scott@max.u.washington.edu (10/04/90)
One of my 1541 disk drives has a problem, and I would appreciated if someone out there could provide me with some info. The symtom is clear. There doesn't seem to be enough power getting to the board and the motor. The voltage across the 4700uf capacitor only reads 2volts and 1volt across the leads of the 7805. Also low reading appears across the CR3, only 1volt. I am suspecting that the CR3 is the culprite element since it appears this is the first element that the power coming out of the transformer goes through. But I don't know what exactly this element is or does. Does anyone out there knows what this element is or does. By the way this element is located on the corner when the leads from the transfer are connected (it is a black block like object). If you think that I am looking at the wrong place for the problem, could any give me some other clue to as what my problem is? I know with good amount of certainty that the 6800uf cap, 4700uf cap, 7805, and 7812 are all good. Any help will be greatly welcome. Sincerely, Scott K. Stephen
treesh@bach.helios.nd.edu (10/05/90)
And device called "CR" is proabaly a diode used in the rectifier stage of the power supply. If this is open, then the voltage will be low on the output. If this is shortted, then the voltage will be WAY to high, and proabaly blow the fuse, or worse! If you have an ohm meter, you can test this part by removing it, and then make an ohm check. In one direction it should read low (1-100 ohms) and the other should read high, like 10 times as much. ctfm
n8941063@unicorn.wwu.edu (stevens charles a) (10/05/90)
Now, I am not a computer technician, but I do know some electronics.
CR3, if that designation is correct, is a diode. If you truly suspect that
this is the problem, it is an easy thing to test. You will need a soldering
iron and an ohm meter (or doide/continuity tester). Simply desolder one side
of the diode, to remove it from the circuit. (it is not necessary to completely
remove the diode to isolate it, but you might want to if it is hard to get to.)
With the meter, check the continuity/resistance of the diode. It should
conduct with a very low resistance in one direction, and not conduct at all
(very high resistance) the other direction. (To change direction, just reverse
the meter leads.) If the diode conducts both ways, or doesn't conduct at all,
then the sucker's bad. It sounds as if it is open, from your description.
I hope this helps.
...Chaz...