[Heath] FW: Results of experiment with reactivation of 572Bs in SB-200

[Jerry Haigwood]

-----Original Message-----
From: Jerry Haigwood [mailto:jerry at w5jh.net] 
Sent: Wednesday, August 08, 2012 8:42 PM
To: 'kgordon2006 at frontier.com'
Subject: RE: [Heath] Results of experiment with reactivation of 572Bs in
SB-200



-----Original Message-----
From: Kenneth G. Gordon [mailto:kgordon2006 at frontier.com]
Sent: Wednesday, August 08, 2012 7:36 PM
To: Jerry Haigwood
Subject: Re: [Heath] Results of experiment with reactivation of 572Bs in
SB-200

...
>  I am currently running a pair of RF Parts labeled Chinese made tubes 
> which I suspect are actually Shuguang made.  So, you are telling me my 
> Chinese made Shuguang, re-labled RF Parts tubes "are very marginal 
> even when new."

>>Yes. At least in my SB-200 they have proven to be very marginal. What amp
are you running yours in? When did you >>install them?

SB-200 like yours.

> Well, my tubes are performing well and have been performing well for 
> about 6 months now.

>>Come back to me in another 3 to 6 months and tell me they are still
working as well as when you put them in. As I >>said, mine worked very
well....for up to 9 months...after that their emission, grid current, and
plate current >>dropped off.

I'll be glad to do that!

...

>>I don't worry so much about power out of the exciter as I do about
amplifier grid current: even so, my exciters are >>outputing around 50 watts
or less.

>  To see peak power you need a peak detecting wattmeter.

>>Which I have: a Heathkit HM-2140, a peak-reading wattmeter, which I have
calibrated myself.

>  Very few
> wattmeters are actually peak detecting.  I currently use a Telepost 
> LP-100A Digital Vector Wattmeter.  A single dot from your keyer will 
> show you the peak power output from your amplifier.  If you can't see 
> peak power output with only a single dot from your keyer, you do not 
> have a peak reading wattmeter!

>>That's correct: so?

Well the problem is that most meters that claim to be peak reading are NOT!

>  I worked for a tube manufacturer for 5 years as an engineer.
> All tubes require aging to activate the cathode and to burn off 
> impurities such as oxygen.

>>Yes. So?

>  Your re-aging schedule for these 572B tubes is highly suspect.

>>I am NOT "re-aging" them! Please re-read my post on reactivation.

Sorry to inform you Ken.  But, re-aging is a term meaning reactivation!

>  Since we don't know how the manufacturer made the tubes or his 
> process for aging, it hard to determine any type of re-aging schedule 
> for them.

>>I am NOT "re-aging" them.

Yes you are!!!!!

>  We should never apply a "generic" re-aging schedule designed for 
> 304ths

>>304TLs....and Cetron 572Bs too...

Why not add every other tube to that collection?  It would make as much
since.

> or such to any modern day manufactured tube.  It is like using 1930 
> repair techniques on a modern day microprocessor controlled radio.

Uh-huh....

I do not get this comment.  Ken I hope I can disagree with you with out you
resorting to personal criticisms. I am disagreeing and telling you why I
disagree.  Uh-huh...

>  It just
> doesn't work!  Since you have said, "I doubt if I will ever buy 
> another Chinese-made so- called '572B'," I am guessing you will be 
> buying Russian built Svetlana 572Bs

>>No. Svetlana hasn't made new ones for at least the last 5 years, and I
don't expect them to start doing it now.

> and adjusting the bias correctly or converting all of your amps to 
> something else (I am not even sure Svetlana makes 572Bs anymore).

>>No. They don't.

>  There are no US manufacturers of 572Bs and I doubt if anyone is going 
> to start up making them soon (perhaps they could make 572Bs and buggy 
> whips at the same time?).

>>Sure: why not. You would use some in your amp.

Err..., I am not sure the buggy whips would fit. ;-)

My comments are:  I doubt if we will see any new tubes from the USA.  It is
time we educate the Chinese on what we need.  Let's quit being so critical
and encourage them to do a better job for us.  It is the only game in town.
We need to see if we can improve it.

>  BTW, you will find 4CX250B tubes very hard to cool.

>>No more difficult than any other external anode tube.

Yes they are, much harder than other external anode tubes.  The cooler on
the 4CX250B is a very tight, dense cooler.  Tubes such as the 8930, 8874,
8875, etc. are much easier to cool.  The back pressure is much lower than
the 4CX250B.  The 4CX250B was made very compact for the military in order to
be used in cavity designs, etc.  The 8930 would make a much, much better
tube for you.  It is just harder to find.  It is just a 4CX250B with a
larger anode cooler which gives it lower back pressure.  It performs the
same or better.  BTW, I am a fan of the 4CX250.  I have built several VHF
amps using the 4CX250B.  Here is a link to one of my designs.

http://195.84.101.101/~goranl/projects/pa2x_4cx250b/2m_pa_4cx250.pdf
Please note my call used to be KY4Z.  The person here LA0BY gives me credit
for the original design.  It is really not all my design.  I just stole
pieces here and there from other people and then wrote what I had done. This
amplifier is capable of putting out >1200W on the 2 meter band.  It was my
EME amp for several years.  I used it to work Owen Garrett in the Space
Shuttle - a real thrill for me.  If you will take the time to look at the
blower and Teflon chimneys, you will see the cooling methods employed by
EMEers.  I ran my 4CX250B amp on EME for more than 2 years of hard use
(abuse?) and never ever changed the tubes.  There are two tricks to using
the 4CX250Bs.  1) no more than 1mA grid current!  2) push lots of air past
the tube.

>  You need to figure out how to move 6.4CFM of air at .82 inch of water 
> back pressure.

>>Yes. I have that covered.

That is good!

>  It is hard to find a blower to meet those requirements.
> Dayton makes good blowers but their blowers will not fit onto the
> SB-200 very well.  It would be best to mount the 4CX250Bs in a 
> sub-chassis in the
> SB-200 and remote mount the blower under the desk or wherever.  A 
> better method for cooling 4CX250Bs is to pressurize the top of the 
> chassis and use a Teflon chimney which fits tightly around the tube 
> plate and fits tightly against the top of the chassis.  Holes for the 
> air to escape can be drilled at the top of the chassis directly above 
> the Teflon chimney.  The air can then escape through the anode cooler, 
> up the Teflon chimney, and out of the holes.  Small holes can be 
> drilled into the bottom of the sub-chassis to allow some air to escape 
> out of the bottom past the tube pins providing cooling for the pin
connections.  Good luck with your conversion.

See the above link for a picture of the Teflon chimneys and cooling method.

>>Thanks. 

>>vy 73,

>>Ken W7EKB

Jerry W5JH