Icom The final solution to my R75 problem

[GB46]

I finally got my R75 to stop misbehaving and going off and on at random but frequent intervals. It was so easy to fix: I simply threatened the radio with the dumpster.

Not really ... just kidding. What actually happened was this: Yesterday morning the R75 started acting up again, and finally quit altogether. I couldn't power it back on, and suspected that whatever component was starting to fail had finally died altogether.

It then occurred to me that it might have blown the internal fuse in the process, so I took the lid off and examined the fuse. It looked OK, but I decided to pull it and run a continuity test on it. Well, it was too easy to pull out of the holder, and I noticed that one end of the fuse wasn't sitting securely in its spring clip, but was instead resting on top of it. This was likely overlooked for a very long time, and causing intermittent contacts to the power supply. Once I pushed the fuse back in and made sure it was good and tight, the radio sprang back into service and hasn't failed at all since then.

So the cause of the problem was way simpler than all those theories that we explored over the past year or so. Kind of embarrassing, actually.

 

[Boombox]

Glad you found out what the issue was.

A lot of times what we think are mysterious issues thankfully have simple fixes. After years of use, my DX-398 would turn itself off periodically, for no apparent reason. Even on fresh batteries. I finally found out it was the spring connector in the battery compartment had made the solder joint holding it to the PCB intermittent. Adding some solder and ensuring that it was well connected to the PCB solved the issue. My DX-394 started tuning in one direction only, which almost looks like it could be a firmware issue. The encoder needed a shot of spray to clear some oxidation. I got lucky in both cases. But I'm glad of it...

So yeah, it's cool you found out what the issue was. It will probably help someone down the line, who might have the same exact issue.

 

[GB46]

Glad you found out what the issue was.

A lot of times what we think are mysterious issues thankfully have simple fixes. After years of use, my DX-398 would turn itself off periodically, for no apparent reason. Even on fresh batteries. I finally found out it was the spring connector in the battery compartment had made the solder joint holding it to the PCB intermittent. Adding some solder and ensuring that it was well connected to the PCB solved the issue. My DX-394 started tuning in one direction only, which almost looks like it could be a firmware issue. The encoder needed a shot of spray to clear some oxidation. I got lucky in both cases. But I'm glad of it...

So yeah, it's cool you found out what the issue was. It will probably help someone down the line, who might have the same exact issue.

I used to have a Sony 2010 that would abruptly lose power if I moved the radio around a lot. It would also lose all the memories I had entered. This, too, was a battery connection issue, but not from a bad solder joint. The batteries were quite heavy -- D cells, if I remember correctly -- and simply moved around too much in the compartment. Tighting the springs didn't help, so I had to stuff a piece of cotton between the lid and the batteries to hold them steady. That solved the problem, until I replaced the radio with the R75. The 2010 had suddenly lost sensitivity, probably due to a static charge on the whip antenna, which is well-known to damage a transistor in the front end.

As for your DX-394, was it made by Sangean? I had the same problem with the decoder in my AT-909X soon after I bought it, but I solved it the way you did. I'd prefer that the decoder were optoelectronic instead of similar to a potentiometer. The decoder in the R75 has never given me a moment of trouble since I bought it more than 20 years ago.

 

[Boombox]

Re: the DX-394, no, it wasn't made by Sangean. It actually was custom designed for Radio Shack, and made for them only. A lot of guys in the UK really got into them, being that the DX-394 was ubiquitous and apparently easy enough to modify.

 

[GB46]

I've only owned two Radio Shack SW receivers, the Astronaut 8 and the DX-300. Both of them were disasters.

Regarding the fuse holder mentioned earlier, I had a very similar experience with a rusty old Volkswagen Beetle I had bought very cheaply back in 1969. I had to have the engine completely overhauled. When I left the repair shop the car was running like a brand new one. A few miles down the road I parked it to take a walk around the area, and when I got back to the car it wouldn't start. It wouldn't even turn over, and some warning lights came on. So I phoned the mechanic, who came racing out there to meet me. He ducked under the dashboard, wiggled one of the fuses, and the car came back to life.

 

[mbott]

I'm picking up a second R75 tomorrow. Don't really need it as the one I already have has the sync detector (modified by Kiwa) and the DSP. I expect I'll make sure it functions well and put it on the market. Will also pick up a DX 160 and that will get a little play time before I decide its fate.

