Scott, The microprocessor (Control Board U6) chip will not stand a lot more than 5 volts without damage. The application of 8 volts on the 5 volt rail could have damaged any of the digital chips on the control board - those are U6, U7 and U8.
Many devices on the RF board receive the power from the 8R and 8T lines - and must have the RX or TX signal active from the microprocessor to apply voltage to 8R or 8T (if the uP is bad, some power to the RF board will not happen). Make a quick check - power on and check the voltage out of the regulators (5V and 8V), check power to U6 at pin 1 (should be 5 volts), then check the RX output (U6 pin 28) which under normal conditions should be 5 volts during receive (I expect you will find it at zero volts). If RX is not 5 volts in the above test, obtain a new microprocessor (U6) and while you are ordering replace U7 and U8 as well - they have been stressed and if they are not bad now, they could fail later. The other components on the Control board should have survived just fine because they are analog devices and have higher voltage ratings whereas the digital logic circuits can be damaged with voltages above 6 volts. 73, Don W3FPR > -----Original Message----- > > I finished assembling K2 # 5846 a few days ago and have a problem > that I need some help on. > After finishing the initial alignment I could hear signals on several > of the bands and had transmitter output. During the final alignment > the display started burning too bright. I found a solder bridge on > the J7 connector that was shorting the outputs of the 8 volt and > 5 volt regulators together. This was causing both regulators to be > putting out 8 volts. I cleared this up and was proceedng with the > alignment when I notice that U6 on the control board felt warm and I > had lost voltage on most of the components on the RF board. > I turned the rig off for a couple of hours and when I tried to turn > it back on, it wouldn't power up. I checked F1 and it has 12.8 > volts on both pins. > Anyone have any ideas? > Scott N5SM > -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.16.0/610 - Release Date: 12/30/2006 2:59 PM _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
