ICOM IC-R7000 Radio Electrolytic Capacitor Overhaul

From Frank
frolektrics electronics notes & projects

 

I have recently replaced all the electrolytics my ICOM IC R-7000 VHF/UHF receiver.

The receivers and transceivers of this ICOM radio series are getting on a bit in age. They were manufactured in the early eighties and now weird faults are beginning to show themselves as the electrolytic capacitors dry out and lose capacity and increase esr.

If you have an R7000 that…

• Never has had an overhaul
• Suffers a decrease in sensitivity and increase in noise
• VFD display digits blinking/dim/missing

Then there’s a good chance that your radio needs some new caps and a bit of TLC

The best way to tackle the overhaul is to take the “shotgun” approach and replace all of the electro’s in one hit. This is a lot of work but the job can be easily done providing your well prepared. Actually this statement is true for most things in life. It took me 10Hrs all up to do it.

The first thing you’ll need to do is acquire all the capacitors for the job. There’s 114 of them to replace and you can get the specs from the IC-R7000 service manual (Off the web – do a Google search for it if you haven’t got it).

I took the easy route and got a kit of capacitors from the ve3pvs web store on eBay. I recommend purchasing the kit as for $40 it will save you a lot of list writing, spec comparing and running around. Here is a photo of the kit shown left.

Tools that are also essential for the job include a temperature controlled soldering station and a vacuum desoldering tool. I cannot stress the importance of having a proper de-soldering tool as solder-wick just won’t cut it over the long haul with this job. You will get fatigued and start making silly mistakes like dwelling too long with heat over the one spot or wiping the solder-wick with too much pressure laterally across the PCB. Both scenarios are likely to cause lifting of some of the tracks. The PCB is single sided phenolic and the pcb trace adhesive isn’t as good as contemporary fibreglass boards. To re-iterate, beg, borrow or steal a proper DE-SOLDERING TOOL (I was lucky enough to be able to borrow one from work over the Christmas break).

One last thing to be thought of is the method of performing this job. You will need a method that will enable to pick up from where you left off during interruptions to the work. I have found that using a list that orders capacitors by pcb will allow one to fold out a pcb from the chassis of the radio and strike the capacitors one by one off the list as you replace them. I also found that marking the tops of new capacitors with a black texta also aids in identifying the ones that are yet to be replaced on the pcb.

Here is the strikeout list I made up in PDF form -> R7000ElectroChangeoutChecklist

In short, this is the process…

1. Fold out a pcb from the wiring harness to work on
2. Change a capacitor
3. Strike off the list and mark the top of the cap in black
4. Goto step two until all the caps for that board are changed
5. Goto step one until all the boards have been worked on

I found that a couple of the caps have been mounted on the solder side of the board (late manufacturing revision?). And that the capacitors for the InfraRed pcb mounted on the front panel must be mounted on the reverse side of the board as the ones they replace are much smaller.

I hope I have made it easier for anyone taking on this overhaul job in the future and that you get many more years of service from the receiver.