6D22s damper diodes.

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#1 6D22s damper diodes.

Post by pre65 »

I'm a bit confused about 6D22s, with regard to what Svetlana call Vb.

They say, you can heat a 6D22s on the same supply as other tubes up to a Vb of 600v.

http://www.drtube.com/datasheets/6d22s-sed1997.pdf
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#2

Post by Paul Barker »

yes because they are tv damper diodes they expect you to stand them high off ground and because they are for TV's they expected them to be on a series string of all valves in the set with the same current, like Mullard PL valves. So they have made the heater insulation extremely thick so that the high voltage potential of the heaters doesn't short to the cathode.
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#3

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So, if the cathode is above 600v the heater potential needs raising ?
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#4

Post by Paul Barker »

Well the HT comes out of the cathode so it will be at your peak rectified voltage 1.414 X RMS less drop across diode. If you are using standard valve full wave with a centre tapped transformer, the heater is allowed to be 600v negative to the cathode so your transformer would have to be less than 424v at the absolute limit.

The PIV which is the negative peak which would try to pull current in reverse through the diode can be as much as 6,000v so you are safe there.

If you wanted to exceed 424v you could tie the cathode to the heater supply say through a centre tap but DO NOT Ground it! BANG!
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#5

Post by pre65 »

At the moment, on 833a, I have HT of 950v and that is tied to just one side of the 6.3v at each 6D22s. (part of a hybrid bridge)

The reason I'm asking is that one of the 6D22s on one monoblock started flashing inside a while ago, and I've yet to sort it out. I was chatting to Andrew I about it today and we ended up confusing each other.

Making a centre tap would seem a better idea, resistors still 100R ? And presumably at 950v standard resistors are no go ?
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#6

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pre65 wrote:At the moment, on 833a, I have HT of 950v and that is tied to just one side of the 6.3v at each 6D22s. (part of a hybrid bridge)

The reason I'm asking is that one of the 6D22s on one monoblock started flashing inside a while ago, and I've yet to sort it out. I was chatting to Andrew I about it today and we ended up confusing each other.

Making a centre tap would seem a better idea, resistors still 100R ? And presumably at 950v standard resistors are no go ?
Well, if you intend to put 950v across a 100R resistor, then most resistors will have a problem.
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#7

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Nick wrote:
Well, if you intend to put 950v across a 100R resistor, then most resistors will have a problem.
Forgive my ignorance, I thought "normal" resistors were only good up to 600v ish, so what are my options ?

Is the way I do it now incorrect ? It is connecting full HT to one side of the 6.3v circuit. The two 6D22s on each amp are on a separate 6.3v winding on the transformer.
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#8

Post by Paul Barker »

I can't see the need for a centre tap at the rectifier stage as you will do smoothing afterwards.

whatever happened before I can't see what tying to one end of the 6.3v winding had to do with it.
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#9

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Paul Barker wrote: whatever happened before I can't see what tying to one end of the 6.3v winding had to do with it.
That's excellent Paul, all I really wanted to find out. Thanks. :D
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#10

Post by Paul Barker »

The thick insulation can tolerate 600v so 6.3v isn't a challenge for it.
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#11

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Paul Barker wrote:The thick insulation can tolerate 600v so 6.3v isn't a challenge for it.
Oh dear. :? :?

But if one side is at 950v ?
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#12

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pre65 wrote:
Paul Barker wrote:The thick insulation can tolerate 600v so 6.3v isn't a challenge for it.
Oh dear. :? :?

But if one side is at 950v ?
One side of what?

The cathode and the heater are the only things that matter here, there is no 0v, there is just the difference in voltage between the cathode and the heater.
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#13

Post by Paul Barker »

This is as hard for Phil as picking a browser is for me. :lol: :lol:
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#14

Post by pre65 »

Nick wrote:
pre65 wrote:
Paul Barker wrote:The thick insulation can tolerate 600v so 6.3v isn't a challenge for it.
Oh dear. :? :?

But if one side is at 950v ?
One side of what?

The cathode and the heater are the only things that matter here, there is no 0v, there is just the difference in voltage between the cathode and the heater.
There are two wires going to the heater of the 6D22s damper diode. One of those wires is also connected to HT at approx 950v.

Would a diagram help. :?
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#15

Post by Paul Barker »

Phil the cathode stands at the B+ voltage, if you connect the heater to it at one end that stands at B+ voltage, the other heater pin stands at B+ voltage -6.3v.

You can even use the same heater transformer for the opposite end of a centre tapped winding.

But if you bridge rectify you have to make it hybrid, you would need 3 transformers or two silicon diodes.
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