SF4007 vs 1n5408 rectifier diodes

[TugaTweaker]

Hi all !

An evening trying to change two 1n5408 rectifiers diodes over HFA08TB60 in a Audio Note P2SE valve amp power supply . Failure .
P. S. Transformer output 2x 310v , the HFA08TB60 are intended to reach 600v , i have blown two , i think they don t
fit the purpose , maybe i m wrong .
Do the SF4007 diodes that are 1000v 1a worth a try .
Please help !

 

[EC8010]

STTA512F is very robust. 5A, 1200V, soft recovery.

 

[TugaTweaker]

SF4007 vs 1n5408

Thanks for the advice EC8010! Meanwhile i discovered at RS Components the HFA08TB120 1200v too , and somebody at
Audio Asylum suggesting that the cathode base of the to220a
package could act as a RF antenna , that s hard to take .

Regards

 

[EC8010]

Yes, the TO220 base would act as an aerial if not on a heatsink. But bear in mind that the signal is 440V peak. Just how signifcant is the picked-up RF compared to the self-generated?

 

[TugaTweaker]

sf4007 vs ...

Thanks again .

" But bear in mind that the signal is 440V peak "

Now , i begin to ask myself , if the HFA08TB60 Freds max 600v
and the signal is 440v peak , what happened ? A misconnection?
I applied 330 VAC at pin 2 anode , then the supply shorted because of a blown diode two times , until i replaced the 1n5408
and everything normalized . That s only the first round , i will
get those 1200v ones then i will get the job done .

Regards

 

[EC8010]

One-offs vs production

For a centre-tapped supply, each diode sees twice the peak voltage, so you need 2 x 310 x root 2 = 877V. The voltage that you use at the output of the rectifier is 440V peak (well, 438V).

Technically, you only need 900V diodes. So 1kV rated types would be fine. Except for spikes. In practice, it makes a lot of sense to use higher voltage/higher current types unless you have the time to do the testing in your own circuit to find out if more marginal types are OK.

 

[TugaTweaker]

EC8010 ! I Dont know how to thank you ! Now its clear for me .

God bless you !

 

[EC8010]

You're welcome.