[Elecraft] K2 Assembly Problems

[Don Wilhelm]

DW,

First, the 7808 will work, but the stock regulator is a low dropout 
type, so if you replace it with a 7808, the power supply voltage that 
will create proper operation will have to be a bit higher.  That may 
make no difference if you are operating from a home station power 
supply, but if you are operating from a battery, the battery low voltage 
that will cause improper operation will be higher than with the low 
dropout regulator.  I suggest requesting a replacement regulator from 
Elecraft - parts at elecraft.com.

The low 8 volt supply voltage will not cause an MCU failure - you have a 
different problem there.  Check the component values and check the 
soldering.  When you are finished, check the soldering.

73,
Don W3FPR

DW Holtman wrote:
> Hello,
>
> I posted this a few days ago. I will cut and paste here again.
>
> ""I'm in the middle of building a K2, S/N 6412.
>
> While doing the Alignment and test Part 1, I had a couple of readings that 
> were not in specs.
>
> 1. Page 48, Setting the AGC Threshold, the manuals calls for adjusting  R-1 
> for a reading of 3.80VDC on pin 5 of U2. The highest R1 would adjust to is 
> 3.60VDC.
>
> 2.  Page 48 Bargraph Current test. The manual calls for a current reading of 
> 0.16 to 0.18. My K2 reads 0.25 amps. That is quite a bit higher than what is 
> called for.""
>
> I received suggestions to check the voltage on the 8 volt regulator in the control board. It is just as suggested, the voltage is almost 1/2 volt low. Will a 7808 work? Is it the same as a LM2930T-8? They  both have the same NTE cross reference and are available locally.
>
> I finally got around to reassemble for alignment part II. Some times, when it turns on, nothing happens, no display on the LCD, none of the controls do anything. After I turn it off and on a couple of times, it starts working as it is suppose to. This also happened in the first section for alignment where I had the problems listed above, I thought it was the memory initializing. This is not the case, it is still doing the same thing. Would the low 8 Volts cause the MCU to hang up?
>
>
> Thank you for your help.
>
> Best,
> DW Holtman
> WB7SSN
>
>
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