R7000 with Poor Sensitivity

[SCPD]

I just got my IC-R7000 today .. it was an Ebay purchase.

It has poor sensitivity .. barely able to get FM broadcast stations and other signals are weak.

For example .. weather station 162.4000 is S6 on the R7000 and 35 over S9 on my SDR using the same antenna.

Otherwise it seems to be mostly fine.

I am well aware of the 'electrolytic capacitor' issues that may be involved and I have the capacitor kit already, as I was planning on getting all the caps replaced anyways.

It is a great radio .. in spite of its age. The radio is in excellent physical condition and though it cost me a lot to buy it (it will be a $1000 CDN radio all in when I am done), I am still very happy to add it to my shack.

I am interested in hearing from other R7000 owners .. re their experience with low sensitivity issues, or other issues that I should be aware of going forward.

 

[Boatanchor]

The ICR7000 and R7100 use some pretty obscure (epoxy coated 8 or 10pin inline package from memory) hybrid amplifier modules in their IF stages. I would put my money on one of those being faulty.

Or, it could be something simple like a faulty switching relay in the input attenuator circuit.

Or, a number of other things..

 

[Boatanchor]

I would tune to a known strong signal, take the covers off and start gently prodding the RF and IF PCB's and components with a non conductive probe. There is a good chance that there will be a dry joint somewhere and a little mechanical pressure/movement/prod will kick some life back into the old girl. Once you know roughly where to look, take the PCB out and re-solder everything.

Get hold of the service manual (available online) and check the various +&- power supply rails.
The Icom receivers use a DC-DC converter to generate the required positive and negative rails.
It is this DC-DC converter that gets so hot during operation.

 

[SCPD]

I have the service manual .. and one of my friends is going to look at the radio for me soon. I have the capacitor kit .. it is on the list of things to do.

The radio does receive .. I will post what we find out to this thread once I know more.

Also going to get it working on 12v so that it stays cool.

 

[ratboy]

Poking around with a plastic probe is a good idea, just make sure you keep the volume down. If you get lucky and hit the right spot, it might blow your head off.

Some very strange problems with these old timers are simply due to the cap issues, but I've fixed more than a few R71A's and 7000's by going in and tightening the screws that hold the PC boards down. More than a few of these radios never had the screws tightened in the first place, and I've seen some where the PC boards can be wiggled because the screws have backed out from vibration and just never being snugged up in the first place. At about 30 years old, these things sometimes oxidized plugs and other issues. Removing and reseating all the plugs is a good idea too. One thing that surface mount contsruction of newer radios has done is eliminate a lot of potential plug issues, along with a greatly decreased chance of bad solder joints. Unfortunately, the R7000 and R71A and other radios of the same vintage have a lot of potential failure points in them, just from the way they were built. The last R7000 I looked at had multiple issues, and it turned out it was beyond my abilities to fix all of them, and it was sent off to be fixed by a former Icom tech, who had it up and running for more than I would be willing to pay to get it that way, a little over $300 all together. Good Luck

 

[SCPD]

I am not a soldering iron in hand techie guy .. it was hard enough undoing the covers and hooking up the 12v yesterday.

I do want to ask the forum if you guys used the molex in the radio, or used something else for 12v if you went that way ?

I think I will go another route .. unless I can fasten that molex securely and I believe you need the Icom kit for that.

It is sure a lot cooler than AC though.

I leave that part up to my much smarter friends. I can spin the knobs and play with the buttons .. but otherwise I stay away. I would likely break something rather than fix it.

But my radio seems to be out 2.5 kHz on VHF and almost 9 kHz on 800 MHz.

That is a bit of a pain .. but I am sure that it is something that we can fix. The good thing .. these are old school radios, no surface mount anything. That is either good or a curse depending on how you look at it.

But I am still having fun with the radio though .. though it is a bit deaf to anything but strong signals.

 

[dkf435]

I do want to ask the forum if you guys used the molex in the radio, or used something else for 12v if you went that way ?

I think I will go another route .. unless I can fasten that molex securely and I believe you need the Icom kit for that.

It is sure a lot cooler than AC though.

I leave that part up to my much smarter friends. I can spin the knobs and play with the buttons .. but otherwise I stay away. I would likely break something rather than fix it.

But my radio seems to be out 2.5 kHz on VHF and almost 9 kHz on 800 MHz.

Was trying to figure out what you were saying about the rear Molex needing the bracket until looking at the ebay one from October 10 and it has the blank plate, as my R7000 has the power supply plate with the hole in it with the connector mounted.

