[Top] [All Lists]

Re: [Amps] 1993 Vintage 3-500z

To: "Chris Hays" <>, <>
Subject: Re: [Amps] 1993 Vintage 3-500z
From: "Carl" <>
Date: Tue, 6 Jun 2017 13:17:22 -0400
List-post: <>
That process will do nothing for the 3-500 family.

Since the ongoing gettering process requires anodes to be run at color at least 3-4 times a year from new and a lot more when they have sat for years an entirely different process is needed. Running filaments only does nothing but waste 75W per tube. Indirect heated cathode tubes respond well to filaments only.

In older amps such as the SB-220, Drake L4B, aHunter 2000C, and others with the pre 1500W OUTPUT FCC rule compliance CW/SSB switch it is often possible to run them at color at the lower HV position which is just above the threshold of creating an internal plasma arc. Running as an AM linear, out of tune on 80/160, shorting the bias diode when used, can all create that nice red/orange glow.

If the tube arcs at that voltage then a method to bring the HV below 1200V and positive biasing the tube MAY work but it will also likely take lots of hours. Just as a test Ive had a few take up to 2 days in the basement during winter so the electricity use wast wasted.

A regettered tube will require less time before it needs it again if it was a real dog to start with. I use a pair in a 60's Hunter 2000C regularly as an AM linear in the SSB position so they get a bright orange and that has kept them happy for about 3 years sofar. My bought new in 1986 LK-500ZC wih the original Eimacs has been beat on hard in contests, pileups and on AM and hasnt burped yet.and will still do an easy 1200W.

The only ceramic-metal tube Im aware of that had actual seal leakage is the 4CX300A and that caused the USAF and others a lot of grief and money.


----- Original Message ----- From: "Chris Hays" <>
To: <>
Sent: Tuesday, June 06, 2017 12:39 PM
Subject: [Amps] 1993 Vintage 3-500z

Not necessarily, but you need to bring them up carefully.

If you have or can get access to a hi-pot tester, that might be the best
first step.

However, if it were mine:

1. Remove one of the tubes so you aren't trying to deal with two at a time.

2. Run filaments only for 3 to 4 hours.

3. Bring plate voltage up slowly (you will need to get a variac connected to
the HV primary so filaments will stay hot. Also, you should put a non-slow
fuse in series in case it decides to flash over.

4.  When you get to a kilovolt or so, carefully apply some drive gradually
bringing it up (obviously you need a dummy load here that can take the power
for a period of time)

5. Bring up drive watching plate current carefully.

6. If it arcs, back down and repeat.  One thing I have learned is that if
the tube arcs without destroying the grid or filament, the arc will have the effect of cleaning some of the gas out of the tube (I know this doesn't make
sense, but years of bringing up really big tubes that were gassy has
confirmed this). The fuse is very important here to prevent damage to the
tube and the power supply.

6a. If it continues to flash over after a few tries, you might want to
consider that tube a lost cause.

5. Once you get drive to where the tube is saturating (as in more drive does not yield more output) leave it there for a time. If the plates glow all the

6. Start slowly raising the high voltage a bit at a time, adjusting drive
until you are at where the tube is at rated output (remember this is one of
two, so it will be half the normal output of the amp).

7. If you get to the point where you can get the plates reddish, leave it
there for an hour or so.

8. Repeat for the second tube.

Your mileage may vary.  I'm sure others will comment and may have more
elegant methods.  If you aren't comfortable doing this I suggest getting
some help.  Remember, high voltage kills!! Be careful!!

Chris, AB6QK


Message: 1
Date: Tue, 6 Jun 2017 10:20:47 -0500
From: Joe <>
To: Catherine James <>, Amps group
<>, Kimberly Elmore <>
Subject: Re: [Amps] 3-500Z cool down time
Message-ID: <>
Content-Type: text/plain; charset=utf-8; format=flowed

So this SB-220, that has been sitting since 1993, the tubes are most likely

The Original Rolling Ball Clock
Idle Tyme
On 6/6/2017 10:14 AM, Catherine James wrote:

It's generally recognized that glass tubes have poor shelf life due to
slow leakage.  I have heard many reports of this from people I trust.

    They will last much longer if the plate gets hot at least a few times
a year so that any leakage can be gettered away.  For tubes in regular use
rather than on the shelf, it doesn't seem to be a problem, but it makes it
difficult to stock up with spares.  Many amateur users rotate their shelf
stock into the amp at least once a year.

Is the 3-500Z used much outside of ham radio today? If so, who are the
primary users?


Amps mailing list

This email has been checked for viruses by AVG.

Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>