Ecap Bleed Resistors

[TIMBO]

Hi guys, Bleed resistors, are they correct the way I have them. I haven't had a doubler like this before. Also do I need to one at "B" node or will the 470k/indicator lamp bleed down the Ecaps. Thanks

[Willabe]

No!

Something's wrong with it, that I've not seen drawn that way.


                      Brad   
                         
   

[TIMBO]

Hey Brad, Not sure why you are  so I will use Pete's/ Tubenit's drawings. Thanks

[darryl]

No!

Something's wrong with it

The transformer's red secondary lead ( centre tap? ) must not be connected to ground. As drawn, there are two short circuits - both from the red lead, via a diode and a fuse to a yellow lead. 


If I could make a friendly suggestion to Timbo about future projects like the current Holden/Wasp one - please keep all the details in one thread. There are at least seven threads on this forum discussing different aspects of the project, plus several more on the AGGH forum, so it becomes difficult for us to keep up with what has already been discussed.
 

[TIMBO]

Thanks Darryl, I thought the Holden Wasp was going to be a simple fixup, good suggestion. 

The RED CT is connected to ground (soldered to chassis) I traced it back to be the CT for the heaters.
The BLACK is the HT CT. (sorry for the confusion)
Redrawn schem. Thanks

[TIMBO]

SORRY guys, This topic has gone too CRAP. 

[darryl]

Back to the original question. If the indicator is an incandescent lamp, then no other bleeder is necessary. If it is a neon, then an extra bleeder from node B would be appropriate.

[Willabe]

You can't ground the PT B+ voltage winds CT AND ground the 2 diodes in the FWB. You have to go with 1 or the other.


                  Brad   

[Willabe]

Hi guys, Bleed resistors, are they correct the way I have them. I haven't had a doubler like this before.

The bleeder R's across the 2 filter caps is right, and so is where you hooked the CT up to the 2 filter caps junction.

The 2 diodes going to ground is wrong.


                    Brad   

[2deaf]

Are you sure it isn't like what I attached.

[DummyLoad]

is this for the wasp?


--pete

[eleventeen]

2deaf, delete the connection between the PT center tap and the "center tap" of your filter stack. On a 4-diode full wave bridge rectifier, the only time you use the CT of the transformer is when you are looking to achieve a + and - voltage, for example, with a +15 / -15 volt op-amp supply. Cut that connection and your circuit will work fine.

[2deaf]

2deaf, delete the connection between the PT center tap and the "center tap" of your filter stack. On a 4-diode full wave bridge rectifier, the only time you use the CT of the transformer is when you are looking to achieve a + and - voltage, for example, with a +15 / -15 volt op-amp supply. Cut that connection and your circuit will work fine.

Both supplies will work with or without the center tap.

[sluckey]

2deaf, delete the connection between the PT center tap and the "center tap" of your filter stack. On a 4-diode full wave bridge rectifier, the only time you use the CT of the transformer is when you are looking to achieve a + and - voltage, for example, with a +15 / -15 volt op-amp supply. Cut that connection and your circuit will work fine.

Not so. Connecting the CT to the junction of the two series filter caps forces the caps to charge to equal voltages.

[DummyLoad]

2deaf, delete the connection between the PT center tap and the "center tap" of your filter stack. On a 4-diode full wave bridge rectifier, the only time you use the CT of the transformer is when you are looking to achieve a + and - voltage, for example, with a +15 / -15 volt op-amp supply. Cut that connection and your circuit will work fine.

Both supplies will work with or without the center tap.

i don't believe that is correct.


--pete

[PRR]

>> Both supplies will work with or without the center tap.
> i don't believe that is correct.

I've lost track of what "both" is.

The plan posted in #1 has four wires from the winding, and is very dubious.

The plan posted in #9 is correct (but maybe not what you want!). Copy below.

The CT to FWB affair is widely used in sand-state work, particularly to get bipolar power for DC-coupled amplifiers (op-amps). See below below.

