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Old 26-02-2015, 20:42   #16
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ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: M802 SSB not transmitting

Karen,
Yes, this is an old thread, and it might've been better to start a new thread, to attract a detailed response....but we are here, so let's see if we can solve this problem and get 'ya back on-the-air!



1) First off your location is listed as "Melbourne Australia but not there now!", please let us know where you / your Icom M-802 is actually at now....So, we can give you some real-world advice on testing/evaluating things...


2) Secondly, please let us know if you are receiving signals normally / regularly???
(and be sure to clarify that the radio IS actually going into "transmit", the "TX" indicator shows on the display...)

All below info/advice is making the assumption that:
a) you are somewhere that you receive signals well...
b) you are currently receiving signals well...
c) the radio is going into transmit....


Knowing these first 2 or 3 things will go a LONG way in helping us help you....
So, PLEASE answer these questions first, before you proceed with further troubleshooting...




3) A simple DC voltmeter check of the "13.6vdc" power pin on the tuner control plug on the back of the M-802 will tell you right away if the radio is supplying sufficient power for the tuner....
Pin 3 is "+13.6vdc" (or actually whatever voltage the radio is being supplied), red wire on the tuner control cable...
Pin 4 is "negative", black wire on the tuner control cable...

(there are other voltages/pins, but do NOT mess with them, not yet anyway!)

If you get no voltage here, then the M-802's internal 5 amp fuse is most probably blown....and before you replace it, be sure to find the reason it blew (such as bad wiring, etc.)....



4) Next, checking all connections is very important here, as unless you took a lightning strike, or subjected the M-802's 12vdc power wiring to a higher voltage (higher than 16vdc continuous or higher than 18 volts for even a short spike), etc. the M-802 is a very reliable piece of kit, as is the AT-140....
(understand that the M-802's PA, like ALL hi-current "12vdc" devices are NOT switched on/off by a switch, but rather is wired directly to the 12vdc power connector all the time....so if you had someone working on the electrical system on-board and they screwed-up, even just for a split-second, they may have blown some components in the M-802's final PA unit...this IS repairable, but typically not in remote 3rd world cruising areas without shipping the radio back to a 1st world Icom repair center...
Anyone with a "24vdc boat", needs to be VERY careful when working with on-board electrical stuff....)


But, please understand that the coaxial cable connections are also very important here!!!
Especially true for the symptoms that you describe, as if the AT-140 does have power, but you have a shorted-out coaxial cable / connector and the AT-140 does not sense any RF power, then it immediately terminates the M-802's "Tune" attempt, and shows "THRU" on the display....
Please tell us what type of coaxial cable and connectors you used here, as well as who assembled them, etc...

When you unscrew these cables, the inside of these connections should be clean and shinny....if they are not, they are suspect...

Also, check the coaxial cable with an ohm meter / DMM....
--- Checking the cable's center conductor end-to-end, should show almost zero ohms...
--- Checking the cable's shield end-to-end, should also show almost zero ohms...
--- Checking the cable for "shorts", between the center conductor and the shield, should show almost infinite ohms (more then a few Megohms)...

If you do not get the resistance results listed here, you have a problem!!!
Best thing to do is simply replace the cable / connectors with new / known-good cable/connectors.....but, that is not possible, and these are solder-on connectors, they can be repaired / reassembled, but only by someone trained/experienced!!

BTW, I've seen some VERY poor coaxial cables used, and VERY VERY poor coaxial cable connections done by so-called professionals, especially the boat manufacturers' "professionals" on their assembly line, and "marine electronic technicians" doing commissioning of new boats...
So, be aware that even if you think the factory did all of this, so it's got to be good....it might very well be the problem....
Just wanted you to be fully informed!

So, even if the tuner control wires and connections are good and clean, and the M-802's internal 5amp fuse is good, thereby providing the AT-140 with its "13.6vdc" power (you already verified this above in #3)....
If you have a faulty/defective/shorted/open coaxial cable and/or coaxial cable connectors, it will not tune and it will seem to check okay with a simple DC power check...

SO....
So, my first recommendation (after telling us WHERE you are at, and telling us if you are receiving signals okay) is to check all the wiring to/from the M-802 and AT-140, including the coaxial cable / connectors / line isolator (you do have a coaxial line isolator, don't you?)....




5) You write that you have the same "no tune" problem, but also have no output at all?
Quote:
Originally Posted by Karend007 View Post
I have the same problem (won't tune)...
When I speak or whistle in the mic, I get no signal strength bars on the display, so I am thinking no power from the radio as you say above
Can you clarify if you do in fact have any actual RF power output? (such as in FSK mode, etc.)

