[Elecraft] KAT100 - Reluctant to come on, K2 often displays "not inst"

[Don Wilhelm]

Bill,

With that evidence, I would arbitrarily replace Z1.  Those 4MHz 
resonators are inexpensive.

73,
Don W3FPR

On 9/5/2018 2:42 PM, Bill Coleman wrote:
> OK, a final follow-up on this.
>
> Since the 12CTRL signal resulted in 5V power at the regulator immediately, I racked by brain trying to figure out why The KAT100 would fail to light the LEDs for seconds, sometimes tens of seconds.
>
> I decided the problem might have to do with the U1 clock. I put a scope probe on pins 13 and 14 of U1. While the KAT100 fails, these pins would float up to about 1 volt. When it worked, these pins would be at 0 volts, because the chip is sleeping! (the oscillator doesn’t run while the chip sleeps, to save battery power) So, it looked very much like the oscillator wasn’t starting reliably at power-on.
>
> I hit the Z1 resonator with a heat gun, with no immediate effect. Later I nudged Z1 with a screwdriver, and the KAT100 suddenly came to life. Not sure if I had a bad device, or just a bad solder connection, I re-flowed the solder connections to Z1 and to pins 12-14 of U1, where they connect.
>
> This seemed to work. I let everything cool down overnight, and checked it again in the morning. Oddly, the K2 was giving Info 080 and the KAT100 was failing again! I didn’t have time to diagnose.
>
> Today, however, the K2 powered right up, and the KAT100 snapped to attention, both working flawlessly.
>
> At the moment, I’m going to declare the mystery as being solved, and ignore the transient Info 080 issue. If it crops up again, I think I will replace Z1 on the KAT100.
>
>