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Profile Power Supplies
sigma7:
--- Quote from: pintoguy on May 17, 2025, 01:44:25 pm ---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.
--- End quote ---
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:
--- Quote from: pintoguy on May 20, 2025, 08:43:24 pm ---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.
--- End quote ---
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).
--- Quote ---learning how to do this with BLU and the Zilog Z8613 piggyback trick. Fortunately I happened to have one on my 10MB Profile.
--- End quote ---
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:
--- Quote from: sigma7 on May 25, 2025, 03:12:29 pm ---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).
--- End quote ---
Thanks. The problem happens with different boards, so I'm pretty sure it's the HDD
--- Quote ---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.
--- End quote ---
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
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