06-28-2014, 11:10 AM
Hi,
Thank you for such a detailed and speedy reply to my Email.
I obtained my 47 several years ago and kept it collecting dust on the shelf till now, when I decided to resurrect it to life. Someone has apparently attempted to convert it to AC in the past but has given up on it after tinkering about and doing some rewiring which just made things a bit more complicated . I know that there are several ways to proceed and I have decided to abandon the series filament approach which appears too complex since not all tube filaments have the same current requirement, requiring compensating, heavy resistors. I have thus mounted a separate, small transformer for the filaments of the 6.3 volt tubes and a 25 volt transformer for the two "43" output tubes.
For the high voltage supply, I have introduced a full wave bridge rectifier in a straight forward supply circuit with two electrolytics and a filter choke. There are two chokes in the circuit already and I hope to be able to use one of them for this purpose, but I have not yet figured out a good way to do this. Hope you can suggest something.
My other problem is that the schematic for the set shows the output transformer in a typical set up with a center tap to the B+ supply, however the actual transformer on the speaker has no center tap, thus I don't think I can use it for the push pull set up shown on the schematic. I was thinking of wiring the two "43" output tubes in some sort of a parallel configuration. (hope you have a suggestion there).
Anyway, this seems a cumbersome way to go about it for a set that may not be worth the trouble, however, I am retired with plenty of time on my hands and this keeps me challenged and off the streets.
Thank you for such a detailed and speedy reply to my Email.
I obtained my 47 several years ago and kept it collecting dust on the shelf till now, when I decided to resurrect it to life. Someone has apparently attempted to convert it to AC in the past but has given up on it after tinkering about and doing some rewiring which just made things a bit more complicated . I know that there are several ways to proceed and I have decided to abandon the series filament approach which appears too complex since not all tube filaments have the same current requirement, requiring compensating, heavy resistors. I have thus mounted a separate, small transformer for the filaments of the 6.3 volt tubes and a 25 volt transformer for the two "43" output tubes.
For the high voltage supply, I have introduced a full wave bridge rectifier in a straight forward supply circuit with two electrolytics and a filter choke. There are two chokes in the circuit already and I hope to be able to use one of them for this purpose, but I have not yet figured out a good way to do this. Hope you can suggest something.
My other problem is that the schematic for the set shows the output transformer in a typical set up with a center tap to the B+ supply, however the actual transformer on the speaker has no center tap, thus I don't think I can use it for the push pull set up shown on the schematic. I was thinking of wiring the two "43" output tubes in some sort of a parallel configuration. (hope you have a suggestion there).
Anyway, this seems a cumbersome way to go about it for a set that may not be worth the trouble, however, I am retired with plenty of time on my hands and this keeps me challenged and off the streets.
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