Found schematic 50W EL34 AB. Needs help...

[DAK808]

Basically you can, but that PS has regulated screen grid voltage too, that is not necessary required if +Ub is some 450 V and of course not with UL.

Hi, i would be very interested in checking out your PS with the regulated screen voltage. Thank you

 

[artosalo]

Here it comes.

 

[piano3]

artosalo; does GU50 work well on only 520V?

 

[Zekk]

Here it comes.

Can you please show a pic of that power supply? Or better still, u've a board to sell me?

Thanks!

 

[artosalo]

Here is the photo of that power supply. The size of the board is 100 x 100 mm.

does GU50 work well on only 520V?

As far as remember the combination +Ub = 520 V and Rload = 4k was fully OK.
I tested that circuit some 5 years ago.

 

[artosalo]

My test circuit was this:

 

[artosalo]

I found my test memos of GU-50 PP amplifier.
Some remarks:
- Test conditions: +Ub = 480 V, Ug2 = 350 V, Ug1 = -55 V, Ik (idle) = 50 mA/tube, Rload = 4k
- Pout = 24,5 V @ 8 ohms---> 75 W max.
- Ug2 had to be raised to 350 V to get sufficient power from quite low impedance OPT (4k)
- Optimum conditions would be + Ub = 500...550 V and Rload = 6k to 8k.

 

[piano3]

Thanks, artosalo.

 

[DAK808]

I found my test memos of GU-50 PP amplifier.
Some remarks:
- Test conditions: +Ub = 480 V, Ug2 = 350 V, Ug1 = -55 V, Ik (idle) = 50 mA/tube, Rload = 4k
- Pout = 24,5 V @ 8 ohms---> 75 W max.
- Ug2 had to be raised to 350 V to get sufficient power from quite low impedance OPT (4k)
- Optimum conditions would be + Ub = 500...550 V and Rload = 6k to 8k.

Hi Art, i am just considering the regulated G2 part of your schematic. I am thinking of trying regulated G2 voltage for a SEP amp. My raw B+ is about 460vdc so that seems to be in your voltage range. I don't have any D3 , D4. Those are 200v 3w zeners? What is their purpose? I also see a D5, 12v zener. I am a novice at SS so , i wonder again, what is its purpose.
Some builders, who prefer to not put any SS devices into their amps would worry about the effects of having the zeners and the IRF820 being in direct contact with the G2 grid and having a sonic imprint. Since my amp is SE is that something to be concerned with. thanks again. 808

 

[artosalo]

Are you also going to use GU-50 to make the SEP amplifier?

D3 and D4 are 200 V/3 W zeners and their purpose is to generate stable (~400 V) reference for the g2 voltage adjustment.
D5 is for protecting purpose of IRF820.

If you wish you can "isolate" the IRF820 from the G2 with 1k resistors.

Remember that with regulated Ug2, the Ug1 must be regulated too, if fixed bias is used.

 

[jazbo8]

OT posts removed.