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+--- Thread: [TG] [TG11] A78 7" MFD wifi - failing to detect transducer (/showthread.php?tid=8759)
[TG11] A78 7" MFD wifi - failing to detect transducer - dmac68 - 07-03-19 02:28 AM
Hello
My A78 as above has not detected my transducer since a rough trip home a few weeks back. There is no damage on the transducer, no water leaks out after a trip, no marks on it and it didn't even kick up at any time. The MFD was playing up as well by roving with all the heaving and the boat icon appearing top left screen indicating it had lost its way (an annoying issue with these touchscreen units in wet/rough weather). No water got into jacks at the back of MFD and there are no known or observable cable issues from transducer up to MFD. I have the supplied suppressors at the rear of the unit and have had them installed there for over a year. The system has less than 300 hours running time on it.
I have done the soft reset not affecting all data and now also the full reset having first transferred my data to an external SC card first (as per advice on a similar post). The unit fires up properly, I reinstall all my settings then select fishfinder on the homescreen, it loads and it says 'no transducer' or similar. I press 'select transducer' as offered but it does not find one and none appears in the list.
I don't want to buy a new transducer to 'test' if it is the old one that is kaput. I will be months before I can remove the transducer and travel to civilisation to have it tested at a shop - I am in the remote South Pacific. I am relying on my 20 year old other brand fishfinder at present - I run second/redundant systems in nav, comms, depth/fish finders, EPIRB's etc due to my remote location - there is no Coast Guard out here!
Thanks
Darren
RE: [TG11] A78 7" MFD wifi - failing to detect transducer - Tom - Raymarine - Moderator - 07-16-19 04:55 AM
Hello Darren,
Sorry you've not had a reply before.
The a78 detects the presence of the transducer using a simple 'sense' resistor. The value of the resistor denotes what class of transducer is connected. Because the measurement is so simple, it's normally very reliable.
We have seen sense resistance measurements fail because of electrical noise on the power supply or transducer cabling: in one memorable instance I dealt with, the owner found that his system consistently worked at low speeds but always reported no-transducer once he got above about 5 knots. The cause was very noisy charging voltage from his outboard, and when run off a separate house battery everything worked perfectly. It's worth, then just checking whether the system does the same on an independent battery if possible.
If it does then the next step would be to measure the resistance of the 'sense' line in the transducer cable, and if that checked out ok then perhaps something is making a poor contact inside after that rough trip home. That shouldn't happen and I don't recall coming across it before, but of course anything's possible.
I'll send you the transducer sense resistance check details tomorrow, but if this and the independent battery test check out then I think that you'd need to get the display checked, I'm sorry to say. We have a network of Service Dealers in the bigger population centres around the coast, and a service centre in Sydney.
Regards,
Tom
RE: [TG11] A78 7" MFD wifi - failing to detect transducer - Tom - Raymarine - Moderator - 07-16-19 11:35 PM
Hello Darren,
As promised.
The CPT-100 / CPT-DVS transducer 'sense' resistors are 10kOhms (10,000 ohms) between pins 4 and 5 of the transducer's connector, as shown in the attached pin-out drawing. Let me know if you're having trouble making this measurement or to check your results.
Regards,
Tom