Icom 756 unit. Odd Transmit problem any help would be appreciated. (kf8bdt)

[shocker03p4]

I bought this unit used. It is set up using a Kenwood pf-50 power supply. I have two dipoles for antennas. long line all hf channels and a 10 meter inverted v. Both good swr below 2.5

Problem

When I go to transmit on 10 meters I will key the mic and the needle doesn't move the transit red light comes on, and the fan starts, it's like I have a dummy load on. We (an extra class friend) hooked a watt meter up and on and we hit rtty and tested on each band up and down and was reading 80 watts out.
but if you to USB or LSB we see nothing.

any ideas, please

Jeff

 

[FlatlandBusa]

No modulation? Problem only on 10?

 

[SuperLid]

I bought this unit used. It is set up using a Kenwood pf-50 power supply. I have two dipoles for antennas. long line all hf channels and a 10 meter inverted v. Both good swr below 2.5

Problem

When I go to transmit on 10 meters I will key the mic and the needle doesn't move the transit red light comes on, and the fan starts, it's like I have a dummy load on. We (an extra class friend) hooked a watt meter up and on and we hit rtty and tested on each band up and down and was reading 80 watts out.
but if you to USB or LSB we see nothing.

any ideas, please

Jeff

Sounds like no modulation, check microphone.

 

[shocker03p4]

No modulation? Problem only on 10?

With a dummy load right now my transit meter on rtty, FM , Am hits 80 watts which looks great.
if I hit ssb goes up to 20 watts and drops back down. when we tested I could not reach out 12 miles away on 10 simplex. I can't get anyone to receive me to check.

all bands are the same

 

[shocker03p4]

Sounds like no modulation, check microphone.

bought new cheap one same have now a sm50 same

 

[shocker03p4]

It seems like a simple adjustment i am missing.

 

[BC Coyote]

The SWR is way too high at 2.5 The radios SWR protection is probably kicking in.

My Old Icom 735 would start to fold back output power at an SWR of 1.5 and would be down to only about 50% output at SWR of 2.0 and down to 25% output by the time SWR got up to 2.5 or so. Higher SWR than that and zero output.......

 

[nomadradio]

Is this problem confined to 10 meters only?

Or does this occur on other bands?

Or for that matter, only when using the 10-meter antenna? What the radio does into a dummy load could be quite instructive.

73

 

[Hurricane145]

What the radio does into a dummy load could be quite instructive.

Yes. put it on a dummy load and see what results you have. It is THE best place to start troubleshooting.
Any new info about it? It's been a while. Did you get it resolved?