KDSP2 - LED REMAINS ON

[G4BUE]

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.  I have checked U1, D3 and that the  
DSPx module is properly aligned, as suggested in the troubleshooting
section, and am now a bit puzzled - if there is a problem with the
LED, why does the filter appear to work ok?

Any help and suggestions will be welcome, please.

Thanks and 73 de Chris, W4/G4BUE


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[KK7P]

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)

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