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R.I.P. Icom R75?

GB46

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Joined
Feb 4, 2017
Messages
295
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British Columbia, Canada
#41
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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Joined
Feb 4, 2017
Messages
295
Location
British Columbia, Canada
#43
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.
 
Joined
Apr 1, 2008
Messages
4,472
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San Francisco, Ca.
#44
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

Member
Joined
Feb 4, 2017
Messages
295
Location
British Columbia, Canada
#45
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.
 
Joined
Sep 2, 2012
Messages
808
#46
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.
 
Joined
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Messages
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British Columbia, Canada
#47
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.
 
Joined
Feb 4, 2017
Messages
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British Columbia, Canada
#49
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.
 
Joined
Sep 2, 2012
Messages
808
#50
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...
 
Joined
Feb 4, 2017
Messages
295
Location
British Columbia, Canada
#51
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.
 
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