The Tektronix model 564  storage oscilloscope

by Ralph Klimek October 2012

The scope was found on top of a pile of scrap metal that was about to be sent to the masher. I made big sad eyes at it and the nice man who was loading up the pile of metal said just take it and run. So run I did, or rather lurch clumsily along back to the car that was parked about 500 meters away.  I think my arms are now 50cm longer than I remember them !

Why did I pick this unit up ?  I do not yet own an analog storage scope.  I do not know how the electron storage tube works, so what better excuse was there?  

It is a nice looking rack mount unit and despite the aluminium case and chassis is  very heavy.  The interior represents the best of the legendary skill and quality of Tektronix, which while superb in their own right, I think, still came runners up compared  with HP.  Your opinions may vary !
The unit is an interesting  solid state and electron valve  hybrid.  The mainframe is entirely solid state, whilst the plugin timebase and vertical amplifier units are electron vacuum tube units. The mainframe was designed to utilize the large variety of plugins from other Tektronix series scopes.  My vertical amplifier plugin  only has 1Mhz bandwidth which is a bit disappointing. Maybe the Gods o' Cargoe  will let me have the 5Mhz plugin one day !

The previous owners of the unit had thoughtfully cut off the power cord to prevent tinkerers like me from from getting zapped  and the flow-on legal hassles.  The unit had been stored in a clean dust free location, and even though it looked as if it had not been used for 30 years, the interior was remarkable free of vermin and dust. Tektronix believed in having ventilation holes at the top of their instruments, permitting dust, liquid and vermin entry. There was some evidence of dust ingress , but not enough to condemn this unit to landfill.   Befor powering on, to see if there was still signs of life, I did the following.   All valves were removed from their sockets and reseated. All transistors, which were also all socketed, were reseated.  All pots got a squirt of electrical solvent  and fully tweaked a couple of times, but off course, after marking their setting !  I have learned that quality components made in the sixties  generally do not deteriorate. Things were overengineered back then.  There was no reason to suppose that this unit would not work or leak smoke.  You would be suprprised to learn just how reliable electron vacuum tubes were, if run at their thermal specification. They are almost never to blame for equipment shortcomings, it will be something else.

I was not wrong.  It just worked.  One channel of the vertical amplifier has intermittant issues with the input attenuator switch, this being due to dust ingress from the top ventilation holes.  Even so, this is quite an achievement for equipment of this age.  The PCBs in the mainframe unit are dated  1967.  I was in school then, grade 2 just learning to read a bit. The plugins are even older  and would be late fifties vintage.  It is amazing that the storage tube still works as well as it does.
A captured trace remains clearly visible for over an hour.  Time to read the manual and learn how electrostatic storage tubes work.

The other thing I did, before powering on I checked the resistance of all resistors. After 50 years, composition resistors can drift high in value.  Nothing was out of specification.  They knew how to make reliable components back then,  a skill that would appear to be now lost.

The model 564  scope coming outside for a photo shoot.
The washing was out and it was not raining !
The old Tektronix logo actually was an oscilloscope tube ! I guess their engineers knew what to do after arriving at work !  (Beats a mission statement!)vertical amplifier plugin, sadly only 650Khz bandwidth on offer here
timebase plugintimebase plugin withdrawntimebase plugin. this is craftsmanship.
timebase plugin. omg!  theres' a transistor lurking  in there !timebase plugin  theres' a transistor in there !  Thatll never replace valves !timebase plugin
timebase pluginvertical amp withdrawnvertical amp plugin 
solid state begins to make its appearancevertical amp plugin vertical amp plugin 
vertical amp plugin vary-caps to set square wave response for each rangea bit of dust has contaminated the attenuator modulethe most magnificent tube.  The previous owners had written "discard". I wont.
mu metal tube sheild. Personally tested!the low capacitance transmission lines go to the deflection plates of the tubesolid state EHT supply
first hint of solid stateall solid state mainframe  made 1967all solid state mainframe but still all active devices in sockets, as if transistors were not quite to be trusted!
These are RTL gates. TTL had not been invented yet.These electrolytic caps do not bulge. They were correctly made back the warning. The ceramic tagstrips need special care.
deflection plugin, timebase range switchdeflection plugin  timebase capacitors.on ceramic tagstrips to minimise leakagelousy dust filled slide switches. was there nothing better in 1965 then these ?