Solid state rectifier??

[TerrySmith]

As much as I hate SS stuff, the ST70 pulls too much current for single tube (5AR4) rectifier.

Rather than hard wiring diodes, I've taken old metal tubes, gutted them, and soldered in diodes using pins 4, 6, and 8. Then paint the metal shell and reinstall it on the base. The end result is it sorta looks like a tube! Haven't tried it on a '70 yet.

I was wondering what kind of voltages to expect at initial turn on. Will have a cl-80 installed. My main concern is will the AES 40-80-30-20 quad cap handle the SS rectifier?

[sorenj07]

I'm not positive but I'd expect the 5AR4 to drop around 25V. Correct me if I'm wrong, though, I've never owned any Dynaco equipment

[erichayes]

Hi all,

Good guesstimate, Soren. The problem with high vacuum (as opposed to mercury) rectifiers is that the forward voltage drop is dependant on the current draw. You can count on 15 volts being lost right out of the chute, but 50 volts is not uncommon when the rectifier is maxxing out.

Silicon rectifiers, on the other hand, have a 0.6 volt forward drop regardless of current draw, up to their maximum rating. You can work backward from that to determine what amunt of resistance to use to sop up the excess forward voltage.

The inrush limiter should be sized so that there's a maximum voltage drop of around 5% on the secondary when warm.

[mesherm]

Terry,
Just get a Weber Copper Cap.
http://www.webervst.com/ccap.html
I've had a WZ68 (equal to two 5AR4s) in my KT88 triode amp for over a year now with no probs.
Mike

[hilldweller]

Terry,
Just get a Weber Copper Cap.
http://www.webervst.com/ccap.html
I've had a WV68 (equal to two 5AR4s) in my KT88 triode amp for over a year now with no probs.
Mike

How About Those Weber Coper Tube SS Rects. I Hear They Are Good For Guitar Amps With The Sag Thing And All. Do You Think They Would Be A Good Choice For The ST-70??? Yellow_Light_Colorz_PDT_14

[soundmasterg]

I use the Weber Copper Caps in several guitar and bass amps, including a Sunn 200S which is very similar to a Dynaco Mk.3. They work and sound fine, and it makes the load easier on you power transformer since there is no filament current to supply. I highly recommend them. For the Stereo 70, I'd recommend the WZ68.

Also, just a note.....there is no need to capitallize every word in your posts. Just proper names and the first word in a sentence are necessary. It would make your posts easier to read....


Greg