UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - My first valve radio project

julie_m · 28th Dec 2016, 1:26 am

Comgratulations! Sorry, been away with other things, you know how it gets ..... Anyway, well done on getting it to this state! You have established that there is a path for audio, so there can't be much more wrong with it now .....

Indications earlier seemed to point towards a faulty power transformer, which is why I didn't go into more detail about the rectifier "bodge"; but it it had looked as though the AZ31 were faulty and the power transformer sound, I would have suggested getting two 1N4007 diodes and two 220Ω, 3W resistors; soldering a resistor in series with the anode lead of each diode; joining the two cathodes together, and this junction to C26 (Trader) / C1 (Manufacturers') positive; and the other ends of the two resistors to pins 4 and 6 of the AZ31 socket. This arrangement uses silicon diodes to replace the diode valves within the AZ31. The series resistors are there to make up for the fact that a silicon diode is a better conductor, when the current is in its preferred direction, than a diode valve.

But that's probably not something you will need to bother with now.

28th Dec 2016, 1:26 am	#155
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: My first valve radio project - Philips 462A Comgratulations! Sorry, been away with other things, you know how it gets ..... Anyway, well done on getting it to this state! You have established that there is a path for audio, so there can't be much more wrong with it now ..... Indications earlier seemed to point towards a faulty power transformer, which is why I didn't go into more detail about the rectifier "bodge"; but it it had looked as though the AZ31 were faulty and the power transformer sound, I would have suggested getting two 1N4007 diodes and two 220Ω, 3W resistors; soldering a resistor in series with the anode lead of each diode; joining the two cathodes together, and this junction to C26 (Trader) / C1 (Manufacturers') positive; and the other ends of the two resistors to pins 4 and 6 of the AZ31 socket. This arrangement uses silicon diodes to replace the diode valves within the AZ31. The series resistors are there to make up for the fact that a silicon diode is a better conductor, when the current is in its preferred direction, than a diode valve. But that's probably not something you will need to bother with now. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.