PSU Diode upgrade & Cath Foll conversion

[buddam]

Hi All

having a few problems with this. It's recommended to upgrade the BYV96E diodes, independently of Cath Foll mod. There's a huge choice at RS, but I've found a Cree CSD05120A which measures 1200V, 5A. I wondered if this was ok?

And, could these not also replace the D5 and D6 when doing the CF mod. This would be massive overkill but I suppose there's no problem with that.

Whether I can get any from Cree's UK distributors is another matter!

Thanks

Adrian

[Max N]

Hi Adrian
D5 & D6 are not used as switches in this circuit, they are used like xeners to provide 0.6v each (using the forward voltage drop of the diodes), ie 5v regulator plus 0.6 plus 0.6 = 6.2v.
So no point in choosing soft-switch or shottky in that location
Max

[Global]

Adrian

Where did you find the High Voltage Cree Schottkys?

Thanks

Mark

[Black Stuart]

Adrian,
have a look at the FAQ section - on diodes, there's plenty of choice there.

Black Stuart

[buddam]

Thanks for the replies,

Global & Stuart - I read the diode stuff on the BB, searched for Cree, & linked to UK distributors. I've emailed them asking for 10. If & when they reply Global I can increase my oder. If you want to do it yourself the website IIRC is www.neutronltd.

Max - my notes, taken from postings on the WAD BB, say D5 & 6 can be uprated to UF4007 or UF 4001 or similar rating Shottkies, eg MBR150 or 160. Will Schottkies do any damage here? Should I stick to zeners?

From the old WAD Site I've copied this:

"D5/6 are 1N4001 50v 1A so I`d replace them with similar rating schottkies such as MBR150 or 160 or the hyperfast equivalent, UF4001". In fact the questioner want with UF 4007 & seemed very pleased.


Thanks
Adrian

[NickG]

Do not use Shottkies there, the operation relies on there forward voltage drop being 0.6v, if you replace them with a diode having a lower voltage drop the heater voltage will be wrong.

By all means change them to UF types, but as someone else has said, these diodes are constantly forward biased, they do not switch off, so there is (IMHO) no point of using other types.

The max forward voltage drop of MBR150 is 0.55v so your heater voltage will at most be 6.1v maybe less as the diodes may have a lower voltage drop, as the data sheet value is the max at 0.1A and they will be passing less than that.

[Global]

Hi Adrian

I tried the distributors some time ago. They would not deal with me unless I ordered 500 diodes!

I hope they have reviewed this or can tell you where to buy retail.

I would indeed be interested in geting some!

Mark

[Richard]

Mark, Adrian,

I had a set of Crees in my Kit88 and sold it with them in dispite it being a 10 minute job to swap them out (on a daughter board). Point being they were good but no better than 2 or 3 other types we listened to. Perhaps once a certain point is reached it may be a case that it is "good enough" and any extra improvement, if any, is lost in the general circuit noise.

Anyway, I know it's a challenge to track them down yourselves to have a listen but if you want to save money and effort IR Hexfreds are vailable from RS,

HFA08TB120 8A 1200V trr 28ns Ultrafast Ultrasoft Recovery TO247AC (square 2 legs) RS 395-4477 £5.24
HFA08TB60 8A 600V trr 55ns Ultrafast Ultrasoft Recovery TO247AC (square 2 legs) RS 244-9889 £2.69
Data sheet, http://www.chipcatalog.com/Datasheet...5107A28477.htm

Rich

[buddam]

Thanks Nick & Richard

I'll steer clear of Schottkies

Richard, are the HFA08TB60 (the others are rathe expensive) you refer to replacements for the BYV96E? Or can they also be used as D5/6?


Thanks

[Global]

I would use HT Schottkys purely for the sake of consistency if I were changing out all the rectifier diodes in an amp since I would use them in all other places. My philosophy would survive a premium of, maybe, 15%!

I last used IXYS FREDs for HT and they are absolutely fine but I don't have any left!

Mark