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Guest hiteja

FSBUS FLASHING HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Hello,I have just made the fusbus key, display and com boards and neither the key nor dispay will flash. I keep getting the read after write failure. I have checked for broken traces and such but have found none. I have measured the voltage on the "MCRLR" pin and am getting 7.09 volts instead of the required 13.5...what could casue this? I noticed that the transistor on the com board heats and cools randomly. How do I check if the required voltage is being supplied for flashing. IF ANYONE HAS THE HEX FILES FOR FLASHING, COULD YOU SEND THEM TO ME?Thanks for any help,Jason

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Hi Jason.Check your boards again, very carefully, using as much magnification as possible. 99.9% it's either a broken route, a tiny ichy ######y tiny winnie short-circuit or cold soldering.Check that you have put the capacitors with the correct polarity.If you are measuring below 12V on that point, there must be a short circuit somewhere in the line. Also, try not connecting all the boards at the same time. This way you may locate the board with the problem.You can also search this forum for more ideas. This subject has been discussed zilions of times and you will find a lot of interesting threads.Good luck!George DorkofikisAthens, Greecehttp://www.precisionmanuals.com/images/forum/betaimg.jpg

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Well I went home an tested everything I could without an ocilliscope and found that my power supply is giving 12 volts eventhough it says 9 volts. Could this be the problem...I am still getting onlt 7 volts at the mclr pin on the pic and 13.5 volts after the transistor on the com board.ThanksJason

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>Well I went home an tested everything I could without an>ocilliscope and found that my power supply is giving 12 volts>eventhough it says 9 volts. Could this be the problem...I am>still getting onlt 7 volts at the mclr pin on the pic and 13.5>volts after the transistor on the com board.>>Thanks>>JasonI am using a PC AT power supply to push 12 volts to FSBUS and it works okay. Just needs a heatsink to the regulator (the chip with 3 long legs)//Tuomas

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Jason,What kind of Power supply are you using? If's it not stabilized then it may be the cause of the problem.The 13V are obtained from the 555 IC which is feeded by the 7805 IC Regulator with stabilized 5V. BUT, the 7805 needs an input of at least 7.5V to give a stabilized 5V output.If you are measuring the Power supply output to be 12V but rated for 9V, then it's definately not stabilized, so when the load it connected, it gives less than 9V output. Try measuring the voltage exactly at the supply points on the COM board with all the concerned boards connected.If you get less than 8.7V you have a problem.The best way would be to build a stabilized 9V/1A power supply. It's very easy and requires just a tranformed (of course), a rectifier, 3 capacitors and 1 7809 IC regulator. For more power you will need to use a power transistor, but I don't think you will ever need more than 1A for FSBUS!Also, did you attach a heatsink on the 7805 regulator? It can get pretty hot on full load and the heatsink is mandatory.Regards,George DorkofikisAthens, Greecehttp://www.precisionmanuals.com/images/forum/betaimg.jpg

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