[time-nuts] LPRO-101 Status

[iovane at inwind.it]

On July 25, 2009 don.key at ntlworld.com wrote

>The second one would not lock within 15 minutes, so I returned it (to China) 
>for a replacement. As I didn\'t have a heatsink, I didn\'t want to leave it 
>any longer. Besides, if it doesn\'t lock within 5 minutes, then I assume it 
>is faulty. Instead of the frequency sweeping up & down, the Xtal volts 
>started at around 6V2, then swept down to 0V & stayed there, leaving the 
>frequency about 180Hz low, as seen on a HP 8591E analyzer.

>Out of interest, did your unit sweep up & down, or was it similar to mine?

I had exactly the same problem with one of my units, but fixed it.
In LPRO the voltage starts sweeping around 6.2V and goes up and down between 
two preset limits (about 0.5V and 12.5V) until lock occurs. 
Comparator circuits do sense the crossing of voltage limits and 
invert sweeping. Depending on what comparator fails, the unit remains 
in deadlock around 0V or 14.3V.
I have had both cased with two units.
In the case of 0V the faulty component was resistor R230 (100K, bottom of pcb).
It reads onboard about 23K when faulty and about 18K when good. Replaced R230, 
the unit now works.
In the case of 14.3V the faulty component was R215 (100K, bottom of pcb). 
It reads onboard >1Mohm when faulty. Replaced it, and the unit works.

I have several LPRO, and all of them do lock in about 3.5 mins at ambient
temperature of 20 °C or so. I use heatsinks.

Bye,
Antonio I8IOV