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Old 20th February 2005, 11:12 AM   #1
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Default Damper Diode Musings

Considerable praise has been lavished on vacuum damper diodes. While I'm not going to naysay, I have been doing some thinking.

In the TV application, dampers are dealing with strong pulses, as opposed to continuous current. The published data sheets reflect that fact. It seems to me that, in audio PSUs, damper diodes should be used with cap. I/P filters and that the caps. used should be at the limit the devices can tolerate. Used that way, the tubes are working in a pulsed environment not too different from TV. Used as indicated, the amount of draw derating needed would be reduced.
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Old 20th February 2005, 11:57 AM   #2
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There's also the part in most of the datasheets where it is explcitly stated that "Operation of this tube as a power rectifier is not reccomended"...
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Old 20th February 2005, 12:38 PM   #3
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I had the same pair of 6CJ3 dampers running for nearly three years in various circuits.

The datasheet I have shows a maximum average current rating. Staying under this is a good idea, but I'm not sure why it would require derating.

There is no warning against using these as half-wave recitifiers in the RCA 6CJ3 datasheet.

Slow turn on, low voltage drop and heavy duty...what more could you want?

That said, I wish people wouldn't use them. I used to be able to get them from AES for around 50 US cents each when they were in the sale flyer. Now they're never in there.
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Old 20th February 2005, 01:02 PM   #4
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Remarks have been made about the need to derate. Also, it seems intuitive that significant derating is in order if choke I/P filtration, with its continuous draw, is employed.

In addition to the NOS types, SED offers the 6D22S in "current" production.
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Old 20th February 2005, 03:07 PM   #5
jlsem is offline jlsem  United States
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Quote:
In the TV application, dampers are dealing with strong pulses, as opposed to continuous current. The published data sheets reflect that fact. It seems to me that, in audio PSUs, damper diodes should be used with cap. I/P filters and that the caps. used should be at the limit the devices can tolerate. Used that way, the tubes are working in a pulsed environment not too different from TV. Used as indicated, the amount of draw derating needed would be reduced.
Damper diodes are necessarily "rated" for pulse duty only. They are diodes designed to withstand it. They are manufactured with a special cathode coating process they prevents cathode stripping under heavy pulse conditions. The data sheets give a value for maximum continuous dc output current and I see no reason for derating. The cathode coatings are also exceptionally heavy which would seem to indicate long life. Mine are long-lived at the maximum current rating.

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There's also the part in most of the datasheets where it is explcitly stated that "Operation of this tube as a power rectifier is not reccomended"...
I have read a lot of data sheets on many diode dampers from several manufacturers and have never seen this disclaimer. On whose data sheets did you read this message?

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Old 20th February 2005, 05:23 PM   #6
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So, let me get this straight.... you are worried about using a tube designed for pure torture, in rather lazy conditions?

Why!?

Tim
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Old 20th February 2005, 05:37 PM   #7
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Damper diodes are necessarily "rated" for pulse duty only.
I meant are NOT...

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Old 20th February 2005, 06:15 PM   #8
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Originally posted by Sch3mat1c
So, let me get this straight.... you are worried about using a tube designed for pure torture, in rather lazy conditions?

Why!?

Tim

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Old 20th February 2005, 10:47 PM   #9
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The warning is generally on Sylvania and GE datasheets for damper diodes (6AU4, 6DA4 etc...) but missing from later types like the compactron 6AX3.

It may be possible that it's just a ploy on the manufacturer's behalf to keep people buying 5AR4s and 6CA4s instead of a pair of (possibly cheaper?) damper diodes - Apart from this I see no clear reason why they can't be used for power rectification. High pulse current capability, low voltage drop, softer switching, slow turnon - what more could you want?
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Old 20th February 2005, 11:45 PM   #10
jlsem is offline jlsem  United States
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It may be possible that it's just a ploy on the manufacturer's behalf to keep people buying 5AR4s and 6CA4s instead of a pair of (possibly cheaper?) damper diodes
Let's see - a pair of 6AU4's in 1958 would have been $6.10. A Mullard GZ34 (with metal base no less) was $3.50.

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The warning is generally on Sylvania and GE datasheets for damper diodes (6AU4, 6DA4 etc...) but missing from later types like the compactron 6AX3.
These tubes may not have had the advanced cathode coating method used in later DD's but still needed long heater warm-up periods because of heavy emission material layer (not unlike Bendix Red Bank rectifiers). In other words, a long warm-up need coupled with ordinary bonding technique of cathode material could have resulted in stripping if a time delay circuit was not employed. Bendix rectifiers' cathodes do look a lot like a damper diode's and they specify warm-up periods of 45 seconds or more before applying B+.

John
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