Inrush protector - Yes or No?

[WW5AA]

Well I'm always willing to learn. It is just that I can not beleive that the makers of high end power supplies, X-Ray equipment using RF tubes, and amp manufactures are taking me to the cleaners by using inrush current protection. Maybe I should just stop reading the stuff on electrical engineering by IEEE.

73 de Lindy

[W3LK]

<< My AL80A has in rush protection in it from the factory.  >>

I was not aware that the 80A had factory installed inrush protection. It is my understanding that this started with the 80B, and not from the start of production, at that.

Again, the question I am asking is about protection specifically for the 3-500, not other tubes.

As for Ameritron's verbage, there is no mention of it in the 80A manual nor any mention of the requirement for such protection. What changed for them to issue such dire information? Further research? Large number of tube failures?

73,

Lon - W3LK
Naugatuck, Connecticut

[WW5AA]

Lon,

The paper work I have from Eimac with the 3-500ZG that I bought years ago for my Henry warns against inrush currents of more than 2X. I have seen articles in the past that have mention inrush currents in some amps as high as 10X. The manufactures of X-ray equipment (using 3-500Z) all have warnings about using inrush protection. Your right, Tom (W8JI) could set us all straight. In the mean time I will continue to use my MFJ ICP-120 inrush protection on my other amp. I wonder...did MFJ also con me?

[W3LK]

Lindy:

Perhaps hype was the wrong choice of words, but I reiterate, where's the dire warning in my 80A manual, or in my 30L-1 manual for that matter? There's no mention in the manual for the AL-811 or 811H, either. Perhaps 811s are immune to the problem.

I am NOT taking a position either way, although I know some of my remarks might be taken that way. All I want is a definitive answer to the question ...

Do I need an external inrush protector on my 80A. I don't give two hoots about any other amp.

To throw another question in, why do I only get the "thud" about a third of the time? I have kept track this past week and there's no set pattern for it to happen.

Thank you to everyone who have contributed to my confusion. <g> I really DO appreciate every one of your responses. Now if W8Ji would just join the discussion ...

73,

Lon - W3LK
Naugatuck, Connecticut

[WA0LYK]

The "hype" is probably part of the problem.  Just like with my 30l-1, would a failed power switch after 50+ years be considered a "problem"?  Most definitely not!

Your 80A may last 50 years if you do nothing, just like the 30l-1.  But, if using an inrush protector can extend the life of any of the components is it worth it?  Only you can answer that question for yourself.  I felt putting something in my 30l-1 was worth the time and money.

All most folks can tell you is that inrush protection is a cheap measure to take and will provide a measure of protection to all the components stressed by the current.  Whether that protection extends the mean time before failure of any given component is difficult to say.  If Collins had used a switch rated at 40 amps instead of 15 amps perhaps no one would have ever had a switch failure.  But, perhaps they would have.  Would the original power supply caps have lasted longer if the inrush current was only half what it actually is?  Who knows?  

As far as the thud being random.  Remember, the moment your switch makes contact you will be switching some voltage into the transformer.  That voltage is entirely dependent upon where in the 60 cycle waveform you make contact.  I expect that will be entirely random unless you use some kind of comparator to only switch when the voltage is some value, such as at the zero crossing point.  The fact that you hear a thud at times tells me you operated the power switch when the voltage was at or near its maximum.

Jim
WA0LYK

[N3OQD]

A friend recently upgraded the HV rectifiers and capacitors of an old Drake L-4B.  When he threw the switch, the plate transformer could not take the load of the fresh caps and it's secondary opened up.  If he had retrofitted a soft-start circuit, the tranny might still be functional today.  This was enough to prompt me to purchase the 120v Ameritron inrush protector for my AL-811 amp.  They also sell a 240v version.  Now, was this necessary for my application?  Maybe, maybe not.  One thing is for sure, it cannot hurt to add this kind of a device to an amp that does not have one in the first place.  

[W5DWH]

From what i have observed while repairing tube type radios, I don't believe that it is necessary.
1. Have you ever turned on a tube radio while watching the tubes? They come on slowly not in an instant like a lite bulb.
2. The purpose of the variac for troubleshooting is not  to "save" the filaments. It is to save the power transformer and rectifier tube from excessive loads.

In the antique radio restoration hobby, inrush protection is just something that some people think old radios need, kind of like safety caps.

I leave my stuff original. That's the way it was designed and it has worked that way for over 50 years, thus leave it alone.

73

W5DWH