R7100 Refurbishing the Icom IC-R7100 _ CIV software

chris451rr

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Aug 1, 2008
Messages
78
Location
iowa
I have 3 of the IC-R7100 receivers. I noticed on all of them at different times,
the frequency drifts and is off frequency. Also sensitivity is down.
And you can 're-align' all the oscillators and still have this problem. First you must check all the voltages inside.
It is not an oscillator problem, it is a voltage problem. The radio has a DC DC converter similar to the one in the IC-R7000 the IC-751, (the 7000 and 7100 are very similar except the display processor and the way it works the bands high and low.
Usin the ICR7100_Service.pdf you can see the DC DC circuit. It has a +24 and a -12v regulator. After the regulator and a filter you wind up with J6 +21.6, +9, -7, and -12v. Your radio is sick if these voltages are low such as the +24 being 18v or less.
This is caused by leaked out capacitors that have gone open circuit, C21 and C22. You take off the top radio cover(carful of the speaker plug, disconnect before lifting up much. There is another cover over the DC DC unit and the whole assembly has to be lifted up and the bottom EMI cover desoldered to get to the bottom of these two capacitors.
If you have a scope you will see spikes up to 41v at D6 and no filtering at the cathode.
I have replaced these two capacitors on all 3 of these receivers.
If your radio is not working well its most likely bad capacitors. Once this radio has all its voltages and tuned to correct frequencies per the manual, it 'hears' so much better than SDR's or hand held scanners on the same antennas.
Using an SDR with a DC block does not have the same performance, noisier there.
I use CIV-Commander but it does not deal with the internal memories (900 of them). I can read all 3 on the same bus but CIV commander only handles one radio at a time. Not bad for a 30 year old radio.
 

G6FGO

Chief of Grammar Police.
Joined
Dec 6, 2024
Messages
72
Location
Gloucester, England
Thank you for that interesting information. I need to get inside mine anyway to investigate a possible dirty aerial changeover relay. Signal level on receive often drops considerably, but operating the PTT a number of time will restore it for a while. I will have a look at those voltages when I do.
 

syslabs

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Premium Subscriber
Joined
Nov 21, 2009
Messages
7
Location
AT
Hi @chris451rr,
you can program the internal memories of the IC-R7100 with RadioControl from a RadioControl memory file.

RadioControl even supports the CI-V bus feature transparently and automatically: Just install all 3 IC-R7100 devices in RadioControl, with the same serial port and baud rate (and a different CI-V address for each of them of course). No special configuration is necessary, except you have to turn off CI-V transceive in this case. This is necessary because Windows is not a real-time OS and for bus operation RadioControl needs exclusive control over the bus line. CI-V transceive counters that, leading to data garbage.

More info: https://www.radioctl.com/
 

gbusker

Newbie
Joined
Jun 8, 2025
Messages
4
I have 3 of the IC-R7100 receivers. I noticed on all of them at different times,
the frequency drifts and is off frequency. Also sensitivity is down.
And you can 're-align' all the oscillators and still have this problem. First you must check all the voltages inside.
It is not an oscillator problem, it is a voltage problem. The radio has a DC DC converter similar to the one in the IC-R7000 the IC-751, (the 7000 and 7100 are very similar except the display processor and the way it works the bands high and low.
Usin the ICR7100_Service.pdf you can see the DC DC circuit. It has a +24 and a -12v regulator. After the regulator and a filter you wind up with J6 +21.6, +9, -7, and -12v. Your radio is sick if these voltages are low such as the +24 being 18v or less.
This is caused by leaked out capacitors that have gone open circuit, C21 and C22. You take off the top radio cover(carful of the speaker plug, disconnect before lifting up much. There is another cover over the DC DC unit and the whole assembly has to be lifted up and the bottom EMI cover desoldered to get to the bottom of these two capacitors.
If you have a scope you will see spikes up to 41v at D6 and no filtering at the cathode.
I have replaced these two capacitors on all 3 of these receivers.
If your radio is not working well its most likely bad capacitors. Once this radio has all its voltages and tuned to correct frequencies per the manual, it 'hears' so much better than SDR's or hand held scanners on the same antennas.
Using an SDR with a DC block does not have the same performance, noisier there.
I use CIV-Commander but it does not deal with the internal memories (900 of them). I can read all 3 on the same bus but CIV commander only handles one radio at a time. Not bad for a 30 year old radio.
Exactly what's wrong with mine. After a long search back from the devices attached to the 24v I finally did the sensible thing and attached a scope to the output of D6. Time for the soldering iron.
 

