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1-9 of 9 messages
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IC706MKIIG FIXED IN TX
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by EA4BQN on November 16, 2006
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My IC706MKIIG has remained in TX mode and cannot be switched to RX. The CPU has been reset but not results. There is not the voltage of 8V at pin 3 of ACC socket, the voltage is about 1 V.I have revised the components around this circuit and they all seem to be OK. Any help ? Thanks
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RE: IC706MKIIG FIXED IN TX
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by K6ACJ on November 16, 2006
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Diodes and transistors perform many of the circuit switching functions and being surface mount, can be difficult to work with. Unless you have the ways and means to locate the component, consider sending the 706 in for service.
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RE: IC706MKIIG FIXED IN TX
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by KC8VWM on November 16, 2006
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Just for clarification.
Have you elimininated the possibility of a microphone or mic connector short as the cause of the problem?
73
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RE: IC706MKIIG FIXED IN TX
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by EA4BQN on November 16, 2006
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Thanks for your replies but the microphone is out
I checked some resistors, diodes and transistors and apparently they worked, so
I'll keep on checking as far as my knowledges allow
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RE: IC706MKIIG FIXED IN TX
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by KC8VWM on November 16, 2006
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Might be a long shot but sometimes resetting the radio back to factory settings doesn't necessarily reboot the entire CPU.
Disconnect all power sources and try removing the internal CPU battery and let the radio sit around a while with the power switch in the "on" position. Of course with no external power attached to the radio. This will force the CPU to forget everything for a while. Be sure it sits around long enough that it completely discharges any power left in any capacitors to ensure a complete CPU reboot.
After a while, replace the battery, connect the radio to a power source and perform a "reset" on the radio.
Who knows.. this might do something.
73
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RE: IC706MKIIG FIXED IN TX
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by W5HTW on November 16, 2006
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Unfortunately the 706 uses EEPROM, not battery, but that does not mean you should not try letting the radio sit for 2-3 days. If there has been a static discharge through the antenna input, it can do weird things to the radio, but if it is left alone, that charge can drain off. I have not had that happen with a 706 but I have sure had it happen with other things!! Like my VCR and a DVD recorder. Both, after several hours of sitting disconnected and unplugged, did recover.
Pin 3 in the ACC jack is a "ground to transmit" pin, and should go to ground when the PTT switch is pressed. Normally this pin has a .5 to .8 v on it when not grounded or in transmit. Measure this with a high impedance meter and see if that voltage is there.
Not likely to be anything that would be resolved by a full CPU reset, but if you can get that done it is worth a try. If it doesn't work, I'd let the radio sit (as described above) for a couple of days, and then try a second CPU rest. Total reset, not just one that clears the memories.
Remove the detachable panel. If you have the cable for remote operation, try the radio with the cable. There have been a couple of reports of shorts in the plug on the detachable front panel. Tighten all the screws on that panel.
Put it in SSB mode, and check the RF power output. Should be zero, even if the TX light is on. IF you see output, perhaps there is something in the audio chain trigger the VOX. Turn the VOX, COMP off.
You probably can't switch modes with it in TX but if you can, try the above and try other modes as well.
If you don't have the 8 vdc on pin 1 of the ACC socket, the 8 v regulator may be blown. That often (but not always) comes from attempting to use an older microphone not designed for use with the 706. Some of them ground the 8V which blow the regulator. A fairly common problem. People hook a D104 to the radio, and goodby 8V regulator.
My guess is the 8v regulator. Sometimes they just "go."
Good luck.
Ed
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RE: IC706MKIIG FIXED IN TX
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by K0BG on November 17, 2006
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If the 8 V regulator was defective, there wouldn't be any transmit power.
This problem usually happens when an external device is connected to pin 3 of the accessory jack, that has 12 volts applied to it. For example, using the port to close a relay with the hot to pin 8.
The fix is not an easy one os the switching transistor is surface mounted. Unless you have the tools to replace it, I'd sent it off for repair.
Alan, KØBG
www.k0bg.com
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RE: IC706MKIIG FIXED IN TX
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by EA4BQN on November 17, 2006
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Thanks to everybody
THE PROBLEM IS ALREADY SOLVED
Checking into the schematic of the Filter Unit where the PTT socket is, and measuring the various voltages around pin 3 of this socket, I verified that the moving pin of RL16 did not have the 8 V in the position of not doing any PTT(microphone, etc). Immediately I suspected of Q11- 2sd1623, that makes the 8 V switching when PTT is done
it was crossed between emitter and collector and therefore in RX the 8 V voltage did not appear at the collector.
Bye for now
Jose Miguel
Ea4bqn
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RE: IC706MKIIG FIXED IN TX
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by EA4BQN on November 17, 2006
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Thanks to everybody
THE PROBLEM IS ALREADY SOLVED
Checking into the schematic of the Filter Unit where the PTT socket is, and measuring the various voltages around pin 3 of this socket, I verified that the moving pin of RL16 did not have the 8 V in the position of not doing any PTT(microphone, etc). Immediately I suspected of Q11- 2sd1623, that makes the 8 V switching when PTT is done
it was crossed between emitter and collector and therefore in RX the 8 V voltage did not appear at the collector.
Then carefully with the soldering iron I removed it and solder another one found at the shack even of different type, but it worked
Bye for now
Jose Miguel
Ea4bqn
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