[Yaesu] [ft991] RE: [Yaesu-FT-991-group] FT991 PA failure and serial number range

Thu May 25 15:14:01 EDT 2017

Ron,
Are you saying Yaesu set the bias incorrectly and maybe one reason for PA failures??? I am assuming there is a PA bias adjustment in the 991.
If so are you recommending we go inside our 991s and adjust the bias???
73, ron, n9ee/r a know code Extra
Ron Wright, N9EE/R
BSEE
Micro Computer Concepts
352-683-4476
mccrpt at tampabay.rr.com
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From: ft991 at yahoogroups.com <ft991 at yahoogroups.com> on behalf of ka0ryt1 ka0ryt1 at yahoo.com [ft991] <ft991 at yahoogroups.com>
Sent: Thursday, May 25, 2017 5:00 AM
To: Yaesu-FT-991-group at yahoogroups.com; ft991 at yahoogroups.com; yaesu_ft991 at yahoogroups.com; Yaesu-FT-991-group at yahoogroups.com; yaesu reflector; yaesu at contesting.com
Subject: [ft991] RE: [Yaesu-FT-991-group] FT991 PA failure and serial number range
Hello group ! I am really wanting to share that with the lower power output such as HF WSJTX . The HF PA biasing does make a huge difference especially in relation to the bias being set at room temperature compared to the bias at the warmed up temperatures achieved at operating WSJTX at QRP power levels ( read inefficient ) .... The 1.5 amp per transistor biasing does go up to 1.6 - 1.7 amps per transistor at inefficient heat levels . Again , I recommend you set your HF PA Bias at 1 amp per transistor ...... it's your rig . ( before anyone,wants to blast me about setting the HF PA transistor biasing lower than the yaesu specs - do your homework and see what the transistor manufacturer is using ) ..... I also have an extra fan that is piggy back on the existing fan that is running all the time - it minimizes the thermal 'runaway' of the BIASING ..... your mileage may vary ... Ron KA0RYT EN 35ct
>From my Android phone on T-Mobile. The first nationwide 4G network.

-------- Original message --------
From: "John Geiger af5cc2 at gmail.com [Yaesu-FT-991-group]" <Yaesu-FT-991-group at yahoogroups.com>
Date: 05/25/2017 10:21 AM (GMT-06:00)
To: ft991 at yahoogroups.com,yaesu_ft991 at yahoogroups.com, Yaesu-FT-991-group at yahoogroups.com,yaesu reflector <yaesu at mailman.qth.net>, yaesu at contesting.com
Subject: [Yaesu-FT-991-group] FT991 PA failure and serial number range
I have seen quite a few mentions of final transistor failure in the Yaesu FT991 transceiver. Is this a problem with all FT991s, or is there a serial number range where this problem has been fixed? If I am looking for a used FT991, what serial numbers should I avoid?
Any other comments good or bad about the FT991?
73 John AF5CC
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Posted by: ka0ryt1 <ka0ryt1 at yahoo.com>
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