EQUIPMENT BACKGROUND
After years of use and then storage once the analog Teletext television system was turned off yonks ago, I have finally gotten around to placing this professional, very well built equipment onto the workshop bench ... the "operation" has begun
This equipment was fully functioning but of no possible further use in our digital television (with no teletext broadcasts) era so now I have extracted components and modules "of interest" which can be used to restore another EH-1000 or possibly suit use in other "dated" equipment - parts that you will probably never find anywhere else!
Now it's time to take out the scalpel and start the op!
One the of the first things to note is that although this is branded Unaohm and manufactured in Italy, the components inside have been substantially sourced from European and English component manufacturers, the likes of Siemens and Philips.
THE DONOR EQUIPMENT
UNAOHM - Teletext Video RF Analyser
Model: EH-1000
Designed & manufactured in Milano, ITALY
Circa Late 1980's (based on advertisements placed in Wireless World at the time and the date stamp on the AC transformer core)
Technology: Analog video broadcast signal analysis - specifically for examining lines of Teletext information "riding along" with the video signal
Luggable (heavy at 15kg) due to the heavy duty Aluminium outer case but more importantly, the inside welded steel frame chassis inside.
Well engineered inside, logically laid out using a number of modules which are well interconnected.
Designed for 220V 50Hz operation (because of this, we used this equipment via an AC variac many years ago)
Green emitting rectangular CRT based front panel display
Interested in the technical nitty gritty? Here is an old copy of the spec sheet
Enough information about the "patient" now to the component(s) I have removed
RF ATTENUATOR
Rotary operation (300 degrees)
75 Ohm design impedance
Country of manufacture is unknown but strongly suspected to be in Europe - this attenuator looks very similar to Philips attenuators I have previously removed from their RF test equipment.
Take a look HERE and judge for yourself
Part number: unknown - examined the component very closely and I cannot see any identification marks at all
This attenuator sits directly behind the front panel, right hand side.
This is a variable resistive element, rotary control over 300 degrees, designed to perform at frequencies up to approximately 800Mhz maximum (the highest frequency analog television channel frequencies)
A precision component, all metal with the main body/thread of the attenuator being Silver plated. It is entirely sealed, looks to have been "sweat soldered" in final assembly.
As it's original purpose was for use with television RF frequencies, the design impedance is 75 Ohm
The "input port" is a Belling Lee male connector (often just called a PAL RF connector) which can be unscrewed although this still leaves the centre pin in position and I couldn't budge that pin at all - it is fixed to the main body.
The "output port" is presumably soldered to the rigid copper coax which has a Chrome cover hiding the actual connection. I cannot look further at this connection because of the rigid coax, to bend the coax would change the shape of the coax and perhaps make the component not suitable for use in it's original equipment. The "other end" of the rigid coax is bare and with a solid Brass threaded cover - this thread matches that of a BNC panel connector.
DIMENSIONS:
Total length of the component: 100mm
Total width of the component (includes the side port and rigid coax) 70mm
Main body: 36mm diameter x 22mm deep
Control shaft: 24mm length (Brass) x 1/4" diameter ROUND (you need a collet knob on this shaft, no flat spot)
WEIGHT: 100g
TESTING:
For years this equipment was working just great but it has been idle for quite some time so I have made a basic DC resistance test after I removed it from the equipment.
DC resistance varies from 77.0 Ohm ~ 40 Ohm
No idea what the power rating may be but we are talking LOW POWER attenuation here, for low level RF signals only.
Operation of the rotary control is smooth and from the "feel" of the component while being rotated, I would say this is a wirewound based variable resistor.
COSMETIC CONDITION:
USED
CLEAN
The main body is definitely Silver plated, when originally removed it had that "nice" Yellow/Brown oxidisation all over it - I have since cleaned it up when I was looking for identification marks. Now it is a nice, bright shiny "thing"
I am also supplying the original EH-1000 U shaped mounting bracket with screws, just in case they come in handy for the new owner.
