HFU HF Underground
Technical Topics => Equipment => Topic started by: Roykirk on December 07, 2019, 0401 UTC
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Purchased a used Icom IC-735 that arrived today. Seller said it worked fine. I used to own an IC-735, so I'm pretty familiar with them, but it's also been a long time and maybe I'm just forgetting something basic. When hooked up to either a dummy load or an antenna, there is zero transmit signal. When the mic is keyed, the meter pegs hard left, and won't budge with any voice level or mic gain or RF power setting. Monitoring from a Tecsun shortwave received nearby, there is absolutely no signal. Receive seems to work fine.
Not a huge deal if this sounds like it's dead as it has a 30 day return. But I just don't want to go through the trouble of returning it if I'm missing something basic here that would cause it to not transmit. I'm thinking it could be something as simple as a bad mic, or something as bad as a blown PF.
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What's the meter set to read?
What mode are you using when testing?
Key it in cw, am, or fm mode and see if anything happens.
What is the mic gain and rf power out set to?
Use the tx switch on the rig rather than the mic to see if it works.
Those are great little rigs, and if you replace the bad varicaps they last forever.
https://www.qsl.net/icom/oldicomfaq/ic-735.html
https://www.youtube.com/watch?v=PTugqZDVDW0
http://www.hampedia.net/icom/ic-735.php
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Got it figured out. Simple oversight.
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The one I had I replaced the CFW455HT am bandwidth filter with an IT version as they rejected 5KHz hfbc beat notes while swling, the HT version passed the beat notes but had better audio because it was wider.
Also replaced the prod det diodes with schottky hot carriers as well as the am det diode, reduced distortion compared to the 1N60s. Great little rigs.
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Got it figured out. Simple oversight.
Could you please, please tell the rest of us what that simple oversight was? I was given a used IC-735, and am experiencing the exact same issue you described.
Many thanks in advance! :)
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Got it figured out. Simple oversight.
Could you please, please tell the rest of us what that simple oversight was? I was given a used IC-735, and am experiencing the exact same issue you described.
Many thanks in advance! :)
As noted here....
https://forums.radioreference.com/threads/new-ic-735.359237/
....check the mic plug for a lose wire.