[ICOM] ICOM-R7000

[Steve]

I agree with your comments.

I do take it for granted that a person willing to attempt repair of 
their own gear is going to perform basic troubleshooting steps before 
ordering anything!
The very first thing I check is the power supply stage(s) for proper 
voltage levels. That is assuming that the really basic things have 
been checked first like, is the device plugged in, power switch on, etc!

For the R7000, it is pretty well documented that the majority of 
failures today are indeed dried out caps due to the age of these 
radios. It's a pretty easy radio to quickly test the main supply and 
then the dc-dc converter input and output voltage levels.
A bad cap on the converter board can usually be seen easily with just 
a DVM. It does not take much to load down those outputs well out of tolerance.
If power all checks out, then I will start injecting signals into 
whatever stage I suspect as the culprit and follow the path to the 
problem. Of course a thorough visual check is done first looking for 
obvious signs of problems.
Cracked boards, signs of arcing, cold or poor solder joints (if that 
side of the board can be seen), burnt components near the antenna 
input or B+ lines etc.

I also often take it for granted that a person has good soldering 
skills and the proper tools to do the job.

When the R7000 was put on the market, I'd likely never suspect bad 
lytics with the symptoms the OP is having. I'd agree 100% that there 
is a problem in the RF, IF stage etc.
But these receivers are over 30 years old now so the chance of a DC 
failure increases greatly.

You are correct that there are not many, if any, electrolytic caps on 
some of the RF/IF boards. If they are there, they are usually not a 
part of the RF or IF circuit. I think one of the links that Gary 
posted said the radio does have around 140 electrolytic caps in it 
though! That would be a LOT of caps to change that may not be bad.
I would suggest that the OP only change those at the main supply and 
the dc-dc converter stage if he chooses to just go in blindly and 
change caps without testing. More so, the caps on the converter 
board. The main supply will brute force past a bad cap there but I 
bet it would show up as hum in the audio as those caps are mostly 
filtering caps. I think there are some zener regulated stages prior 
to the dc converter that would probably draw voltage down if there 
are bad lytics there. Then of course it has some common three legged 
regulators with lytic filter caps. Those would probably brute force 
past a bad cap also.
I think the failure I saw the most was either a -12 or +24 volt 
output failure from the dc-dc converter. The dc-dc converter powers 
the RF board in the R7000 as well as a few other circuits.

One unrelated failure I've seen more than once is a faulty power 
switch. They use a DPST switch. One side switches the +13.8 VDC 
regulated output side from the main supply for use when running off 
external power and the other side switches the neutral leg of the AC 
input receptacle to the main transformer. My switches were failing on 
the DC side of its contacts. Not total failure but I could see it in 
the meter backlight. The lamps brightness would change pretty much if 
you kept constant pressure on the power switch. I was showing almost 
4 volts of voltage drop across the switch. So my regulated 13.8 volts 
was dipping down to nearly 10 volts.
Icom wanted nearly $40 dollars for a new switch! The same switch is 
used in the R71 series and I think it is in the R9000 also but not 
positive on that. I know it is also used in several other Icom 
transceivers as well.
My solution was to simply move the DC wires over to the other set of 
contacts as I powered the radios from external power so the AC 
contacts were not used and they tested good. The other set of 
contacts had 0.3 volts of drop max.
I finally found a matching switch on eBay for something cheap like $3 
dollars so I bought several and installed them so I could run from AC 
again. The originals were made by ALPS and seemed to be quality 
switches with a 5 amp at 250VAC rating but no DC rating. The 
replacements I found have a 7 amp at 250VAC rating so I assume they also 
may hold up longer on the DC side. They are funny as one countries 
cert lab rates the same switch at 10 amps at 250vac and another only 
lists it at 5A at 250vac But the same symbol as on the ALPS switch 
says 7amps at 250vac. The wire lugs on the new switches are thicker 
and wider than the ALPS have. No manufacturer name on the new 
switches though. The new switches are also DPDT so they are a tad 
longer and may not fit all Icom models


At 06:33 PM 6/16/2013, you wrote:
>While I have no dispute with the theories put forward thus far, I think it
>would be a grievous error to start ordering parts without doing any sort of
>troubleshooting.
>
>Several possible reasons for the failure mode you are experiencing have been
>suggested. To embark on a wholesale replacement of components without so
>much as a test result seems like a bad plan.
>
>It is possible that electrolytic caps could be a contributing factor, most
>RF stages don't have many. Electrolytics tend to be in the DC circuitry.
>
>Troubleshooting the symptoms described requires a suitable signal generator,
>injection probe and 15 minutes to inject signal and see where the path goes
>bad. Once the faulty stage is found, DC voltage checks and some resistance
>checks should point clearly at the actual problem.
>
>I don't disagree that an elderly receiver could benefit from an electrolytic
>cap "overhaul." It seems sensible to first find the real problem and correct
>that before creating new ones by replacing parts wholesale.
>
>Good luck no matter what path you choose.
>
>73,
>
>Frank N. Haas KB4T
>Florida
>
>
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