--
Mike

 

[Boombox]

^^^^^ FYI.... the DX-160 is an excellent MW DX receiver. OK for listening to SW, and HF hams (Bandspread + BFO control combined in a certain way acts as a passband control) but it shines on MW. Easy on batteries if you wire up a DC supply.

As for the performance of the DX-394, it worked well for me, as I'm in a low signals area. Only time I experienced overload was during HF Ham contests and the master blasters with their linears were splattering the band, intent on raising that DX... At those times, I'd get a little crosstalk. Still, it wasn't a huge problem for me.

 

[KC5AKB]

Simple fix / But the one that’s gets over looked sometimes when troubleshooting.
Glad you are back up and listening.

 

[GB46]

Only time I experienced overload was during HF Ham contests and the master blasters with their linears were splattering the band, intent on raising that DX... At those times, I'd get a little crosstalk. Still, it wasn't a huge problem for me.

I get a lot of splatter from a ham who lives halfway down the block from me. He also yells into his microphone, which makes his voice peaks much higher. I usually know when he's going to be on the air, because he checks into various ham nets as soon as they open, two on 40 and one on 80 meters. Recently his splatter showed up way out of the band, on top of one of the 11 mHz frequencies where those Cuban spy numbers usually show up. I've tried everything to keep him from overloading the R75, including using the 20 dB attenuator and setting the RF gain to minimum, but no luck. And yet my antenna consists of only 23 ft. of wire inside my apartment. I'd probably hear him with no antenna at all. Maybe his signal has been getting onto the power lines.

The guy is operating from an apartment building and always checks into the nets as a QRP (low power) station. In fact, he once said he was running only 5 watts. Fortunately, he only just checks in quickly and then leaves the net, unless he can't reach anyone and keeps yelling for a relay. It would be a lot worse if he were a rag chewer.

 

[n5rv]

I enjoy my R75. I recently acquired an IC-R8600 and even this new radio hasn't convinced me to get rid of my R75. I enjoy it most for SWB listening.

Very glad you found the issue and putting it back into service!

 

[GB46]

I enjoy my R75. I recently acquired an IC-R8600 and even this new radio hasn't convinced me to get rid of my R75. I enjoy it most for SWB listening.

Very glad you found the issue and putting it back into service!

I can't hear very many SWBC stations at my location, but when they do come in I usually listen to them on my Sangean ATS-909X, because i prefer its audio in AM mode. The R75 serves me better for listening to SSB and decoding digital signals, because its tuning is far more precise than that of the portable. It also has better IF filters, and I find the twin PBT especially useful.

That said, the RFI here is more noticeable on the R75. The noise floor is just as high on the portable, but the R75's audio seems to accentuate the noise. I can switch on the noise reduction, but have to keep its level kind of low -- no higher than 3 -- otherwise it distorts the audio.

Anyway, it looks like the radio won't give me any trouble from now on, knock on plastic -- well, not too much is made of wood nowadays.

 

[n5rv]

I can't hear very many SWBC stations at my location, but when they do come in I usually listen to them on my Sangean ATS-909X, because i prefer its audio in AM mode. The R75 serves me better for listening to SSB and decoding digital signals, because its tuning is far more precise than that of the portable. It also has better IF filters, and I find the twin PBT especially useful.

That said, the RFI here is more noticeable on the R75. The noise floor is just as high on the portable, but the R75's audio seems to accentuate the noise. I can switch on the noise reduction, but have to keep its level kind of low -- no higher than 3 -- otherwise it distorts the audio.

Anyway, it looks like the radio won't give me any trouble from now on, knock on plastic -- well, not too much is made of wood nowadays.

If you are running a coax fed antenna on the R75, you might look at using one of the Palomar Engineers noise filters. They are made to keep the noise from conducting down the shield of the coax. In short it's a 1:1 current balun. Using them has reduced my noise quite a bit. Most HF noise level is around S1 and lower on "quiet" solar days. Unfortunately they don't do anything for static crashes.. :/

 

[GB46]

If you are running a coax fed antenna on the R75, you might look at using one of the Palomar Engineers noise filters. They are made to keep the noise from conducting down the shield of the coax. In short it's a 1:1 current balun. Using them has reduced my noise quite a bit. Most HF noise level is around S1 and lower on "quiet" solar days. Unfortunately they don't do anything for static crashes.. :/

Most of those static crashes are inaudible when I use the noise blanker. I can still see them on the S meter, but they can't be heard, and don't interfere with the signal. Those crashes are pretty frequent here, and likely caused by lightning from all the wildfires in our province. The other kind of static crash comes from our electric range if a burner is set to low, which makes it come on and off intermittently by design.

