ARLA/CLUSTER: Avaria radio Kenwood TS 440S

[Tiago Santos]

Parece que a avaria é conhecida! Condensadores.

Kenwood TS-440S (TS 440 S TS440S) Displays dots on certain bands


The reason for this is well known and covered elsewhere. One VCO was not
locking - easy to find which one it is but why....??


All DC Voltages were OK so probably not transistor/bias. Must be the
conductive goo syndrome or a faulty capacitor/coil.
Once the RF board is out of the radio how do you tell?
No power on the board anymore so no way to run the oscillator to find out if
it's off freq or just won't start.

I decided to compare with a GDO the dips I got with the faulty VCO and it's
neighbours next door - about 5MHz higher/lower in freq.

It turned out when measuring the main tuned circuits I could see a good dip
on them but on the this VCO's transistor base dip was flat/absent. On
neighbour VCOs dip was still visible although not very deep.

I changed (one at a time) capacitors around the tuned circuit. On replacing
47pF capacitor in series with VCO tuning diode dip returned with same depth
as all the others. Board was put back in radio and now all FB!

Suggest using GDO to check oscillator tuned circuit Qs when board is out of
the radio and can't be powered up.


2009/2/16 Tiago Santos <ct2hcq  gmail.com>

>
> Boa noite, deixo aqui um relato da avaria que tenho no meu radio de HF.
> Funciona bem em todas as bandas recepção e emissão, passado algum tempo
> depois de ligado (5 minutos), o display deixa de dar os numeros da
> frequencia em que
> estava e passa a ter apenas uns pontos como se fosse os pontos que separam
> os mhz dos khz só que em todo o ecra. Deixa de ter recepção e emissão em
> todas as bandas e em todos os modos. Quando mudo de frequencia, volta a
> aparecer a mesma no ecrã, mas continua sem receber nada, e logo de seguida
> volta a aparecer a mesma avaria.
> Isto acontece parece-me quando ele aquece, sem que seja necessário estar
> em
>
> emissão. Alguem sabe o que possa ser??
>
> --
> Cumprimentos,
> Tiago Santos
> CT2HCQ Setúbal Portugal
>
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>


-- 
Cumprimentos,
Tiago Santos
CT2HCQ Setúbal Portugal
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