[Henry] Are 3B28's reliable??

[Dave Harmon]

That's all a bunch of unsliced baloney. Don't use resistors or anything
else....
The 3B28 is a plug and play replacement for mercury vapor 866 rectifiers.
The 3B28 has Xenon gas which may or may not glow slightly depending on the
voltage and current.
The big deal here is the 3B28 has no warm up time.
If the 866 is not warmed up long enough the mercury will still be liquid and
cause a short from plate to cathode. 
Obviously, this isn't good. 

If the HV comes on before the mercury heats into a gas, you can always hope
the fuse or breaker blows quickly enough and the cathode winding will not
open and neither will the secondary of the HV transformer.
The HV secondary and the cathode secondary will be shorted together by the
liquid mercury.
Of course...this is not supposed to happen.

So.....the best thing to do is use the 3B28's and don’t be concerned.
You can get 3B28's from Frank Krize K5SVC. He has a store on the auction
place.
I've used him for years and always got the good stuff from him at fair
prices.

If your amp was designed for 866 or 3B28 rectifiers, it will not have a step
start feature to protect the sudden application of HV to the filter caps. 
If you solid state the rectifier(s) the diodes will likely be destroyed by
the sudden startup surge.
The filter caps are like a huge glass of water....as long as you fill them
gradually there will not be any problems....such as with a glass rectifier.
With SS diodes, that glass of water is filled instantly and the diodes will
likely be crowbarred.

An example is the 3K-A.
It was designed for SS rectifiers and has a manual step-start feature that
works.
I bought one new in 77' and it's still going strong today.....34 years
later.
A true California Kilowatt.
Dan will confirm everything above.
73

Best

Dave Harmon
K6XYZ[at]sbcglobal[dot]net
Sperry, Ok.


-----Original Message-----
From: henry-bounces at mailman.qth.net [mailto:henry-bounces at mailman.qth.net]
On Behalf Of Milton Valerio
Sent: Monday, February 07, 2011 3:05 PM
To: henry at mailman.qth.net
Subject: Re: [Henry] Are 3B28's reliable??

Yes that was another option but I have heard several encountered opinions
regarding that, ones says that is just as simple as plug and play others
says not, one need to put a resistor somewhere because resistance are
differents etc so I'm affraid to make a mistake here but hey I feeled
tempted to do it, yes on ebay you see them from time to time.
 

--- On Mon, 2/7/11, Tim Kass <k8wbl at yahoo.com> wrote:

From: Tim Kass <k8wbl at yahoo.com>
Subject: Re: [Henry] Are 3B28's  reliable??
To: henry at mailman.qth.net, "Milton Valerio" <oligo_cr at yahoo.com>
Date: Monday, February 7, 2011, 12:10 PM

I suppose they are also subject to be "gassy".  I have replaced my 866
Mercury Vapor tubes with the 3B28 rectifiers...I believe that they may have
a higher flash point, can take a bit more HV and current.  You also don't
have to wait for them to warm up ... good luck...they do make solid state
plug-in as well.  Surplus sales of Nebraska has them but are expensive
through them...try Ebay..
 
73, Tim K8WBL

--- On Mon, 2/7/11, Milton Valerio <oligo_cr at yahoo.com> wrote:


From: Milton Valerio <oligo_cr at yahoo.com>
Subject: [Henry] Are 3B28's reliable??
To: henry at mailman.qth.net
Date: Monday, February 7, 2011, 12:01 PM


Hi to all, after having some problems with my 2K I though about how reliable
were NOS 3B28's?
I got a new pair of these but after put them in service I noted that the
purple color was not the same for both and also one use to show like
internal "lightnings" I always believed that NOS are bullet proof but is
that true or its a matter or luck.

Milton


      
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