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19 November 2015, 23:36
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#1 |
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tomead
Join Date: Feb 2010
Location: Chichester
Age: 45
Posts: 71
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A2000 rev 6.2 motherboard burns out u303
Hi,
This is my continuing story of trying to get my Amiga 2000 working. I have the original motherboard for the machine that has a odd problem. Last time it was powered up by me, I got a blank screen and the 74 logic at u303 burnt out due to a short I think. This board was sent away to have a new battery and a new kickstart socket fixed when I first got the computer. It burn out u303 the first power on when it came back. I sent it back when that happened, and have just had it returned after 10 months with the fault not corrected. At present the moment u303 is socket, as it has been replaced 6 to 8 times whilst diganosing the fault. The board now has the transistor at u302 removed, which I have and the resistor at R902 disconnected at one end. Two questions. Anyone have an idea what is wrong ?, and anyone willing to have a go at fixing it. Trying to save board as it is in good physical condition, and had very little battery leakage when I got it. Last edited by tomead; 20 November 2015 at 00:34. |
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20 November 2015, 05:18
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#2 |
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Registered User
Join Date: Sep 2009
Location: San Antonio, TX USA
Age: 50
Posts: 1,184
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I would get a data sheet for the chip and verify that the power input is at correct voltage.
Also, verify that the INPUT voltages do not exceed the allowable tolerances. So, it looks like it's a AND gate chip, so max input is 7V and 4.5V to 5.5V recommended. |
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20 November 2015, 21:24
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#3 |
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Registered User
Join Date: Jun 2010
Location: PL?
Posts: 2,741
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DMM in hand and check all pins for dangerous voltages...
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11 September 2016, 16:05
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#4 |
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tomead
Join Date: Feb 2010
Location: Chichester
Age: 45
Posts: 71
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Hi, I am bumping this thread, as this broken computer is tempting me to throw everything in the bin, so I am am asking again if anyone in the uk would be able to have a look at the motherboard. I also have another rev 6.2 board, which i think is in an unreapairable state, which would be a gift to anyone who would be willing to look at and fix this board.
Last edited by tomead; 11 September 2016 at 19:18. |
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11 September 2016, 16:36
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#5 |
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Ya' like it Retr0?
Join Date: Jul 2005
Location: United Kingdom
Age: 49
Posts: 9,768
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@tomead
take some hi-res pictures my friend, I will have a look and hit the schematics tonight about the U303 - I remember an older 5.3 board that had a similar issue. If its a simple trace and fix I might be able to help, sadly my time is very pressed with work lately so sadly I don't have the opportunity to say "chuck in the post" - but I will have a scout with the schematics I have here if its under a couple of hours work I may be able to fit this in on a weekend =) better that than you throwing it away sir! |
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11 September 2016, 19:26
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#6 |
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tomead
Join Date: Feb 2010
Location: Chichester
Age: 45
Posts: 71
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Thanks Zetr0 for the possible offer. Here are some pics of the important areas of the board. Let me know if you need pics of other areas of the board.
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