Date: Wed, 29 Jan 2020 06:46:37 -0600
From: Rob Atkinson <ranchorobbo@gmail.com>
To: "amps@contesting.com" <amps@contesting.com>
Subject: [Amps] Econco Tube rebuilding
<Econco rebuilds external anode tubes of a certain size. They won't
<deal with anything below around 2500 or 3000 watts plate dissipation.
<Small tubes for ham like 8877s can't be rebuilt. You may not be
<missing much. What I've heard is that the rebuild jobs used in
<broadcast (nowadays tube FM rigs) don't last all that long, maybe a
<year. This is why the industry is going solid state. The cost and
<availability of tubes is forcing them. Fortunately for ham, tubes
<when cared for, last a long time and there are plenty of 3-500s etc.
<out there.
<73
<Rob
<K5UJ
## Econco indeed rebuilds 3CX-1200A7, D7, and Z7.
Its on their list.
https://www.cpii.com/docs/related/23/Tube%20Ratings%20Data%20for%20Devices%20Rebuilt%20by%20ECONCO.pdf
## The above list is under section 4 of this master list of topics.
https://www.cpii.com/library.cfm/11#23 All rebuildable tubes appear to
be directly heated types.... no 8877 etc.
## Talking to broadcast engineer friends, Econco rebuilt metal tubes
are very good quality. 4 years in 24/7 broadcast use. > 35,000 hrs.
Provided the cathode voltage is maintained
correctly. They run the fil V way on the low side... then fil V is
brought up .1 V after XXX hrs..to restore emission. They will also
use a Sola constant V xfmr, or similar, to
maintain constant regulated fil V.
## A ham buddy of mine deals with Econco several times a year. The
rebuilt tubes run like a top. I did also hear from broadcast
engineers who complained about NEW Eimac tubes
that crapped out within days. They were sent to Econco for a
rebuild... then ran flawlessly in the FM PA...go figure.
## SS broadcast pa Txs require almost nothing for maintenance....
changing out air filters. Typ setup consists of 10 x 1 kw
modules..and a mess of combiners. If one module craps out,
the remaining 9 x modules take up the slack. The mating switching power
supplies are the same deal. And both can be hot switched.... by the
janitor. Switching supplies operate at > .99
power factor..which is superb. KVA from street to RF power is typ >
92%. Superb, and tube TX cant match that... 72% is typ for tubes
operating in Class C for FM GG Triode broadcast.
## A lot of the real old 50s, 60s, 70s FM + AM tube txs are long
in the tooth. Parts are getting harder find in some cases. Like
trying to maintain a mid 60s car.. that is driven 24 / 7 /365.
Too much...down time = lost $$.
Gets to the point its more cost effective to just replace it with a new
SS unit. Initial install.... then lock the door behind you. Some of
the tube Txs consisted of 2 x TXs..and a combiner. If one
crapped out, you still had the 2nd unit.... and are down only 3db.
## Here in BC, AM broadcast Tx are mostly off the air.... replaced
by a spot on the FM band. And the spanky new FM tx will be....SS.
## I have seen Econcos rebuilt tubes, they are good quality. Econco
can now also rebuild chinese and also Svertlana tubes.....per the
Email I got from them a while back... few months.
Jim VE7RF
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