Re: Help diagnosing no transmit problem.

Mike,
I would check to see if you have 13.8 volts on your PA board. If it is
there, check for 13.8 volts on the drain of each of the MRF255 HF power
transistors.
There is a relay that controls power to the PA board, RL3001. If the relay
or its driver fail, you won't get power to the output transistors.
Good luck
Mike M.
KU4QO

On Wed, May 9, 2018 at 11:38 AM, [email protected] [FT100] <
[email protected]> wrote:

>
>
> My old FT-100D has worked well for years (original owner) and, suddenly,
> zero output on HF and VHF.
>
> Thinking it was the PA transistors I replaced the MRF755's with NOS ones
> but problem remained the same.
>
> Using a shortwave radio I hear perfect SSB TX on HF when held close to the
> unit, and I also hear perfect VHF FM TX when an HT is held close to the
> set. Levels are VERY low.
>
> The idle current is 1.2A in RCV, which is normal. The current increases to
> about 2.4A in transmit, both HF and VHF. Bias adjustment in HF has no
> effect for the PA transistors.
>
> I've removed the PA deck and checked the resistors on the underside, that,
> for some, were a problem. It 'seems' to me that there is some 'master'
> shutoff that is closing ALL the transmit higher power circuits in both HF
> and in VHF/UHF.
>
> Is there a circuit as I described?
>
> Is there a part failure that would cause both RF amps to become
> inoperative?
>
> What voltages should I look for? I used to be a whiz at this but find that
> my skills have diminished with disuse!
>
> Bummer.
>
> Any help, or guidance, or reference to other sources, would be appreciated
>
> Mike VE3EQP .....>
>
> 
>