No puedo resistirme a traer de vuelta a la vida una radio que iba al salto. Un buen Murphy A262. Este chasis apareció a mediados de los 50, justo cuando VHF-FM recién comenzaba en el Reino Unido. Uno de los primeros chasis que utilizó la válvula Mullard ECC85 recientemente desarrollada en la sección de FM como amplificador y oscilador de RF. Lo que decepciona a estos conjuntos y a muchos otros de esa época fue el uso de capdensadores HUNTS. Estas cosas eran basura incluso cuando se entregaban de fábrica.. De todas formas, acerca de 10 de estos reemplazados, el bloque de alisado vaciado y equipado con nuevos condensadores electrolíticos y sellado para que las cosas parezcan originales.. Los transformadores de I.F se modificaron y el conjunto funcionó muy bien. FM VHF agradable, sensible y con mucho volumen a través de un altavoz de 10 pulgadas, conducido por un pequeño pentodo 6P1 regordete, que necesita ponerse a dieta. El conjunto hace suficiente ruido para llenar una habitación grande.. El único problema ahora, es que la válvula del oscilador mezclador 6C9 se está volviendo difícil de encontrar.
AN UPDATE…
After working every evening for two and a half years, we started to have a few problems. Here we go!
Murphy A262C
This radio came along a few years ago and I gave it a basic restoration. Been in use almost every evening. The other day it started doing some very strange things. Unstable, bad audio, intermittent hum.
So into the shop for a quick fix. Or what I thought would be a quick fix. With the chassis removed and on the bench, I gave her some power. Dead, dial lights working but no HT. I found the EZ40 had a crack around one of the pins. Asi que, un reemplazo instalado. Now we had HT, but still no audio. After a lot of time wasting, eventually found that the chassis side of the primary winding on the output transformer had broken off. Shit. Carefully peeled back the insulation and manged to get enough copper wire to solder onto. Now we were back to the bad volume and audio. Looked to see if I had anymore hard drugs in the drawer. No.
During my first repair, I had not replaced the HUNTS capacitors that were awkward to access. Asi que, I chastised myself and replaced all the nasty bits. Audio was a bit better, more sensitive. Pero, hum and oscillations were still there. For the first time this week, I turned on the oscilloscope. Found that the main HT line had full wave ripple with audio superimposed. I had replaced the electrolytic capacitors in the past. Pero, one was open circuit! With that replaced the radio worked fantastically. It is incredible how sensitive these FM radios were. Lovely set. Replaced the mains cable with some new old stock cloth covered wire. Looks nice.
