[Elecraft] KDSP2 - LED REMAINS ON

[Lyle Johnson]

Hello Chris!

> I have just built the KDSP2 and everything seems to work properly, 
> including the clock and changing the filter frfequencies.
> 
> However, the red LED remains on...

This is certainly peculiar.  If the DSP is working, the first thing it 
does is turns off the LED. This feature is controlled directly by the 
DSPx module, not the KDSP2 kit MCU.

Since the DSP appears to be working, I'd be suspicious of a short at the 
collector of Q4 or R13 on the KDSP2 kit portion.

You might try removing the DSPx but leaving the KDSP2 installed, power 
on the K2, and then *carefully*, using a spare resistor of 1K to 10K 
ohms, pull the end of R13 nearer J1 to ground.  This should cause the 
LED to extinguish.  If it does, the problem may be in the DSPx.  If not, 
the problem is in the KDSP2 circuitry associated with R13/Q4.

Another test is to use a voltmeter and probe P1 pin 4 on the DSPx.  The 
voltage should initially be around 3 to 3.5 volts, then drop to under 
0.5 volts.  When the voltage is at the lower level, the LED should be 
extinguished.

73,

Lyle KK7P

(who would have reponded sooner, but was in Germany last week)