The Z Core is an easily-installed adapter that allows almost any vintage oscilloscope or CRT based display device to safely accept digital blanking pulses from a microcontroller or other low voltage source.
For information on why this is so cool, watch out for a post – coming soon!
Cautionary Disclaimer
It is a condition of purchase and use of this unit that you read and understand the below warnings.
This assembly operates at HIGH VOLTAGES, and at LETHAL currents. High voltages may be present even where not indicated. Do not touch components inside this assembly, even after removing power. This assembly is not user-serviceable.
This assembly may incorporate original vintage electronic circuitry and components. While every effort has been made to reduce risk of circuit failure, Oscilloclock.com bears no responsibility for any accidents, fire, injury, or death. Do not leave this product operating while unattended.
Do NOT allow children, pets, or unsuspecting adults near this assembly without strict supervision.
For warranty terms, conditions, and other disclaimers, please refer to the Invoice.
What you get
This Oscilloclock Z Core assembly consists of a lovingly hand-crafted Oscilloclock circuit board (or two) mounted on attractive cast acrylic – ready for installing into your chosen CRT display device or an external case of your own design.
Boards are sprayed with protective high voltage lacquer and the assembly is then fully tested. The set includes high voltage and high temperature tolerant harnesses, a power pack (if you require it), technical documentation, and a 2-week limited satisfaction guarantee.
Features and specs
The Z Core is a high-voltage, isolated, medium bandwidth digital DC amplifier.
- Power supply: 7.5-10V DC 1.2A (peak)
- Input: 3.3-6V DC digital, TTL/CMOS compatible, floating, 15mA@5V
- Output: Approx. 45V DC digital (negative-going)
- Input isolation: 150V DC continuous
- Output isolation: 2.2kV DC continuous
- Power control: 5V logic – pull low to shut down supply
The inverted output voltage (when applied on top of an existing negative bias) is sufficient to achieve grid cut-off in nearly all oscilloscope CRT circuits. Similarly, the output isolation voltage is sufficient to stand off typical cathode potentials.
When ordering a Z Core, please tell us your beloved CRT device’s manufacturer and model number. We may be able to confirm compatibility for you.
Installation
The Z Core effectively sits in series between your device’s blanking supply and the CRT grid. 1-2-3 and you’re done!
- Snip the wire connecting to CRT grid.
- Connect the orange wire from the Z Core to the circuit side of the cut wire.
- Connect the green/yellow wire to the CRT grid.
Unlike these tongue-in-cheek photos, be sure to solder your connections, and use electrical tape to insulate any spliced wires. And don’t touch anything when your scope’s power is on! These connections, and most of the Z Core assembly itself, float at up to 2kV potential with respect to the chassis.
Shocks will be nasty, and very possibly fatal.
Alternative configurations
The Z Core can alternatively be configured to generate a positive-going output to insert into the cathode circuit, rather than directly to the grid. However this modification requires case-by-case analysis. Changing the cathode potential with respect to all other electrodes, even during a blanking interval, may have side effects that are evident when the beam is unbanked again.
The Z Core can even be configured to directly drive deflection blanking plates, for the rarer CRTs that feature these fascinating electrodes!
Reach out for special guidance if you feel these configurations may be best for you.
Other connections
If you’ve already connected the Z Core to your CRT device, make sure the device is OFF (and ideally unplugged, to be safe!) before making these connections.
- BLANK connector: Connect the white wire to your controller’s blanking output, and the black wire to blanking ground. Note that a positive voltage will unblank the beam.
- PWR IN connector: Connect the red (+) and black (-) wires to a DC 9V power source. (Or, plug in the AC adapter if one has been supplied with your unit.)
- (optional) CTL connector: If your controller has an output to turn the Z Core on and off, connect the purple wire to that output, and the black wire to controller ground. Note that pulling this line low will shut the Power Board off.
