[Amps] Tentec Titan 425 with GU74-B????

[DF3KV]

Hi Arne,

The Alpha amps were made in Bulgaria at the place which is today known as
ACOM.
All ACOM amps are supplied with GU74b.
I don´t remember what year (late 90)Mike Matthews from New Sensor (Electro
Harmonix) took over Svetlana factories for their audio tube production, but
I don´t believe that 4CX800 tubes have been produced at Svetlana (winged C)
ever.
I wonder if any transmitting tube is made at Svetlana St.Petersburg nowadays
anyway, I guess that factory equipment is now in China.
My guess is that Alpha relabelled  GU74b to 4CX800 and produced a data sheet
to give more confidence to US buyers.
Why would ACOM use old military tubes if new production is available and why
are they using now 4CX250B in their latest amp?

73
Peter 

________________________________________
From: N7KA at comcast.net [mailto:N7KA at comcast.net] 
Sent: Montag, 15. Februar 2010 22:17
To: DF3KV
Subject: Re: [Amps] Tentec Titan 425 with GU74-B????

Peter
 
What Carl says about a GU-74B may be correct.  However the ALPHA 99 which
was produced in Bulgaria had what was called 4CX800A tubes.  I have a DATA
SHEET from SVETLANA I got a few years back that is for a 4CX800A (dated
3/98).  Ask the owners of an ALPHA 91 or 91B what tube is in their amps and
most likely originals will be 4CX800A.  I do not have the 4CX800A in a file,
only a paper copy so can not send it to you..
 
Here is a reference of a USA supplier: 
http://www.rfparts.com/tubespecs.html   go down the list to 4CX800A and see
it has GU-74B shown also.
 
Guess its the old auto thing:  The English call it a bonnet, in the USA we
call it a hood.  You know, that metal thing that lifts up to expose the
motor of a front engined auto/car/ride.
 
The tube numbering system that is/was used by EIMAC:  here is a quote from
an EIMAC Catalog about the numbering system:  "EIMAC tube types are
identified by either a non-descriptibe sequentially-assigned 4-digit type
number, standardized and registered with the ELECTRONICS INDUSTRIES
ASSOCIATION (EIA), for non-duplicationthroughout the world, or by a coded
numbering system, designed to convey descriptive information about the
tube.  Many tube types can be identified with either number, and are
brancded with both.  
Take as example the ever so common work horse:  8877 also known as the
3CX1500A.  Branding would appear as 3CX1500A7/8877 where the 8877 is the EIA
Type Number.  Reference Page 5 of VARIAN (EIMAC) POWER GRID TUBE CATALOG
2267/101   10,000  4/92.  This 177 page catalog only cost $5.00 in 1992 and
I find it is worth its weight in gold.
 
But back to the 4CX800A.  See the May 1996 QST article written by George
Daughtrs (then AB6YL) that gave info to convert a DENTRON MLA2500 from 2ea
EIMAC 8875 to to a single SVETLANA 4CX800A.  Yes take ot a pair of triodes
and put ina tetrode by adding a screen and grid supply pljus some other
circuit changes. 
 
They even had a DATA SHEET for a 3CX800A7.  The SVETLANA catalog and many
data sheets show them using the 3CX****  or 4CX**** type number.
 
My TEN TEC TITAN 425 uses 2ea EIMAC 3CX800A7, my ALPHA 76A uses 3ea EIMAC
8873, and my ALPHA 77S uses 2ea EIMAC 3CX1500A7/8877.  Even have a new pair
of EIMAC 3CPX800A7 tubes on the shelf.  I like TRIODES.
 
Arne N7KA
 

----- "DF3KV" <df3kv at t-online.de> wrote: 
> 
> 
Hi Arne,
 
Svetlana does not make a 4CX800A7 and never did.
 
Please show me one

 
OK, in the past they produced GU74b
 
73
Peter
 
> 
________________________________________
From: N7KA at comcast.net [mailto:N7KA at comcast.net] 
> Sent: Montag, 15. Februar 2010 17:09
> To: DF3KV
> Subject: Re: [Amps] Tentec Titan 425 with GU74-B????
 
Peter
 
I am sure you have several replies.  SVETLANA makes 4CX800A7 (GU-74B). 
4CX800A7 is a standard nomenclature numbering system that defines a tube,
believe its IEA format.
 
Arne N7KA

> ----- "DF3KV" <df3kv at t-online.de> wrote: 
> > What is a 4CX800?
> > Was never made...
> > But it is true, tetrodes can not replace triodes without a major
redesign
> > 73
> > Peter