FT2000 : Limiter les effets des retours HF

Cette vidéo concerne certains FT2000. Alors pour les adeptes d'amplificateur d'émission HF derrière le poste, peut-être est-il souhaitable de regarder cette vidéo ainsi que de vérifier le numéro de série (cf. article sur le sujet - Cliquer ici )


(nota : Me contacter si la vidéo n'est plus disponible)

Voici un document très intéressant sur les retours HF (en anglais) :
http://k9yc.com/RFI-Ham.pdf

et le commentaire de l'auteur au sujet du FT2000 :

The FT-2000 has the infamous Pin 1 problem.  Refer to page 5 of Jim's document.

Here is how I tested my copper tape fix.  I knew what configuration caused the preamps to blow.  In my case it was to have something plugged into the rear panel key jack and run 1Kw on 20m.  I could blow it every time. I actually confirmed my setup by running a test and promptly blowing a transistor.  (Over my testing I replaced 8 of them)

 Knowing I had a good test case set up.  I installed the copper tape and new preamp transistors.  I ran the same transmit test with the exact same configuration.  Nothing blew.  I did this several times to be sure.  So based on that testing I am pretty sure the problem won't reoccur.  But it does depend on how good a job of grounding with the copper tape you do.  You could use aluminum tape but you can't solder to it. So it doesn't work for every connector.  And remember the glue on the back of the tape is an insulator.  Also note that aluminum anodizing is an insulator.  I always assume bare metal has some sort of coating on it. 

And if you do blow the transistors you most likely will have blown other things as well.  I sent my radio back to Yaesu after replacing the preamp transistors and  the mixers in both receivers. Yaesu replaced 11 other components.  Including discrete parts like capacitors.  I know that the Yaesu repair center in CA ran out of the parts to repair this problem for a while.  Which shows how many people are affected.
Although I got a list of what parts were replaced they did not tell me schematic reference for the part.  ie., 0.1Uf cap but no C2103 designator.

I have had email conversations with many hams worldwide about this issue.  I am heartbroken to hear hams, in countries where the radio costs an average person's annual salary, tell me their radio is blown up.  It is interesting on how Japanese manufacturers won't admit to ever making an engineering error.  I have gone through this sort of fight with Kenwood too. 

I wish every ham with this problem all the best in fixing their rigs.  If it was me I would install the copper tape fix.  I sold the radio with it installed.

73,
Mike

En résumé... Il est préférable d'utiliser le FT2000 non suivi d'un amplificateur de puissance d'émission.
Dans le cas contraire, le risque d'avoir des problèmes n'est pas totalement nul et je ne peux que conseiller
la modification présente sur la vidéo afin de se prémunir le mieux possible contre ce risque de destruction
de l'étage d'entrée de réception.