Re: B&G Sonic Speed failure

Stefan Jeukendrup

Hi David,

Looks like  you found the document:

The red led not working means that somewhere in the "loop" there is a problem: (transmitter on Sonic speed board, transmit sensor, ultrasonic waves through the water, receive sensor, phased lock loop, Automatic Gain Control amplifier)

I guess you measured the internal power supply already, but did you measure AGC, is it between 1.8 and 2.5V?

Most likely  causes:

* something in the water path between the 2 crystals ( and that includes fouling and loose rubber caps although unlikely since your resistor values are good)

 * defecitive board, test by swapping with another one.

I have several Sonic speed boards if you need one to test.

Hope this is helpfull in some way.

Stefan Jeukendrup

sv Malaka Queen

SM2k #348 @ Newry Northern Ireland

Op 10-10-2021 om 10:30 schreef David Crisp:

Hi All,

The sonic speed on Wilna Grace has not worked for sometime so with the wisdom learned from this group I've been investigating.  Adjusting the spacing knob on the processing unit I'm unable to get the red light to come on. 
I have disconnected the transducer cables and tested them and all seems okay: - 111.4kΩ on one transducer and 111.7kΩ on the other which seems in tolerance and infinite resistance between all cables and the shielding.  Any advice on what I should check next?

David Crisp
SV Wilna Grace
Amel 54 #58

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