30-11-2015, 05:13 PM
(27-11-2015, 06:04 PM)pwdrive Wrote: You've got the HMV going, that's good, some radios are pigs to work on some aren't so bad, keep at it.
Don't forget to post a question If there's anything regarding to radios etc that you're not too sure of.
Lawrence.
Thanks, Lawrence. To be honest, I had a hard time believing it. The first time I powered on, I didn't get much of a result. The dim bulb tester was a bit red so I assumed something was wrong and that I'd screwed up somewhere. I'd gotten a bit of a hum from the speaker but no sign of stations. Later I found out if the dim bulb tester only goes orange and doesn't glare, it should be O.K. to plug into full voltage so I did. I finally connected the aerial lead and then I did get the one station and was pretty stunned. It was Radio 4 but there was a bit of hum and the volume was weak. Still, I was very happy to have gotten some result.
After that, I was checking the aerial and started to check resistances and joints. I finally planned to just work my way through the circuit with a hope to improve on reception as I plodded ahead. I was in no rush.
The test that was most productive was the Volume Potentiometer readings on the grid of the DDT. Placing the meter on the Megohm setting, you can hold one probe to the volume pot lug and the other probe to the grid. As the volume rises with the turn of the switch, the Ohms will creep up to 500 K. I eventually found there were capacitors in the circuit around here so their function was quite important for bypassing R.F. I tried changing one in the grid circuit plus another capacitor elsewhere and that then solved the problem of poor volume and partial reception.
It was hard to believe I finally had a working radio because I was a bit sceptical over not having access to much of the set and the fact I was limited by my approach not to fully dismantle the set. However, fortunately, it all worked out.
The work done is as follows:
(1) Repair of mains supply to transformer and fuses + holders (which were too dirty to conduct).
(2) Cleaning of wiring and components as well as chassis and all switches. Full cleaning of chassis that was covered in dust and dirt. Cleaning of tube bases.
(3) New potentiometer to replace one that was broken and corroded.
(4) Rewiring of rectifier tube.
(5) New 16mF smoothing can as former had been sparking and seemed dodgy.
(6) New AF coupling capacitors and all worn or suspect capacitors changed, except the Picofarad types.
(7) New wiring where necessary.
Work To Be Done Is:
(1) Restoration of cabinet.
(2) Need to stencil in 2 glass waveband slats with lost data.
(3) Restringing of tuning mechanism.
(4) All scale lamps to be replaced and holders cleaned.
