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R.I.P. Icom R75?

Joined
Feb 4, 2017
Messages
304
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British Columbia, Canada
#23
Don't know if anyone already said this but the board mount solder joints for the DC power jack tends to become loose. Try wiggling the line jack (gently) while attempting to engage the power button and see if it catches. I myself have this trouble and have something wedged between the jack board mount and something behind it. Works fine now.
That didn't work, either. Some other part must be faulty, or maybe the power supply, which is only two years old.
 
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#24
You may just be looking at a tired old supply that wants to live, but other than being able to burn out a 3v bulb, when real work is being asked of it, it crashes the voltage. Grab a multimeter and see. The good news is that you can adapt the original cable to a new supply.

This is not uncommon for power supplies which spend most of their life being "ON" 24/7 for most of their lives to finally just crap out suddenly when power cycled from a move, etc.
Well, this is actually my second power supply, which I bought only two years ago when the first one died. It hasn't been used more than a year all told, because I had stored it away along with the R75 when finding the portable sufficient for my needs, more compact and a lot less noisy. I had only put the R75 back in action a few days ago out of curiosity.

BTW, this supply isn't a wall wart. It's a regulated linear supply rated at 4 amps. The previous one was somewhat similar, but without proper overload protection; it didn't even have an accessible fuse, for that matter. As for the adapter that came with the receiver, I ditched that years ago, because it was the switching type and caused far too much RFI.

My next shopping trip will include a multimeter; if the power supply is OK, a multimeter could still prove handy for other jobs.
 
Joined
Sep 8, 2006
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3,046
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Stockholm, Sweden
#25
Remember that power supplys need to be measured under load. I usually do that by inserting a tiny wire in the connectors plus polarity to the device it is powering and then plug in the power supply connector so that I can measure the voltage to the chassi while I power on the device.

/Ubbe
 
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#27
Yes, I intend to check the supply under load tomorrow once I've picked up a multitester. No shopping trips today, however, as driving conditions are currently treacherous due to a heavy snowfall overnight. If the power supply is good I'll then e-mail Icom.

Thanks, everyone, for all your helpful replies. I'll return with an update once I find out where the trouble lies.
 
Joined
Feb 4, 2017
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#29
A downed radio sucks bigtime, I know it personally. I hope you find 'er fixed soon.
Thanks, ridgescan. Meanwhile, my portable is bringing in just as much on the HF bands -- make that "as much of practically nothing", considering current conditions and my location.

At any rate, a downed radio is not the end of the world for me, radio being only one of my two hobbies. I'm not quite as obsessed with radio as I was during my youth.
 
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#30
Update: I've acquired a good multimeter, and here's what I've learned so far:

1) Continuity of the power cable and plug is fine (0 ohms resistance). Same goes for both the supply fuse and the radio's internal circuitry fuse.

2) The power supply checks out OK. With no load, it puts out 13.9 volts. When connected via the power cable to the receiver, the result is again 13.9 volts. Pushing the power button doesn't change anything, there's not the slightest fluctuation in the voltage.

3) The same voltage appears at the radio's circuitry fuse holder, showing that the DC input jack is OK, as well. The voltage is ideal, since ICOM specifies a voltage requirement of 13.8 volts +/- 15%, which allows for voltages between about 11.75 and 16.

4) The current drawn from the power supply by the radio is a feeble .015 amps, even when pressing the power button. The power supply is rated at 4 amps, and since the receiver's rating is 0.9 amps when on standby, and 1.1 amps at maximum audio, the rig is obviously not drawing power.

There must be an open circuit or a burned out component somewhere in the radio's circuitry. I wonder if a static charge managed to cause that without blowing the fuse. I always ground myself before working on this stuff, especially because the air is very dry here in the winter. Besides, the radio failed before I had even opened the cabinet.

My next step will be contacting ICOM to see if they have any suggestions other than shipping the radio to them for repairs.
 
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#31
I just heard back from ICOM Canada's service manager. He says I've checked most of the logical things that needed to be checked, and that the radio would have to be put on their bench for diagnostics, which would cost me $50. After diagnostics I'd be given a repair estimate, and if I approve, the diagnostics charge would be put towards the final bill ( (which of course is in addition to shipping charges both ways).

Well, considering how little I've used the radio since I got my portable, not to mention the poor HF propagation, I don't think I'll bother. I'll put it on the shelf with my scanner, the one with the non-functioning LCD. Maybe someday I can start a museum of inoperative electronic equipment. I also have a big, heavy music keyboard that has developed an LCD problem. It weighs 35 lbs. (too awkward to ship) and is even older than the R75, so it can go into the museum, too. Hopefully my Sangean portable radio won't end up there in a few years. :D
 
Joined
Dec 25, 2008
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#32
It's a hideous schematic diagram but going by what has been said so far I would be suspecting the pushbutton on/off or the power relay that you say doesn't click anymore. Now that you have a multimeter you should be able to trace where the 12volts goes and where it stops going - if you see what I mean.
 
