Este artículo forma parte de un libro que el lector puede bajar gratuitamente en este sitio (El Básico de la Reparación). En esta sección los artículos se separan por tipos de defectos.

   Si el lector tiene en su casa una radio antigua, o aparece uno de ellos para reparar en su taller, verá que en lugar de los transistores lo que existen son tubos de vidrio denominados "válvulas termoiónicas", o simplemente válvulas. Estas válvulas, como las lámparas , tienen filamentos finos que pueden quemarse, cuando entonces el dispositivo deja de funcionar (fig 1).

 


 

 

   Mirando la radio conectada, las válvulas deben estar todas "encendidas" con un pequeño brillo rojizo en su interior. La ausencia de este brillo puede indicar una válvula quemada que debe ser probada y luego sustituida.

   Vea que existen dos tipos de conexión para las válvulas en radios antiguos:

- en los aparatos que utilizan transformador de fuerza, las válvulas tienen los filamentos conectados en paralelo, lo que quiere decir que si una quema el aparato deja de funcionar, pero todas las demás válvulas permanecen encendidas;

- en los aparatos que no utilizan transformadores (denominados popularmente "cola caliente") las válvulas se conectan en serie, lo que quiere decir que si una quemadura todos se apaga!

   Si una válvula está quemada y el lector a descubrir, debe llevarla a la tienda y probarla antes de comprar una nueva. En el segundo caso, existe una salida si no quiere probar todas, que es la prueba local, la cual será enseñada posteriormente. Pero, descubierta la que está mal, debe ser comprada una igual.

 

Atención: Al retirar más de una válvula del zócalo de su radio, anote la posición de cada una y el tipo, pues si hay cambio después la radio no funcionará! Válvulas son diferentes de los transistores y aparecen en diversos tipos, cada uno con su función.

 

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