A good way to determine if the radio is transmitting a signal, is of course watching the display's power output meter (8 segments), but also by monitoring actual 12vdc current draw...although attempting to do this with just SSB voice or a "whistle" can be difficult / problematic, so for troubleshooting this from afar, it is best to use FSK mode to first test the M-802's power amp....

Here is the first way to do this:
a) First, make sure you've selected "Hi-Power" mode.....which is "F / func" and "9"...("F / func" button is the bottom button of the three immediately to the right of the M802's display...)
And then please select an unused/quiet channel...such a 16mhz or 22mhz marine simplex channel at night, or a 4mhz marine simplex channel during midday....
Preferably a channel that you have NOT previously tried with the M802....

b) Then press the "Tune" button on the M802 control head (top button of the three immediately to the right of the M802's display).....preferably with someone close to the AT 140 tuner, who can listen for some "clicking" sounds inside the tuner...this will take only a few seconds at most, and may take only one second.....
You should see the "Tune" indicator (the very top edge, towards the left-hand side, of the display) flashing while it's tuning, and then "Tune" should stay on steady....
{Although, if you don't have any output and/or if the tuner is faulty, and/or the tuner control cable / connections are faulty, and/or the tuner's "13.6vdc" power is not coming out of the radio (such as when the M-802's internal 5amp fuse is blown), you will of course not see "TUNE" indicated, but rather "THRU"...}


c) Press the "Mode" button (middle button, of the three buttons immediately to the right of the display) on the M802, a few times, until you've selected FSK ("FSK" will be displayed on the top, center, of the M802's display where "USB" was).....

d) Then press the microphone Push-to-Talk button, on the upper-left side of the microphone, while watching the M802's display......
(Hold the microphone Push-to-Talk down for 2 - 3 seconds, while watching the display....and then release...)
In addition to the "TX" (transmit indicator) showing on the immediate left-hand side, middle, of the display, you should have seen the M802's power output display, at the bottom left-hand side, ("S/RF Meter")...and this power output indicator, should show a full-scale reading (all 8 segments, I think), thereby indicating full transmitter output.....

This determines if the M-802's power amp is actually working, even if the microphone element is defective, or if there is a problem with the mic amp circuit, etc. the radio should still transmit an FSK carrier here....
And, even if the tuner is not working, and the radio is presented with a very poor SWR, it will still transmit a signal, albeit a weak signal which would only show one or two segments on the radio's power output display...

If you get NO segments at all to display when in transmit mode, in "hi-pwr", in FSK transmit, then you probably have an internal M-802 power amp (PA) failure (very rare!), but please check the radio's dc current draw just to be sure here....
In transmit mode, with NO signal being transmitted, but with the PA biased on, you should see about 5.5 amps of current draw by the radio...
If you have only 2.5 - 3amps (or less), then the PA is not biased on, and is probably toast (very rare)....
But, if you DO see 5 - 6amps, then the PA is probably okay, and there is another problem we'll need to look for...

If you DO get some segments to show some output (in hi-pwr, FSK transmit), then please tell us how many....
One or two segments, show the M-802 is working properly, but the tuner is not (and the M-802 is transmitting into a high SWR...)

Seven or eight segments (probably not going to happen), means all is well with the PA and the radio is being transmitted into a low SWR....
But, if you still cannot get any output from voice or "whistle", then I'd first suspect the microphone / mic cable / mic plug / etc. (and/or mic amp)...
{but, I doubt that you'll see 7 - 8 segments, as this would indicate that the tuner is working....and if that was the case, you'd have been able to see the "TUNE" indicator and things would be working for you...
But, AFTER you check / clean all connections, you may find this test works....and you've fixed the problem...}



There is a lot more that we can look at, but going further before I have the answers to all the above is getting way ahead of things...
So, please answer #1 and #2, and then if my assumptions of #1 and #2 are correct, please do the tests / check all the cables carefully, and report back....
And, we can move forward at that point...




6) And, finally....please have a look at these videos....
I think you may find them useful...


Icom M-802 Instruction Videos

https://www.youtube.com/playlist?list=PLnN6ygtZ3h2npivDjoFrC-8QKVyMb4tVr

(which currently consists of 18 videos, showing/discussing: basic and advanced Icom M-802 instructions, use, and programming;......along with radiowave propagation and channel/freq choice; atmospheric and man-made noises; radio-telephone calls; Distress Signaling; explanations/demonstrations of HF-DSC calling; etc. etc.)



HF-DSC Communications

https://www.youtube.com/playlist?list=PLnN6ygtZ3h2n3z5nlv-ga2zYuPozhUXZX

(which currently consists of 15 videos showing/demonstrating the features and capabilities of HF-DSC signaling, as well as detailed explanation of what DSC is, how it works, and why/how you should use it...)




I hope this helps....please answer the questions and advise the results of the simple tests above, and we'll get you going!


Fair winds...

John
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