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#33
It's a hideous schematic diagram but going by what has been said so far I would be suspecting the pushbutton on/off or the power relay that you say doesn't click anymore. Now that you have a multimeter you should be able to trace where the 12volts goes and where it stops going - if you see what I mean.
Martin, the relay normally clicks as soon as a live power supply is connected to the radio. This is before the push button is pressed to turn on the radio. That's the click I no longer hear. So if the power button were faulty, I'd still be able to hear the relay. I searched the entire service manual for relays, and could identify only three. They are for the standby, antenna switching and attenuator functions. None of them seem to be directly in line with the power switch.

At any rate, I can't trace the incoming power any further than the internal circuit fuse without exposing the bottom of the main board. This would entail lifting the board off the chassis. Just removing the six screws isn't enough, as the main board has five different ribbons and several jumper cables that are connected to the other boards, for example the PLL board, logic board, display board, etc. The PLL board is on top next to the main board, but the other boards are hidden below those two. I also noticed a few components on the main board that are inside some kind of retaining clamps at the side of the cabinet.

The whole thing makes my head spin, and even if I could get all that stuff apart, I'd never be able to reassemble it later on. Getting replacement parts, if needed, would be another challenge, not to mention my poor soldering skills. It's just not worth the effort, especially considering that I've never heard anything on the R75 that I couldn't pick up just as easily on the portable -- when there was anything to pick up, that is. Today's reception has been terrible here. About all I can get is FT8 on the ham bands and Radio Havana Cuba.
 
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Joined
May 28, 2009
Messages
2,604
#34
Sorry to hear that, but don't give up just yet!

That 15ma of current being drawn shows that it isn't totally smoked, but just in "standby" awaiting a power switch push which never comes.

Instead of mothballing it, it is possible that the power switch is stuck after you turned it off. Can you message the switch at a strange angle to unstick it? Or worst case, cut the covering off and see if you can manipulate it that way ...

Thermal *gentle* shock - put it in a plastic bag (squeeze as much air out as you can), and leave it in the refrigerator for an hour or two. Then remove it, but DONT remove it from the bag for another hour as it warms up. (so as not to create excessive moisture).

Or maybe hit the power switch with freeze spray for a little bit. No freeze spray but have some dust-off air can - hold can upside down and squirt switch a little.

Perhaps the rapid thermal change can help unstick the switch (if that's the problem).

I suppose worst case you could part it out, like if you have any optional filters installed, or offer it up as a "parts only" radio.
 
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#35
Sorry to hear that, but don't give up just yet!

That 15ma of current being drawn shows that it isn't totally smoked, but just in "standby" awaiting a power switch push which never comes.
If that's the case, the relay should be clicking in even without pushing the power switch. This is the way it has always worked. Starting from when the radio was connected to the power supply and the power supply was not yet turned on: As soon as the power supply was turned on, the click was heard. The radio would still be off at that point, and standing by for the power switch to be pressed.

I'll try and see if the power switch is stuck. I have some spray on hand. As for your gentle shock method, that plastic bag could prove handy if it doesn't work, i.e. "bag it and tag it", if you know what I mean. :lol:

I suppose worst case you could part it out, like if you have any optional filters installed, or offer it up as a "parts only" radio.
There are no optional filters installed, but it does have the DSP unit, which I had to install as an option, only to find out later that the radio had started to be offered with the unit included.

Thanks for the suggestions!
 

bob550

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#36
Sorry, but have you verified that the electrical outlet you are using is working and providing the proper voltage? Try plugging another appliance into the same outlet, or try your R75 on a different house circuit.
 
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#37
Sorry, but have you verified that the electrical outlet you are using is working and providing the proper voltage? Try plugging another appliance into the same outlet, or try your R75 on a different house circuit.
The electrical circuit I was using during the test was the same one that is currently successfully powering this computer, as well as the adapter for my portable radio. There's 120 volts at every outlet in this apartment except for the 240 volts for the kitchen stove. Also, the power supply could hardly have produced its rated voltage if there were something wrong on that circuit.

@hertzian: The power switch remedy didn't work and the switch doesn't appear to be faulty, unless, of course, it has become disconnected from the board behind it. I'm now going to stop trying to revive the R75 and just use the portable.
 
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GB46

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Feb 4, 2017
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#39
Well, now I'm really baffled! Since my last post on this thread, I had stored the R75 away without connecting it to the power supply for more than 4 months, but today I had a hunch, powered it up, and it came back to life, with all the memory channels intact. I hadn't done anything more to it; the thing simply decided to start working again! If I had sent it in to ICOM, it probably would have started working as soon as they put it on the bench for diagnostics, and of course I'd have had to pay for that, plus shipping in both directions.

Maybe the receiver decided it had needed a rest. :confused:
 
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