The noise blanker is best, of course, on pulse noise, and completely filters out the noise from vacuum cleaners. Without the NB a vacuum cleaner can completely override everything on the band. The portable has no noise blanker, or noise filtering of any kind. That's when all that stuff can make listening virtually impossible, especially in AM mode.

No, I'm not using coax. There's just the single 23-ft. length of wire going straight to the antenna terminal. Grounding is also impossible in this apartment. The radios are much too far from cold water pipes, and I can't drop a ground wire down from here, as I'm on the third floor. It would be too long for a ground, and not permitted, anyway.

I'd do things differently if I could have a proper outdoor antenna, but that's out of the question.

I seem to get more RFI during the morning hours than during the afternoon or evening. The radio also seems to create some of its own noise from the circuitry, but that happens with most modern radios. The old tube-type boat anchors were much quieter (and much, much heavier).

 

[ridgescan]

Most of those static crashes are inaudible when I use the noise blanker. I can still see them on the S meter, but they can't be heard, and don't interfere with the signal. Those crashes are pretty frequent here, and likely caused by lightning from all the wildfires in our province. The other kind of static crash comes from our electric range if a burner is set to low, which makes it come on and off intermittently by design.

The noise blanker is best, of course, on pulse noise, and completely filters out the noise from vacuum cleaners. Without the NB a vacuum cleaner can completely override everything on the band. The portable has no noise blanker, or noise filtering of any kind. That's when all that stuff can make listening virtually impossible, especially in AM mode.

No, I'm not using coax. There's just the single 23-ft. length of wire going straight to the antenna terminal. Grounding is also impossible in this apartment. The radios are much too far from cold water pipes, and I can't drop a ground wire down from here, as I'm on the third floor. It would be too long for a ground, and not permitted, anyway.

I'd do things differently if I could have a proper outdoor antenna, but that's out of the question.

I seem to get more RFI during the morning hours than during the afternoon or evening. The radio also seems to create some of its own noise from the circuitry, but that happens with most modern radios. The old tube-type boat anchors were much quieter (and much, much heavier).

I'm on the third floor too here and I run two ground wires (of RG8U coax) from my R75 in my living room to the cold water tap under the kitchen sink, and from my R8600 in the bedroom to the cold water tap at the toilet in the bathroom. I use RG8U coax because of the thick center lead (it's almost like #10AWG) as the conduit to these ground points. I ground the RG8U braids at the ground points too.
The final matter is to run these ground leads along the walls and under rugs for aesthetics.
Just saying, it can be done.

 

[GB46]

I'm on the third floor too here and I run two ground wires (of RG8U coax) from my R75 in my living room to the cold water tap under the kitchen sink, and from my R8600 in the bedroom to the cold water tap at the toilet in the bathroom. I use RG8U coax because of the thick center lead (it's almost like #10AWG) as the conduit to these ground points. I ground the RG8U braids at the ground points too.
The final matter is to run these ground leads along the walls and under rugs for aesthetics.
Just saying, it can be done.

It would be pretty tricky here. For one thing, there's wall-to-wall carpeting, which is securely anchored down under the baseboards, ruling out running any cables under it. My wire antenna is suspended from a curtain rod, at about a 45-degree angle from the floor. I tried to tuck part of it under the baseboard to anchor it, but couldn't get it in far enough, even though the wire is very thin.

That RG8U is what I used when I was a ham as a teenager. It had very thick foam insulation around the center conductor, and the outer insulation was really tough. Stripping it for attaching a PL-259 plug was very difficult. We had a TV repairman mount my 11-element 2-meter beam on a ten foot mast anchored to a gable end on the second floor of the house. To get it into my bedroom, where I had my station, he had to drill through the brick wall beneath the window sill using a masonry bit, then caulk around the opening. Seemed like overkill, considering I was only running 18 watts input and probably getting no more than 10 watts to the antenna.

The carpeting here stops at the kitchen, so it would be next to impossible to hide the part of the cable going to the cold water pipe. As for the bathroom plumbing, this is a large two-bedroom suite, and the bathroom is way down the hall from the living room, where my radios are.

If propagation were better and the signals stronger, the noise wouldn't be as much of a problem. The occasional strong signal silences the noise pretty well. I'm just going to tough it out until there's a long-awaited upswing in propagation.