Ralph Spracklin
Forum Participant

Hey John and all
I ordered a bunch of the 1N5000 series,diodes and rebuilt the Rectifier. I think that using 1N5000 series was the right choice. Thanks for the suggestion John.

This German, Arabella 58 set was indeed a challenge. It was taxing my troubleshooting skills to the limit. I’d fix one problem, only to find there is yet another hurdle to overcome. Somebody in the past had messed around with this set and lost their way, although their soldering skills were excellent. At first I was having a problem, where only the FM Module tube was warming up. I solved the problem with that, only to find out that I had the Push Pull Output tubes were notburning as hot as they normally should be. Heater voltage being pulled down. Then I discovered that the ECC82 tube, which is a dual triode, was running very cold, with no sign of receiving power. My question was why is this happening? Well here is what I discovered. What I thought was an ECC82 tube, had been substituted with a 12AU7 tube, which, by the way, is an Identical tube, both of course have the 12 volt designation. As I never ran into a tube line-up where all tube filaments, which had only a 6.3 Volt supply from the Power Transformer, so I wondered why there would be a 12 Volt tube in the line-up. In my mind this would explain why the tube would run cold.. I did not realize at the time, that this 12AU7 had a three pin filament set-up, which allowed it to be also run as a Six Volt Tube. So here’s the grabber, in order to use it in a Six Volt filament tube line-up, one has to utilize that third Filament Pin (Pin 9) on those two mentioned tubes, which allowed it to function as a Centre Tap, between the two internal split filaments, connecting them in parallel, thus acting as a single 6 Volt Filament, with a 300 mA draw. Of course by leaving the number 9 pin open, those tubes would operate as a 12 volt filament. Such anomalies do arise in the world of radio restoration, but this one had thrown me for a looper.

Two days later and the radio is now working fine, although I still have to lubricate the turn table assembly, and touch-up the Cabinet. I did not have replace, even one of the Capacitors or Resistors, or tubes on this unit. I was glad about that as there were easily around three hundred of these compoments used in this chassis. It had the potential of being one expensive restoration. Total cost to me in parts, $20.00.