Front panel troubleshooting


allgyer@...
 

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



Steve W3AHL
 

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



allgyer@...
 

The Logic Board is repaired and seems to be working fine. Replaced the CPU, serial EPROM, and the 3.3 volt regulator that supplies the keep alive circuit. QC-ing the CPU, a 144 pin chip, was a bear. In the end had to check each pin with one needle probe on the board land and the other LIGHTLY on the pin where it enters the chip. Found at least a half dozen poorly soldered pins (my work) that had intermittent or no connectivity.

After that the display worked and I could hear but only really strong signals. Turns out prior work (not mine) had scraped a capacitor  in the first IF circuit off the board and I was losing about 30 dB of signal on everything but WFM mode which worked normally. Replaced the 0402 smd and now the receiver shows S9 or better on all bands with a -73 dBm input signal and all modes work. So far so good...... it is coming back to life.

Next TRANSMIT. So far it goes into transmit mode but no power at all out on HF/6M, about 2.5 watts out on 2m, and less than a watt on 450. Not out of the woods yet but very promising.

Warren - WA8TOD