[time-nuts] PRS10 Lamp Module Needed

[Vasco Soares]

Hi Bruce,

Thanks for your reply.

I'm aware that the tantalum capacitor is on of the weak points of the RF 
amplifer that excites the lamp. After testing the unit and using the 
monitoring software available I found that the problem relies on that 
specific part of the circuit. In fact the RF unit was burned like the 
tantalum capacitor you are refering. Last year I rebuild that circuit 
section interely with high quality components with good temperature 
reliability replacing the RF transistor, porcelain capacitors and metal film 
resistors. The lamp was heated up as well. The unit worked for about 6 
months. Now I found again that the signal strenght received by the photocell 
has droped below the acceptable value so there is no more I could do except 
to send it back to SRS for lamp replacement...

Regards,
Vasco Soares


----- Original Message ----- 
From: <brucekareen at aol.com>
To: <time-nuts at febo.com>
Sent: Wednesday, August 13, 2014 3:21 PM
Subject: [time-nuts] PRS10 Lamp Module Needed


> Vasco,
>
> As Brooke said it is unlikely there are spare PRS10 lamp modules found 
> outside the manufacturer.  The probable reason is that when the PRS10 
> units are assembled certain adjustments to the firmware are necessary such 
> as the starting level and final bias of the FET oscillator transistor.  As 
> far as I know, SRS has not revealed how to access to these factory 
> settings.
>
> It might be possible to repair your lamp assembly.  One point of failure 
> is the Tantalum capacitor found in the lamp assembly.  Another possibility 
> is that the heater resistor may have changed value or opened.  Although it 
> looks daunting, it is possible to replace the FET power transistor; 
> however, after replacing the transistor in one unit, I found the 
> transistor's characteristics were a little different than the original and 
> the operating parameters were not right.  I considered adding some 
> external resistors to shift the biasing, but finally decided to try 
> another transistor with somewhat different characteristics.  But in this 
> second try I damaged the board.
>
> If the rubidium bulb assembly is suffering from old age, it might be 
> possible to improve it with a heat gun as discussed on this listt several 
> times in the past.  The bulb is cemented in place, but it might be 
> possible to remove and replace it.
>
> Bruce, KG6OJI
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