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R.I.P. Icom R75?

GB46

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I would expect that resetting the microprocessor would also clear the user settings, but they're just as I left them, and when the radio came back on, it was still tuned to the station I had been monitoring last. Also, why would a CPU reset also prevent the power from being turned on altogether, and for such a long time? When my computer crashes, the power stays on, and all that's needed to get it back into action is a simple reboot . My ATS-909X, on the other hand, has crashed occasionally and shut itself off, but hitting the power button turned it right back on; only the clock needed to be reset. But then, I don't understand digital electronics, anyway; I just use these devices and hope for the best.. :)
 

GB46

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Bummer. I got 1 I am selling. Too many HF radios at my QTH. Be too expensive sending it to Canada though
Funny you should mention that. While mine was still not working, I received a suggestion that I consider selling mine for parts, but the cost of shipping it (and the accompanying power supply) would have been way too expensive for sending it stateside.

I wouldn't mind replacing the Hammarlund SP-600 that I foolishly sold back in the 1970s, but can you imagine how much it would cost to send that 65-lb. boat anchor to me? There are no radio equipment stores where I live; the closest would probably be in Vancouver, which is where I bought my previous SP-600 second-hand. And it's difficult to imagine another one in as good a condition as mine was. Everything worked perfectly, and even the front panel had been beautifully repainted.
 

ridgescan

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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:
Just like an old watch stuffed in a drawer LOL You pull it out 20 years later and it works fine unlike it did when you stuffed it in there.
 

GB46

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Just like an old watch stuffed in a drawer LOL You pull it out 20 years later and it works fine unlike it did when you stuffed it in there.
Exactly. I have a few old watches archived like that. The cheapest among them, a couple of Timex digitals with broken plastic bands, keep on working. One of them is 9 years old and still running on its original battery. There's only one expensive watch in that drawer. It runs on a tiny internal generator kept in motion by arm movement, and stores its power in a capacitor, which no longer holds a charge. To have the capacitor replaced would cost me an arm and a leg. I'd rather just keep the arm and leg.
 

Boombox

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I would expect that resetting the microprocessor would also clear the user settings, but they're just as I left them, and when the radio came back on, it was still tuned to the station I had been monitoring last. Also, why would a CPU reset also prevent the power from being turned on altogether, and for such a long time? When my computer crashes, the power stays on, and all that's needed to get it back into action is a simple reboot . My ATS-909X, on the other hand, has crashed occasionally and shut itself off, but hitting the power button turned it right back on; only the clock needed to be reset. But then, I don't understand digital electronics, anyway; I just use these devices and hope for the best.. :)
Because the microprocessor controls the power going to the radio? In most modern radios, power on/off is a microprocessor / firmware function, not a physical power switch. Perhaps the R-75 has a physical power switch -- from the brochure, it doesn't look like it does.

I have a Sangean that sometimes has a flakey power switch. If the radio has seen power for a month or more sometimes the power button needs to be pressed more than once to operate. There is nothing wrong with the switch or the radio -- it's a microprocessor glitch. Probably not scanning the buttons correctly if it's powered up too long (months at a time). I have heard of this happening with other portable radios (a guy said his CCrane had glitches like this).

This all, of course, depends on how the radio is designed, and I don't know how an Icom R75 is programmed or wired.
 

GB46

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Because the microprocessor controls the power going to the radio? In most modern radios, power on/off is a microprocessor / firmware function, not a physical power switch. Perhaps the R-75 has a physical power switch -- from the brochure, it doesn't look like it does.
I have the service manual, but can't make head or tail out of the schematic, esp. because it's divided into sections for several different circuit boards.

Anyway, with the radio off and unpowered, when I connect a power supply and switch the supply on I can hear the click of a relay inside the radio, even before I press the power button. So yes, the power must be switched by the processor, and you have to hold the power button for a second to shut it back off. A computer works the same way, except that you normally shut it down through the software, and only use the power button if the computer locks up so badly that you can't shut it down any other way.

When my R75 wasn't responding, however, connecting the supply didn't cause the click of a relay. I guess the CPU was actually live, but too screwed up to handle the power-on function. My partner suggested that maybe something in the radio was holding a charge, and that's why it took so long for the radio to come back to life.
 

GB46

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I got rid of my stock power supply and bought a reg power supply......heard of too many problems
Same here; I replaced mine with a regulated linear supply, rated at 4 amps. Those switching AC adapters usually produce plenty of RFI, so it was surprising that ICOM included one with the radio. The only adapter I have that doesn't produce RFI is the adapter provided by Sangean with my portable, It outputs 9 volts AC, with the DC conversion and voltage regulation done inside the radio itself.
 

Boombox

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I have the service manual, but can't make head or tail out of the schematic, esp. because it's divided into sections for several different circuit boards.

Anyway, with the radio off and unpowered, when I connect a power supply and switch the supply on I can hear the click of a relay inside the radio, even before I press the power button. So yes, the power must be switched by the processor, and you have to hold the power button for a second to shut it back off. A computer works the same way, except that you normally shut it down through the software, and only use the power button if the computer locks up so badly that you can't shut it down any other way.

When my R75 wasn't responding, however, connecting the supply didn't cause the click of a relay. I guess the CPU was actually live, but too screwed up to handle the power-on function. My partner suggested that maybe something in the radio was holding a charge, and that's why it took so long for the radio to come back to life.
I don't have a radio as complex as an R75, but my Sangean PR-D5, the radio with the power button issue, shows the matrix of buttons fairly clearly on the schematic, as well as the traces to the microprocessor. That's how I figured out most of what I was dealing with was a firmware glitch, although the button itself is touchy and not 100% positive like the other buttons.

