk scan. I have a small relay on order and I hope I can mimic a one second time constant with a simple RC line.

[sigma7]

So I suspect that the "AC OK" signal needs to be delayed a bit after the PS is turned on. I read reports that it is done to protect the board from initial voltage surges. Can anyone confirm that, or help in any way if I'm wrong.

Looking at ProFile controller and drive board schematics, as far as I can tell, when the PowerOK signal is low, it:

• Disables write current to the heads
  
• Holds the Z8 microcontroller in the Reset state
  
• Resets the address counters for the DMA memory used for transfers to/from the host
  

Also, the CRES reset signal from the host just pulls PowerOK low, so evidently the signal functions as reset in general.

I speculate the design intent of PowerOK in this case is to prevent erroneous writing to the disk when the circuitry doesn't have sufficiently reliable power to operate correctly, and doubles as a power-up reset.

So I'm wondering if there is something about the original PSU's (or that specific replacement PSU's) output sequencing that creates the need to hold PowerOK false... interesting.

[pintoguy]

Yes, most likely. Thanks for your insight. By the way, my monkeying around with this power supply and the lack of power-on control might have led to faulty write events in my HDD, as your rightfully suggested. I'm afraid I now need to do a LL format to clean up the disks, as the HDD does not come ready any longer.

Thanks to this board, I am now learning how to do this with BLU and the Zilog Z8613 piggyback trick. Fortunately I happened to have one on my 10MB Profile. Jut need to find out how to do it.

I might bug this forum again if I need help.

Thanks !!

[sigma7]

I'm afraid I now need to do a LL format to clean up the disks, as the HDD does not come ready any longer.

IIRC, the ProFile controller board has a reputation for developing a bad contact causing this sort of symptom. The solution may be as simple as reseating the socketed chips on the controller (ie. pry both ends of each chip slightly out of the socket, and optionally push them back in).

learning how to do this with BLU and the Zilog Z8613 piggyback trick. Fortunately I happened to have one on my 10MB Profile.

IIRC, the Z8 piggyback comes in 4k and 8k variants (or is it 2k and 4k?); the 10 MB ProFile uses the larger variant, while the 5MB ProFile uses the smaller variant. I believe one can use the larger variant in the 5MB ProFile, but the ROM needs to be adjusted to suit.

Good luck!

[pintoguy]

IIRC, the ProFile controller board has a reputation for developing a bad contact causing this sort of symptom. The solution may be as simple as reseating the socketed chips on the controller (ie. pry both ends of each chip slightly out of the socket, and optionally push them back in).

Thanks. The problem happens with different boards, so I'm pretty sure it's the HDD

IIRC, the Z8 piggyback comes in 4k and 8k variants (or is it 2k and 4k?); the 10 MB ProFile uses the larger variant, while the 5MB ProFile uses the smaller variant. I believe one can use the larger variant in the 5MB ProFile, but the ROM needs to be adjusted to suit.

Yes., from what I read is 2k for the 5MB and 4k for the 10MB. I have the 4k. People have been succesful LL formating a 5MB with the 4k chip, but I need to read all the details. I have a EPROM programmer on order