Warning: unless the CTL line is held low, the Z Core will turn on as soon as power is connected. Avoid touching the unit as the 45V output voltage may give you a slight shock. And of course – never, never touch anything when the host oscilloscope is powered up! You will have more than a shock.
Connecting up the Z Core 2 Ex
The Z Core 2 Ex is a version of the Z Core 2 that has an off-board, external blanking amplifier.
- CRT GRID IN connector: Using the supplied harness, connect this to the EXT BLANK connector on the main Power Board.
- BLANK OUT connector: Connect the harness with orange and green/yellow wires. This are connected into the CRT grid circuit as described previously.
Mounting and Clearance
Your Z Core ships mounted on attractive cast acrylic, with nylon spacers and polycarbonate screws, washers, and nuts.
This is because the Z Core board(s) float at up to 2kV potential and needs to be sufficiently isolated from its surroundings.
When choosing a mount location in your chosen device, be sure you can maintain at least 5cm clearance in all directions, to prevent arcs and flashover.
And always, always use nylon or plastic spacers – never metal! Feel free to re-use the components shipped with your kit.
EMI and wire lengths
There are three components of the Z Core that emit relatively strong electromagnetic radiation:
- The transformer mounted on the Power Board.
- The blanking amplifier section at bottom right of the Power Board (or, in a Z Core 2 Ex, the separate CRT Board).
- The green/yellow and orange wires connecting to the grid circuit, which can act as antennae.
The transformer emits approx. 200kHz radiation, and harmonics may extend into the MHz range.
The blanking amplifier and the grid wires will emit radiation at the pulse frequency, with harmonics extending into the MHz range due to sharp rise/fall times.
To minimise interference from these sources,
- Mount the Power Board away from your device’s sensitive horizontal and vertical deflection amplifiers.
- Keep the grid circuit wire lengths short. (If you have a Z Core Ex, mount the CRT Board close to the end of the CRT.)
Note that this will rarely be a serious problem! Even in the case of the extremely compact Kikusui 537, it was easy to find a good mounting location and there was negligible interference.
Thermal considerations
The Z Core will automatically shut down if onboard temperatures rise past a certain threshold. Fortunately, the Z Core itself emits only a small amount of heat, which is unlikely to cause issues.
Do not mount the board directly above any tubes (valves) unless there is substantial ventilation – this can quickly push temperatures to excess.
Performance characteristics
The Z Core’s bandwidth and pulse handling characteristics will be satisfactory for most controller applications. In fact, the characteristics of the CRT itself may be a limiting factor, depending on the CRT.
Measuring conditions:
- Input signal: 5V 100kHz square wave,9ns rise time, 13ns fall time
- Load: 20pF via 200mm 22AWG harness
| Measurement | Assembly: Z Core 2 Ex |
|---|---|
| Base voltage | -46V |
| Rise time | 130 ±10 ns |
| Fall time | 180 ±10 ns |
| Propagation delay | 120 ±10 ns |
| Effective bandwidth | DC to 3 MHz (limited by rise/fall time) |
Note that the Z Core 2 Ex is an early configuration of the Z Core assembly, intended to put some new-old-stock boards to good use. Later Z Core configurations are far more performant, and specs will be updated here as they ship.
Q&A
Q. My Z Core has a nice red light (FAIN FAIL) that turns on after several seconds of operation. Is it going on to blow up?
No. You are simply the lucky owner of an over-populated Power Board. That is, your Power Board has been fitted with more optional features than a Z Core requires, including in this case an onboard fan controller.
The Z Core dissipates only around 1W of heat and does not need a fan to keep cool, but the controller is detecting its absence. Ignore and enjoy the lighting effects!
Q. What happens if I shut down the Z Core (or unplug it)?
When shut down, the Z Core output is effectively a low-impedance shunt. This means that you can use the oscilloscope almost exactly as before!
Almost: the harness and the powered-off Z Core components introduce additional impedance into the grid circuit, so the scope’s blanking pulse shape may be affected very slightly.
