Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: shooter on December 04, 2016, 07:59:46 pm
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k, so the logins, cats and dogs are all good, we're having a debate on the PS. The schematic is my "redraw" without zeners etc. here's a link to the original thread that has the original schematic
http://el34world.com/Forum/index.php?topic=21186.0 (http://el34world.com/Forum/index.php?topic=21186.0)
On my "re-draw" it shows - to me - a voltage doubler config. With the PS that we used I opted to eliminate the CT to center of caps, the 4 diodes, and just use a bridge grounded. All the DC volts on the rail hit the target volts (within reason).
Bills dilemma, question, if the original schematic is a voltage doubler, what would you expect the PS secondary's to be.
the one he's using is 185-0-185, loaded B+ is 480vdc (schematic below except with bridge grounded, CT not connected)
thanks
dave
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The original circuit is not a doubler. It's just a FWB.
Your redraw shows the center of both cap stacks tied together. You should not do that. Each of those stacks has a different B+ on them.
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> shows - to me - a voltage doubler
No.
It *will* show twice the DCV of the same CT winding used with a 2-diode rectifier affair. Maybe that is confusing you?
I get 518V from the full 185+185=370VAC winding. 480V is likely loaded.
> center of both cap stacks tied together. You should not do that. Each of those stacks has a different B+ on them.
Very true.
In THIS case: they are "only 390r apart". And it *appears* the big current does not flow on that. Taking ~~30mA of G2 and small-tube current in 390r, they are only 12V apart.
Further, if caps are 250V we already in trouble at first high line voltage. If 350V, each cap is 100V shy of rating, so another half-12V is no big deal. But if they are 300V rating..... hmmm. Yes, all this stuff has to be worked out before plug-in or certainly before it goes to client.
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It *will* show twice the DCV of the same CT winding used with a 2-diode rectifier affair. Maybe that is confusing you?
The whole "original PS" confused me!, that's why I opted for a plastic bridge, 4 wires, no brother-in-law diode arrays between B+ n screen.
I get 518V from the full 185+185=370VAC winding. 480V is likely loaded.
That's were she dialed in at, we hit all the #'s correctly on the B+ taps, AC ripple good at each tap. the only major issue left is 60hz hum and weather changing back to exact copy of original PS solves it.
You should not do that
sorry, drawing error, not actually wired that way :think1:
Thank you.