Tech Question: Low Tx power on FT-857

cockpitbob

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I never paid much attention to the current meter on my 12V supply running my FT-857 until now. I think for everything but FM my FT-857 is a QRP rig. I'm hoping one of you gurus can tell me if I need to send it in for service.

I just got done with a series of tests into a dummy load with o-scope and into a different dummy load with cross-needle meter. They both tell the same story.

Tx set to 7.1MHz, 40W:
* FM - carrier power = 43W. (all OK).
* CW - carrier power = 3.5W (should be 40W, shouldn't it?)
* LSB - pk envelope pwr = 3.5W yelling into the mic
* AM - carrier power = 0.2W with close to 100% modulation yelling into the mic. (manual says factory set to 25W)

For SSB I've tried setting the mic gain to 100% and the AF speech processor to 100%. I can't get more than 3.5W pk with the Tx pwr set to 40W. When I set the meter to monitor the ALC (auto level control) the meter shows zero level control no matter how much I yell at the mic.

I've been through all the settings twice. I even did full CPU reset.

So, do I send it in for service? Where, Yaesu or somewhere else?

Thanks,
Bob
 
I don't have any working knowledge of this radio, but I own one that's sitting on a table waiting to be put into service so I have an interest in this.

If the ALC isn't kicking in when you yell, I wonder if it's a problem with your mic. Since AM/SSB vary the output level based on your speech level but FM doesn't this seems like it would further support my theory.
 
I'm an electrical engineer and actually design analog circuits for a living, but this problem looks too weird for me. All powers except FM are low, including the AM carrier which should be 25% of the power setting with no voice. Even CW is low which should just be a full strenght carrier. If I start at a 5W setting the power will increase but power is low and stops increasing at about a 30W setting, Yet, FM is perfect (set for 50W and I get 50W) which tells me it isn't the output stage but something earlier.

I've made lots of QSOs lately, both SSB and CW. I thought I wasn't being heard as well as I thought I should so I got out the test gear. So, it's a functioning radio, just a QRP one[thinking].

I've read through a bunch of eHam reviews of repair shops and sent an email to one this a.m. But if anyone has personal knowledge of a shop experienced with Yaesus I would appreciate a recommendation.
 
I've heard Universal Radio repairs radios in house. I'm not sure what their policy is for radios not bought from them though.


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For SSB I've tried setting the mic gain to 100% and the AF speech processor to 100%. I can't get more than 3.5W pk with the Tx pwr set to 40W. When I set the meter to monitor the ALC (auto level control) the meter shows zero level control no matter how much I yell at the mic.
(For a while now I've wondered whether a rig's DTMF support is a good source of
dual-tone input audio, for measuring SSB power...)
 
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