Q. What if I get the grid connections reversed?
Don’t do it!
The grid acts as a brake and needs to be negative with respect to the cathode. Reversing the wires would cause the Z Core to force the grid positive, which would attract electrons rather than repel them!
There would be massive current drain, the cathode circuit would overheat, the Z Core would cry out in pain, the phosphor would burn, and generally it would be a calamity.
Wait, that sounds fun!
But let Oscilloclock Labs try it first and give you the write-up.
Q. Will the propagation delay, rise time, fall time characteristics impact my visuals?
They might. Let’s look at propagation delay first. Say your controller is drawing a vector line between two points. Say it is designed to be blank the beam at the exact same instant that it begins deflecting from the start point.
If the propagation delay of the X and Y deflection amplifiers don’t match the propagation delay of the Z Core, the beam may unblank partway through the line! Or it may unblank prior to the start point, showing something it shouldn’t!
For this reason some controllers, like the Oscilloclock Bare and Oscilloclock Connect, feature a variable delay between the X/Y and the Z outputs. This offsets any imbalance in propagation delay.
Q. What is the BIAS control for?
Z Core 2 owners will find a BIAS control on either the Power Board or the external CRT Board. This is pre-adjusted in the lab prior to shipping, and should not require adjustment. In fact, don’t even try, as the control is at 2kV potential when your scope’s power is on. Danger!
However we all love to tweak things, and no doubt your curiosity got the better of you. You messed around with it, didn’t you? If you need to get this back to where it was, follow these steps.
- Set up a partly blanked figure on screen, using your controller or some signal generators.
- Using an insulated screwdriver (repeat: insulated!!), turn the BIAS control to its maximum clockwise position.
- You should see that the trace is being excessively blanked. That is, one end of your line (or arc) is being blanked out when it should be visible.
- Adjust the BIAS control in the opposite direction. The part of the trace that should be visible should start to reappear (start to be unblanked). Turn until just before the point where it does not unblank any further.
Q. Can I power the Z Core off my scope’s internal power supply?
Possibly! If your scope has a power supply with the right output voltage, and it’s not already maxed out, by all means hook the Z Core to it.
Note that the blanking input is floating, so even if your controller ground is not the same as the scope’s supply ground, it should work.
One warning: do NOT be tempted to rectify your CRT’s heater supply and use it to power the assembly! The heater is at cathode potential (2kV) and the Z Core is not designed to isolate inputs to this level.
Q. Can I measure the Z Core’s output with a multimeter or oscilloscope?
Yes! But only if you turn the connected device’s power off!
Remember that when your device’s power is on, these connections and much of the Z Core is at a 2kV potential. Without special HV probes, normal multimeters and oscilloscopes will NOT stand off this high potential to earth, and something will give. Or somebody. And that means you.
Q. My Z Core 2 gets a little warm…
Yes! You are the proud owner of a partially-populated Power Board rev2.x, which was designed to power up an entire Oscilloclock.
The Z Core feature by itself only eats a tiny amount of that vast lake of energy, and to ensure sufficient voltage regulation, we have mounted a resistive dummy load onto your board. This generates about 1W of heat which will, over time, make your board nice and toasty. But never HOT hot.
The board is designed for long-term operation at an ambient temperature of up to about 65 degrees Celsius. As long as you have left sufficient clearance around the board, it will not exceed this.
Just don’t mount it directly on top of a whole array of valves (tubes) – that might push it over the edge!
Q. My Z Core’s OVER TEMP light has turned on and it shut itself off. Why?
Your Z Core has a thermal protection circuit. This will automatically shut the device down if the on-board temperature exceeds a certain threshold for a period of time. After a period of cooling, it will automatically start up again.
While the Z Core itself only emits a bit more than 1W of heat, it might not be able to dissipate that in certain mounting arrangements. Check there is some degree of ventilation or heat transfer, where the board is mounted.
Needless to say: Don’t mount the board directly above any tubes (valves)!