gbusker

Newbie
Joined
Jun 8, 2025
Messages
4
Hmm I replaced the DC-DC converter caps (+24v and -12v circuits) and get the right voltages if I disconnect the -12/-7/+9/+24 connector but as soon as I connect it the -12v is pulled up to -3.5v. I have also disconnected the VCO so it's somewhere on the RF unit. Any hints welcome.
 

gbusker

Newbie
Joined
Jun 8, 2025
Messages
4
Hmm I replaced the DC-DC converter caps (+24v and -12v circuits) and get the right voltages if I disconnect the -12/-7/+9/+24 connector but as soon as I connect it the -12v is pulled up to -3.5v. I have also disconnected the VCO so it's somewhere on the RF unit. Any hints welcome.
Not quite. The 79L12 is busted. Also the DC-DC converter seems to be running at double the f I expect (~58khz) and the voltage on primary side is higher than service manual suggests. Checked ceramic capacitors, resistors.
 

kdeke

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Joined
Feb 14, 2022
Messages
20
Location
Usa
Not quite. The 79L12 is busted. Also the DC-DC converter seems to be running at double the f I expect (~58khz) and the voltage on primary side is higher than service manual suggests. Checked ceramic capacitors, resistors.
If the 7912 is running very hot, there is a shutdown mechanism that protects the 79/78 series. In my case it was a small cap that shorted the line, removed it and 7912 started working again. (on another radio of the same time period)
 

gbusker

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Joined
Jun 8, 2025
Messages
4
If the 7912 is running very hot, there is a shutdown mechanism that protects the 79/78 series. In my case it was a small cap that shorted the line, removed it and 7912 started working again. (on another radio of the same time period)
The whole DC-DC converter with its 4 outputs seems dodgy so I'm going to build a temporary PSU to bypass it to at least check if the radio itself works.
 

chris451rr

Member
Joined
Aug 1, 2008
Messages
78
Location
iowa
Hmm I replaced the DC-DC converter caps (+24v and -12v circuits) and get the right voltages if I disconnect the -12/-7/+9/+24 connector but as soon as I connect it the -12v is pulled up to -3.5v. I have also disconnected the VCO so it's somewhere on the RF unit. Any hints welcome.
I pulled --all-- the capacitors in the DC DC converter to check the values. You have other capacitors that are sub par since the current collapses the voltage. I did not need to replace regulators but you can order one and do so. Heat build up cooks out several of the other capacitors. If its run on the internal supply it needs a fan blowing across the radio.
 

wiztoms

Newbie
Joined
Aug 1, 2004
Messages
1
Hmm I replaced the DC-DC converter caps (+24v and -12v circuits) and get the right voltages if I disconnect the -12/-7/+9/+24 connector but as soon as I connect it the -12v is pulled up to -3.5v. I have also disconnected the VCO so it's somewhere on the RF unit. Any hints welcome.
Can you advise where you got these? I cannot find any information on type or mfd or where to purchase. Appreciate any help.
 

chris451rr

Member
Joined
Aug 1, 2008
Messages
78
Location
iowa
I went to Ebay and bought a capacitor kit
24value 500pcs Electrolytic Capacitor Assortment Box Kit Range 0.1uf1000uf
I have used it to repair Icoms as well as some switching power supplies.
Special values you might have to order separately.
 
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