JE EL34 Build

[pre65]

You probably don't need a heat sink at your current, but the casings would still be live.

[colin.hepburn]

Originally Posted by pre65

I think that's right.

Colin, you do like making things difficult.

What's wrong with more conventional diodes ?

I may well have 4 spare if you want something more conventional.

Hi Philip
yep when I build my 12B4A headphone amp it have standard 1Ns Diodes on it which at time I change out for the TO220 type Mur 820 I think fast recovery which sound much better tighter faster sound the poor man’s hexfred but when I did these there were a different make and the schematic for the U8100E was confusing me but sorted now thanks for the offer

[A Stuart]

rect2.gif

further playing on GIMP - it is a bit like Photoshop but it's FREE . Note, even without heatsinks there will be live sticking up bits.

[colin.hepburn]

Originally Posted by A Stuart

Attachment 1986

further playing on GIMP - it is a bit like Photoshop but it's FREE . Note, even without heatsinks there will be live sticking up bits.

Ah Yes that’s what I was trying to visualise them as but i was getting Anode and cathode mixed up the live taps will be insulated in some way
PS thanks for the software tip as well
Cheers

[colin.hepburn]

Hi All
Well its be some time now but this stalled Build is moving again
got the PSU build and working first time
Required HT is 380volts @ 67mA got 378volts in Duncan’s PSU Checking the psu with DMM no load I get a HT of 518volts is this about right or to high for no load

[pre65]

On the Duncans simulation, try reducing the load to a lower current (ma) and see how the voltage increases. That should give you an idea.

And (or) work out what the load is in resistance terms (ohms law) and put a resistor across the PSU to simulate the amp load and see what the voltage comes down to. Should be about 5K6 ohms (5.6K) and minimum of 25W.

[colin.hepburn]

Hi Philip
Making thinks difficult well yes many have said this in the past just the way I am I guess
I just thought that 518 volts was I bit high for no load HT with caps of 450volts volts not sure what the formula is to work out no load voltages

The Diodes
I just used two diodes making a full wave rec the diode are Mur 8100E/1000volt 8 amp fast recovery easier to use two than working with four single T0220 type diodes
Part two The Amp Build will start to day

[Richard]

Hi Colin, there isn't really an easy way to calculate working voltage as it will depend on your mains TX rating and regulation. The no-load figure is in the ballpark and can be handled by the EL34s so I'd just connect psu to both amp channels now and see how it drops if the 450V caps are still ok. If you do decide to keep it the caps will need uprating voltage-wise as they will be hit by overvoltage at cold switch on and will probably fail eventually. Does your mains TX have the heater windings for a valve rect btw? If so a valve rect would might be the answer and will drop typically 60v. That with the load across the choke and on the TX may be about right.

[colin.hepburn]

Hi Richard
Thanks for your reply yep the TX has 5 volt for tube rec but its only 2.5 amps my Tube rec draws 3amps I think so used the solid-state diode as I thought it was easier the 450 volt caps are still OK for now

[Richard]

Hi Colin, GZ34 1.9A, indirect too so it would turn on more slowly