[IC-7000] Re: Front panel troubleshooting


Warren Allgyer <allgyer@...>
 

Thanks Steve. We are down to the dreaded Logic Board on this one. The CPU is running and making system clock but none of the other clock outputs are doing anything. At the moment I have nothing in the screen and nothing into or out of the encoder. Wish I had an extension cable so I could get to the bottom of the logic board while it is running. I have seen more difficult from a serviceability standpoint but not many!

Warren - WA8TOD


On Sep 8, 2017, at 4:13 PM, w3ahl@... [ic7000] <ic7000@...> wrote:

 

There are several errors in the schematics and you just found another one. I traced the PCB artwork in the Service Manual and the signal that is labeled GND is actually an audio return "ground" for the AFO audio output.  It goes to the speaker jack on the right edge of the Display unit.  


So it appears that the only DC ground is indeed the YGND, which isn't a very good design.  But I'm sure there's a reason they had to make a compromise.

As to your display symptom, I haven't had to work on a unit that had that problem.  If you have an external monitor that will take an NTSC signal, then plug it into the rear video output jack.  If you get a picture, then the video signal from the main unit is good and the problem is probably in the display head.  If you don't get a picture on the external monitor, then there is a problem with video encoder or LCD control circuits on the Logic board.

Steve, W3AHL

---In ic7000@..., wrote :

I am working on a "hangar queen" IC-7000 with multiple problems. I am wondering if others who have been deep inside the 7K have noted this issue:

While the Service Manual a connection of both YGND and GND to the board foil on the Display Board, there is no such connection in my unit. The ground return for the entire front panel is via the shield on the video cable. There is no ground continuity between the Main Unit and the Display Unit unless the video cable is connected. One result of this is the unit cannot be turned on without the video cable plugged into the Main Unit.

This is perhaps a fault in my unit but I have painstakingly traced the lands on both sides of the Display Unit and I find no connection between the two grounds as indicated on the schematic.

Is this a known issue/feature or is this perhaps a symptom of my problem(s).

Problems at the moment are a display that remains in black, intermittently displaying unlocked video.

Warren Allgyer - WA8TOD



Paul Hansen
 

I’ve done a lot of work on 7000’s. As far as I know, there were no extender cables available to the service centers allowing the lifting of the logic unit. You would have to fabricate them from scratch. There are only a couple of circuits in the logic unit normally serviced by Icom. They are the battery and the CI-V components. An update applied to earlier units in an attempt to halt driver unit oscillation changed some components in the logic unit. Otherwise, the logic unit was normally just replaced. It was considered an unrepairable part. Add to this, there is a version of the logic unit that is known as faulty. Icom replaced them outright under product warranty but that has long since expired.

 

Your best move at this point is to find another known good 7000. Swap the logic units to see what happens. That will confirm the track you’re on is the right one. Do the same thing with the control heads. However, only put the good head on your radio. There is a common failure in the control head that can damage the radio. It’s repairable but why add more work to the deal. I have never damaged a logic unit from swapping it between radios so don’t worry about that.

 

Thank you,

 

Paul W. Hansen, W6XA

 

 

From: ic7000@... [mailto:ic7000@...]
Sent: September 08, 2017 22:32
To: ic7000@...
Subject: Re: [IC-7000] Re: Front panel troubleshooting

 




Thanks Steve. We are down to the dreaded Logic Board on this one. The CPU is running and making system clock but none of the other clock outputs are doing anything. At the moment I have nothing in the screen and nothing into or out of the encoder. Wish I had an extension cable so I could get to the bottom of the logic board while it is running. I have seen more difficult from a serviceability standpoint but not many!

 

Warren - WA8TOD


On Sep 8, 2017, at 4:13 PM, w3ahl@... [ic7000] <ic7000@...> wrote:

 

There are several errors in the schematics and you just found another one. I traced the PCB artwork in the Service Manual and the signal that is labeled GND is actually an audio return "ground" for the AFO audio output.  It goes to the speaker jack on the right edge of the Display unit.  

 

So it appears that the only DC ground is indeed the YGND, which isn't a very good design.  But I'm sure there's a reason they had to make a compromise.

 

As to your display symptom, I haven't had to work on a unit that had that problem.  If you have an external monitor that will take an NTSC signal, then plug it into the rear video output jack.  If you get a picture, then the video signal from the main unit is good and the problem is probably in the display head.  If you don't get a picture on the external monitor, then there is a problem with video encoder or LCD control circuits on the Logic board.

 

Steve, W3AHL

---In ic7000@..., <allgyer@...> wrote :

I am working on a "hangar queen" IC-7000 with multiple problems. I am wondering if others who have been deep inside the 7K have noted this issue:

While the Service Manual a connection of both YGND and GND to the board foil on the Display Board, there is no such connection in my unit. The ground return for the entire front panel is via the shield on the video cable. There is no ground continuity between the Main Unit and the Display Unit unless the video cable is connected. One result of this is the unit cannot be turned on without the video cable plugged into the Main Unit.

This is perhaps a fault in my unit but I have painstakingly traced the lands on both sides of the Display Unit and I find no connection between the two grounds as indicated on the schematic.

Is this a known! issue/feature or is this perhaps a symptom of my problem(s).

Problems at the moment are a display that remains in black, intermittently displaying unlocked video.

Warren Allgyer - WA8TOD