Icom: IC-7100 not powering up LDG tuner

[KM4CXB]

One day, I turned on my radio and the LDG IT-100 would not power up. I had a bad cable and tried to replace the pins in the molex connector on the cable and was unsuccessful. All I succeeded in doing was blowing the 5 amp fuse on the radio. Replaced the fuse, ordered a new cable and installed it and nothing. Tested the output from the radio through the cable on pins 3 and 4 on the molex end and on pins 1 and 4 on the round DIN connector and got 13+ volts. Now I figured my tuner was bad. So I bought a new tuner, hooked everything up and same thing. Tuner won't power up. At this point, I'm out of my depth. I know that there is "start" on pin 5 and "key" on pin 6 but I have no idea how to test it, much less fix it. I'm afraid that when I blew that fuse I killed something else. Advice please. Should I send my radio in for repair?

 

[prcguy]

Can you power up the tuner from a different source like using the coaxial power socket if it has one?

 

[KM4CXB]

Can you power up the tuner from a different source like using the coaxial power socket if it has one?

It just has the standard coax connections. There is an accessory jack, but the only way I know to hook up this particular tuner is with the dedicated tuner control cable. I may try to find out if there is a way to use the accessory jack but that's way off the beaten path for this tuner.

 

[prcguy]

It just has the standard coax connections. There is an accessory jack, but the only way I know to hook up this particular tuner is with the dedicated tuner control cable. I may try to find out if there is a way to use the accessory jack but that's way off the beaten path for this tuner.

Probably the IT-100 model. I would remove the cover, find the 12v bus inside and see if 12v is making it to the board. You mentioned there is 12v at the radio end, this will help rule out a bad cable, bad connector or bad tuner.

When you measured 12v on the radio end were you measuring from the ground to hot on the molex connector or chassis ground to the hot on the molex? If there is a circuit board ground trace feeding the molex the trace could have smoked when you had a bad cable.

 

[KM4CXB]

Ok, thanks for helping. To be clearer, I checked 12v output at the radio and at the control cable end where it connects to the tuner. I've got 2 tuners and neither one will respond so I'm quite sure the problem is on the radio.

Taking the cover off the tuner, the feed from the control cable goes to the bottom side of the main board. I don't feel comfortable disassembling the tuner to test on a 12v bus as it would be quite delicate with so many connections to ground, coax in and out, etc.

I believe the radio is not raising a signal on the start pin. At this point I'm looking for a repair technician who knows Icom and take it in.

 

[prcguy]

Ok, thanks for helping. To be clearer, I checked 12v output at the radio and at the control cable end where it connects to the tuner. I've got 2 tuners and neither one will respond so I'm quite sure the problem is on the radio.

Taking the cover off the tuner, the feed from the control cable goes to the bottom side of the main board. I don't feel comfortable disassembling the tuner to test on a 12v bus as it would be quite delicate with so many connections to ground, coax in and out, etc.

I believe the radio is not raising a signal on the start pin. At this point I'm looking for a repair technician who knows Icom and take it in.

You can probe the start pin with a volt meter and push the tune button to see what's there with the tuner attached. I don't know if its supposed to go high or but I could test mine and let you know.