Either way, glad things worked out. It's a drag when a trusted radio is no longer so trusty...
 

GB46

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I don't have a radio as complex as an R75, but my Sangean PR-D5, the radio with the power button issue, shows the matrix of buttons fairly clearly on the schematic, as well as the traces to the microprocessor. That's how I figured out most of what I was dealing with was a firmware glitch, although the button itself is touchy and not 100% positive like the other buttons.

Either way, glad things worked out. It's a drag when a trusted radio is no longer so trusty...
Yeah, it was something I used to swear by, until I found myself swearing AT it, but now it's working flawlessly again (much like what happened with the ATS-909X).

That PDF of the R75's schematics gives me a headache. They're obviously meant to be printed on very large sheets of paper and hung on a wall over the test bench. When I'm looking for a specific part of a circuit, it turns out that it's way off the screen, so I have to scroll sideways to hunt for it. In the case of the R75 there are buttons in the PDF labeled "Complete View" or "Right Side", but in trying to follow the tracks of the component, I lose its scent, so to speak.

The Sangean's schematic is easier to navigate, but gives no hint what kind of part I'm looking at, just its part number. A diode simply marked D9, for example, doesn't tell me much about the kind of diode or its function in the circuit. Checking it against the parts list isn't very informative, either.
 

GB46

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Well, the ongoing saga of my R75 continues: At random times during a listening session, the radio suddenly starts turning itself off and on very rapidly in an endless loop. This will happen even if I haven't touched any of the controls and am just sitting and listening. The radio acts like it's having an epileptic fit; it's just too weird! There's no stopping it with the power switch, so I have to shut the power supply off, instead. If I leave it off for a few minutes, the radio recovers when I apply power again. This may or may not be related to the earlier problem of not being able to turn it on at all.
 

Boombox

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Sounds like it's not the switch itself, being that pressing the power switch does not change things. It's firmware, or some other issue that would be far beyond my pay grade to suggest...

Hope you're able to get it fixed. That sounds like a real bummer.
 

GB46

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Sometimes I think that even the technicians don't understand what causes some of these malfunctions. I'm no one to second guess the problem, either, but it has occurred to me that maybe a faulty component in the control circuitry starts overheating, causing either a short or an open contact. It then quickly cools down enough to close the contact again, and the whole process repeats itself in an endless loop. Trouble is, it starts at random times, so I never know when to expect it. It could start after the radio has been on for several hours, or even just a few minutes. Just when I think everything's fine, I 'll be away from the receiver while eating my lunch, and happen to notice out of the corner of my eye that the thing has gone bonkers again.

I've gone back to using my portable, on which I hear everything I could hear on the ICOM, anyway. Of course, I miss the ICOM's ability to filter out some of the noise, and its better selectivity and tuning accuracy. What I don't miss is its poor audio quality. Sure, the voices come through very clearly, but the overall sound of them grates on my ears.
 

Boombox

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Could it be the power supply itself? Is there a way to swap power supplies? Or the power supply connector being somehow affected by heat?
 

GB46

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It's the only power supply I have, but I doubt if that 's the culprit. All the connections look solid, and nothing is getting hot. Yesterday I had intended to measure how much current the receiver was drawing from the supply during one of those episodes, but oddly enough there were none of them for the entire day. It seems more like some kind of random computer glitch, like the one I get with my laptop occasionally. At roughly one month intervals the computer will crash when I go to switch on the wifi. The blue screen comes up, full of some text in tiny white letters that are distorted and impossible to read. A few seconds later the computer reboots itself and everything's back to normal.

This receiver is more like a computer with a built-in radio, rather than a radio with a built-in computer. It has a mind of its own. If I had a mind like that I'd be in big trouble. :)
 

majoco

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I do vaguely recall from another forum that the physical on/off pushbutton switch has been known to be faulty.
 

GB46

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I do vaguely recall from another forum that the physical on/off pushbutton switch has been known to be faulty.
Well, when the receiver is not throwing a fit, or has recovered from one, I can toggle it off and on by the power switch dozens of times without any problems. I doubt if I could do that if the switch were faulty. Also, the problem often shows up without touching anything on the radio or causing any vibrations in its vicinity. No movement of the switch will bring it back to its senses at that point, either, so I always have to kill the power supply. If I turn the supply back on after a short while, the receiver comes on without having to use the switch, unless I wait a very long time before restoring power.

At any rate, a day after my previous post, in which I mentioned that the radio had gone a whole day without acting up, it started up again. I was sitting with my back to the radio, which was on, but I wasn't listening at the time. I started to hear a chattering sound, so I suspected it was that relay in the radio, but when I went to look at it there was nothing wrong. I ignored it for quite some time, then went back to it, only to discover that it was caught in one of those endless loops again, and I hadn't heard the relay that time. I eventually lost patience with the thing, and it's back in storage again.
 

Boombox

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I'd try a different power supply, even a battery (if it takes 12 volts), just to see if that is the problem.
 

kruser

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I'd try a different power supply, even a battery (if it takes 12 volts), just to see if that is the problem.
Yep, a bad capacitor in the OEM supply will cause the exact issue the OP is seeing.
And things do NOT need to get hot when a capacitor has failed so physically feeling for excessive heat is not a good test.

The OP does say he is using a linear supply so a bad cap would not usually cause a problem as they often do with switcher supplies.
I'm still thinking a bad cap though but somewhere in the radio between the power jack and the processor and related power switching circuits.
 
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