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Solid State delay on turn on relay.

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Over the course of the time I have been on this board there has been a lot of talk about using a SS rectifier and the worry of cathode stripping and all the associated horrors involved in the use of the nasty animal.

So, I will pose this thought. Would the use of a delay on turn on relay be of a benefit? I was going thru my shelves of junk I ran across a Narional Controls Corporation Model T 1K-120-461 adjustable timer with a range of 1.2-120 seconds delay. This timer when fed a source of 120V will delay the activation of its relay that would control the secondary main from the transformer to the SS rectifier. Thus controled B+ operation after the heaters are on and the tube warmed up. The relay is rated at 10A @ 240V. I'm sure it would withstand higher B+ without a problem.
Also its a octal mount unit that will fit in most rectifier sockets if there is room enough for its body. Just rewire and lable the socket for this device only and I would think it would work.

Any thoughts?:smash:
 
Quote:

Believe it or not, Amperite still manufactures the same vacuum tube time delay relays they made in the 30s. Another option to consider.

Wodgy do you happen to have a link to the information?

Quote:

That should work fine. But what is your application? Most tubes have no problems with SS rectifiers. Only large directly heated tubes and mercury vapour tubes actually need a turn-on delay, as far as I know...


I was under the impression or misimpression that Solid state rectifiers caused problems in any setup and caused cathode stripping. I figured tube rectifiers were better because of the voltage delay upon startup.:confused: So, I was wrong?
 
burnedfingers said:
I was under the impression or misimpression that Solid state rectifiers caused problems in any setup and caused cathode stripping. I figured tube rectifiers were better because of the voltage delay upon startup.:confused: So, I was wrong?
No, not quite. SS rectifiers can cause cathode stripping. But the problem, as I understand it, is completely theoretical in "normal" tubes. Big transmitter tubes are a different matter, but I guess your not building a transmitter :D

A power-on delay doesn't cause any problems, but I don't think it's really needed either.

Best regards,

Mikkel C. Simonsen
 
There's no real consensus out there on cathode stripping. Everyone seems to agree that it's a real phenomenon for high power transmitter tubes, but there is disagreement about its effect on signal and audio output tubes. Some people (e.g. http://hometown.aol.com/kasman01/weyer.txt ) claim that the effect is more important on low-level preamp tubes than audio power tubes.

Without any convincing evidence either way, IMO it makes sense to be careful if you're going to be using expensive NOS tubes. If you're just using cheap modern tubes, it's probably less of a concern.
 
diyAudio Senior Member
Joined 2002
Hi,

What IS cathode stripping?

Before you even consider implementing a time delay in order to avoid this you should first look at what can cause it.

The answer is pretty simple: the only way it can be caused under normal conditions is by the user.

It doesn't really matter whether or not your amp/preamp/whatever uses SS rectumfriers or airless bottles: anyone can damage a tube by asking it to do something it either can't or isn't ready to do yet.
IOW let your gear warm up prior to use so it's ready to deliver the current that's being asked of it.
If the tubes' cathodes aren't sufficiently heated up then those cathodes can be stripped to the point that little emissive material remains rendering them utterly useless.

So, if you're careful with your gear you don't need this extra gizmo, after all it too can fail. Remember Murphy?
If you're a guitar player it can be useful in order to keep the amp warmed up...
I wonder how many players actually use that switch once on stage but what do I know.

Simply mute the preamp output while the amp is warming up and nothing can go wrong. Simple as that.

Cheers,;)
 
Frank

Thanks for your explanation of cathode stripping.

Not really trying to invent the wheel here but it makes sense to me to use this device to avoid the possibility of cathode stripping.

Quote:

It doesn't really matter whether or not your amp/preamp/whatever uses SS rectumfriers or airless bottles: anyone can damage a tube by asking it to do something it either can't or isn't ready to do yet.
IOW let your gear warm up prior to use so it's ready to deliver the current that's being asked of it.
If the tubes' cathodes aren't sufficiently heated up then those cathodes can be stripped to the point that little emissive material remains rendering them utterly useless.

By using the delay on turn on relay the voltage is delivered after the tube has warmed up.

As to the life span of this device. Being an industrial device it is rated in hundred of thousands of cycles and is virtually fool proof.
I have design control circuits for machines in the past that use repeat cycles and use this same family of controls with no problem. With a use rate of 4 times a day this device would still be running after 300 plus years. I think Murphy would be proud.
 
Well, something was gained by this post. SY found a new source
of relay tubes.

I learned that not only were prior comments in other posts about cathode stripping incorrect but the actual damage is done to tube by asking them to work before they are ready.

Kinda like forplay I guess... got to wait until the right time to apply the signal.

:bigeyes:
 
Ex-Moderator
Joined 2004
You want a nice soft start that gently ramps up the voltage over about 30 seconds? Put a damper diode in series with the HT filter, after the SS bridge. I use a 6D22S, which was cheap and readily available. I use the 6D22S in the negative line, so that its top cap, which is connected to the cathode, is not at a dangerously high voltage. There are other types of TV damper diode that don't use a TC.

I also bypass the 6D22S, after 40 seconds, with a delay circuit using a 555 chip driving a relay, because I'm a bit short of B+ and I don't want to lose the 15v drop across the 6D22S. (Once it's warmed up, it doesn't need to be in the circuit any more).
 
ray_moth


While your circuit and idea sound very good wouldn't it be easier to use a delay relay instead?

Frank

Let me explain why I was uncertain as to cathode stripping upon sudden turn on.

In the 2004 catalog from Antique Electronic Supply on page 19 there is a mention of a SS rectifier PN T-SSR01.
In the description of this device there is also a note: It states Quote: Because there is no warm up of a rectifier tube when using this solid state device, it is critical that a standby switch is used that will allow the power tube filaments to warm up and generate an electron "cloud" around the cathode before high voltage is applied. This will prevent "cathode stripping" in power tubes.

Are they incorrect in their notice?
 
diyAudio Senior Member
Joined 2002
Hi Joe,

Quote: Because there is no warm up of a rectifier tube when using this solid state device, it is critical that a standby switch is used that will allow the power tube filaments to warm up and generate an electron "cloud" around the cathode before high voltage is applied. This will prevent "cathode stripping" in power tubes.

When B+ is applied prior to Vf nothing can happen as there's no electron flow possible.
They are correct in so far that if the user doesn't wait long enough for the cathode to reach operational temperature, damage (cathode stripping) will occur IF the user is yanking the amp (guitar players, ya know...) too soon.
But that applies to the 5AR4 the SS rectifier is replacing just the same.
The only difference being that B+ and Vf/Vk kind of ramp up together, the rectifier has a heater too, you see....
I suppose they issued the warning because some guys thought that because they now had SS rectification they all of a sudden could use the amp straight away :whazzat: and returned damaged output tubes to the vendor claiming replacements under warranty or something along those lines.

IOW, just a vendor covering his rear end...Understandably so IMO.

Cheers, ;)
 
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