The two caps get equal voltage. They will stay near-equal for any reasonable loading. It is an interesting way to balance stacked-caps. 

Since there is only one "ground", we can put it anywhere. If we move "ground" to the negative leg, we get a positive output and a solid half-way output. See below below below. This is found on a few huge 6550/8417 amps such as 300W Bogens (600V to big plates and 300V to screens and little bottle).

NOTE that if you try this with a typical 600VCT (300-0-300VAC) winding, the output is * 840 VDC * !! For the more likely 500V DC goals, the winding should be 360V CT (180-0-180). It is rare to find a high power 360VCT winding in vintage gear.

The CT can offer a half-voltage for balancing stacked caps, but really just the first pair. Most >450V supplies will have a second cap-stack, not so easily balanced, which may want balancing resistors. And the CT does not "bleed", so you may (or may not) want bleeders anyway, which can also be the balance resistors.

[2deaf]

i don't believe that is correct.

You're joking, right?  We are talking about the physical center tap on the secondary winding, right?

[sluckey]

i don't believe that is correct.

You're joking, right?  We are talking about the physical center tap on the secondary winding, right?

I'm sure he knows how circuits work, as do you. I think he is probably unclear as to what you meant by "Both supplies will work with or without the center tap." I sure don't know which both supplies you mean. Could you clarify that?

[2deaf]

which both supplies you mean. Could you clarify that?

The quote I extracted in Reply #12 refers to TIMBO's bridge-rectified circuit for a single supply and a bridge-rectified circuit for a split +15/-15V circuit.  These are the two that I am calling "both".  I have nothing but the utmost respect for DummyLoad and I don't recall ever seeing him say anything that is wrong.  That's why I was asking him if we were talking about the same thing. 

[DummyLoad]

it's a delon FW doubler. it's simplified as two FW V doubler supplies in parallel. however, i don't believe that it's a full wave if the CT is not connected.



--pete

[2deaf]

it's a delon FW doubler. it's simplified as two FW V doubler supplies in parallel. however, i don't believe that it's a full wave if the CT is not connected.

Are we talking about the circuit in my Wasp PS.jpg attachment above which is the same as your Holden-Wasp-PS-Parallel-Doubler.pdf in the Holden/Wasp thread?

[2deaf]

it's a delon FW doubler.

This makes it clear that you are not talking about the same "both" that I am and what PRR illuminated above.  What PRR showed will work with or without the center tap and I'm pretty sure that these are the two that eleventeen meant because he said that in one case with a bridge rectifier we don't use the center tap and with the other case (+15/-15) we do. 

i don't believe that it's a full wave if the CT is not connected.

Looks full wave either way to me, but I'm no power supply expert.  If the top of the stack is connected to the plates and the middle is connected to everything else, the balance will be upset without the center tap.

The plan posted in #9 is correct (but maybe not what you want!).

DummyLoad is talking voltage doubler and TIMBO mentioned 700 volts, so the standard bridge is probably not what he wants.  They really took the hard way to get a voltage doubler as compared to my 300PS and my 400PS.  And by the way,  I moth-balled those amps because I couldn't find any 6550's that would go for any length of time at 700V.
 

[DummyLoad]

it's a a full wave CT bridge doubler. if it's making 700V, then modern tubes will have very short lifespan, if any at all.


you need the original tubes or track down some NOS 6550s.


OUUUUCHHH!!!


https://www.tubedepot.com/products/tung-sol-6550-st-nos-u-dot-s-made


--pete

[TIMBO]

Hi guys, These are the 6550s

[DummyLoad]

Hi guys, These are the 6550s

beautiful!


--pete

[TIMBO]

Hey DL, Thanks for all the input.
I'm about ready to fire ( ) this one up.
I will start without tubes in and get some basic voltages.
I want to check the bias range as well. Thanks

[DummyLoad]

cool!

did you install the bleed resistors? 


will you post some clips?


 



--pete