Re: Faulty disk drive in 9114B ? Message #7 Posted by inaki on 8 Dec 2009, 6:06 a.m., in response to message #6 by Vieira, Luiz C. (Brazil)
Thanks for your thoughts guys!
After checking everything I checked the power by measuring the current the unit takes when in standby mode, when using logic commands without resource to disk, and finally when using commands that involve the disk.
When the 9114B is in standby mode or receiving commands that do not involve the disk it takes a small amount of current. But when the disk drive is involved the current taken raises a lot, up to 1,5A (in my measurements, but probably is higher than this).
After reading the Luiz message I decided to replace the battery with a regulable lab power supply. I started with 7.3V and 1A, just not enough to feed up the disk drive. The symptoms were exactly the ones mentioned in my first message. Then I raised the lab power supply limit to 2A.
And voila, the disk drive started to work! The initial startup test was performed as expected with the heads moving up and down. The led on the front of the disk drive was alive!.
It was the time to test commands from my 71B. Bingo! I was able to initialize the diskette!
So my guess is that Luiz put the hammer in the nail here. The battery may be good enough to feed the logic but not enough to feed the disk drive in every work, even when the 3 leds in the front show full battery.
As a side comment. If ones tries to use a power supply that bypasses the battery as I did for the tests, it must be a power supply able to raise current to about 2A (for about 7.5V). I tried to use some higer voltage, up to 9V, without problem. However it would be mandatory to check the power regulators specifications to see whether it is wise to use a higher voltage power supply.
As I could see for this case, and others related to 9114B in this forum, it seems a bad battery can cause a lot of trouble.
Thanks for your help!
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