Using the Molex it will run cooler the wire next to the pointed end is positive with the second wire being the positive from the power supply and is looped with the shorting plug and the fourth wire is the negative.

I have a real unused IC-CK70 kit and all it has is the standoff bracket that the ears of the Molex lock into and the dual fused DC cable. The connectors are available from several sources, the bracket could be made with a drill press and file. If needed may be able to take a picture of the bracket.

Running radio off of a well regulated power supply will help longevity of the radio.

Had one of my R7100As drift some on 800MHz and there was one point to check with freq counter and tweeked a trimmer to bring it back now one of the R8500 needs it also.

David

 

[SCPD]

Was trying to figure out what you were saying about the rear Molex needing the bracket until looking at the ebay one from October 10 and it has the blank plate, as my R7000 has the power supply plate with the hole in it with the connector mounted.

Using the Molex it will run cooler the wire next to the pointed end is positive with the second wire being the positive from the power supply and is looped with the shorting plug and the fourth wire is the negative.

I have a real unused IC-CK70 kit and all it has is the standoff bracket that the ears of the Molex lock into and the dual fused DC cable. The connectors are available from several sources, the bracket could be made with a drill press and file. If needed may be able to take a picture of the bracket.

Running radio off of a well regulated power supply will help longevity of the radio.

Had one of my R7100As drift some on 800MHz and there was one point to check with freq counter and tweeked a trimmer to bring it back now one of the R8500 needs it also.

David

Thanks .. I am running it from 12v presently and it is much much cooler.

I am going to talk to one of my friends about what type of connector we can use to route the power from the inside to the outside.

I do not really care what we use, as long as it works and is a secure connection. Likely I will reseal the hole for the molex and we will use some other type of connector.

I am going to keep checking Ebay for that kit, but likely we will find a solution once he looks at it.

Eventually the capacitor kit will be installed and I will see how the radio works then .. to see if any other tweaking will be needed. But I will deal with that when the time comes.

 

[dkf435]

There was a CK70 listed on Ebay several weeks back but it did not have the standoff bracket. Using the Molex with the jumper allows you to switch from the internal supply to external quickly. I have a Philmore # 247 dc coaxial jack mounted on the back of the R71A to power preamps but you probably could use it for the power supply.

David

 

[SCPD]

There was a CK70 listed on Ebay several weeks back but it did not have the standoff bracket. Using the Molex with the jumper allows you to switch from the internal supply to external quickly. I have a Philmore # 247 dc coaxial jack mounted on the back of the R71A to power preamps but you probably could use it for the power supply.

David

I will never use the AC with this radio. So .. only looking for 12v connection. I am leaning towards binding posts right now but I shall see what is easily available.

 

[dkf435]

I would say try to find a chassis mount coaxial jack the same size as what the R75 and R8500 use it is the same as some of the portable tvs used. Bypassing the molex connector and Icom power cord removes the DC supply fuse.

David

 

[SCPD]

I would say try to find a chassis mount coaxial jack the same size as what the R75 and R8500 use it is the same as some of the portable tvs used. Bypassing the molex connector and Icom power cord removes the DC supply fuse.

David

My DC cable is fused. It will really be what is available and what we can easily solder. I don't like coaxial connections, as they unplug too easily, so that is probably my last choice. The cord is also plenty long.

But really the radio is working right now and is cool so .. when the time comes to replace the caps this will likely be done at the same time.

 

[SCPD]

Here is an update to my post re the R7000 sensitivity ..

We actually measured the radio .. and other than some issues on 700+ MHz as noted below, it performed well.

Frequency / Measured Sensitivity (minimum squelch activation in uV)
All FM except 127.5 MHz which was AM.

98.0 MHz 0.16 uV
127.5 MHz 0.04 uV
147.0 MHz 0.17 uV
155.0 MHz 0.14 uV
420.0 MHz 0.08 uV
447.0 MHz 0.11 uV
772.0 MHz 0.11 uV
868.0 MHz 0.11 uV

So my R7000 has a small issue on 700+ MHz but I think we will get to that in due time. (it is off frequency by up to about 9 kHz .. and you have to use the center feature above 700 MHz) Below 700 MHz .. the indicated frequency was correct.

I can confirm that the R7000 is the most sensitive air band radio that I have in listening tests. The above confirms my findings.

 

[SCPD]

Just a note .. we pulled out the signal generator and the service manual today and adjusted my R7000. It is now within spec for all frequencies. It was fun .. and so rewarding to get it all fixed up.

These are great radios.