HARTLEY MODEL 13A
osciloscope was intended for the military and is therefor filled with "CV"
numbered valves, although the two fitted 6SN7GT's are presumably a replacement.
The 'scope is also tropicalised, which probably explains why the transformers
and chokes are sealed items. It seems that a quantity of these were sold
off as surplus throughout the 1960's.
It was probably intended for simple monitoring tasks as the vertical amp(s?) have no calibration markings on the control switches, unless you count the dial labeled ÷1, ÷2, etc. However the vertical sensitivity is of the order of 33mV/cm.
It is difficult to be specific about the bandwidth of the 'scope due to its flexibility. For example, the two Y amps can be switched in series to drive the Y1 channel for extra gain but with it comes reduced bandwidth. But the gain can also be reduced, upping the bandwidth. The manual claims that you can resolve around 10MHz maximimum.
British oscilloscopes of the period were seldom sold on performance. More likely sold by weight ! Nice light aluminium chassis and case, just a few valves, a light sprinkling of resistors and capacitors ... and four thumping great oil filled transformers and chokes. The manual states the unit weighs 75Lb but it feels much lighter than the similar-weight Cossor 1049.
A large number of these scopes appeared on the army surplus market throughout the 1960's. It was already popular in 1961 since it was featured on the front cover of the May 1961 Practical Television magazine. They were also still being sold in 1969, the advert below being taken from the May 1969 edition of Practical Wireless magazine.
|SERVICE DATA||Many thanks to Frank Adams for supplying a photocopy of the instructions / service manual. You can download a .PDF version from the Service Data page.|
|CURRENT STATE||Tatty. Although stored somewhere slightly damp the case /
chassis is aluminium so no rust.
Was apparently working when originally stored so the main battle should hopefully be confined to a few caps and crud in the valve holders - the rubber wiring seems to have survived well.
The graticule is missing as is the protective clip-on front cover. There should also be a plug-in voltage probe (using another valve configured as a cathode follower) which would be clipped into the protective front cover (what I also don't have).
|WHERE FOUND||A donation, having been rescued from Paul Stenning's boss's barn after a long hibernation.|
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THE OSCILLOSCOPE GALLERY
2nd July 2002