Oscilloscope Clock kit – was the design published anywhere?

[Chris56000]

Hi!

I've been trying to buy one of these Oscilloscope Clock kits for a month now and three sellers have all said they're "out of stock" – does anyone know where this design came from and is there any chance of still buying it anywhere?

What attracted it to me was the two board design with a large number of components to build – one of the boards is labelled "XYZ CRT control board v2.0" and there doesn't seem to be a label on the other one!

Chris Williams

[Wolfram]

That looks like it could be derived from the Cathodecorner SC2008 design: http://www.cathodecorner.com/sc200c.html

[ledtester]

About the kit... this unboxing/build/demo video was just put up yesterday:


#086 Oscilloscope Tube Clock Build 8SJ31J


Edit: I think the guy said he made 20 passes over of the trim pots to calibrate the display.

[Chris56000]

Hi!

That looks like it could be derived from the Cathodecorner SC2008 design: http://www.cathodecorner.com/sc200c.html

I agree it's probably the same circuit, but where am I supposed to get the power supply transformer from or details for making it?

I'm getting sick and fed up of people like the author of that site who post endless fancy photos but don't tell you where to buy the parts from or how to make an equivalent – I want a source of the parts, not endless stupid bloody photos and videos!

Every link and Oscilloscope clock project I can find online is either "sold out", "to be updated", (and David Forbes's site is dated "May 2008" with not a thing posted then) or "contact me", and the links are long dead – what's so secretive about these things?

Chris Williams

[tkamiya]

On that link, there is a PDF.  There is a circuit diagram.  There is a source code.  What more do you need?

Author was nice enough to give as much detail as he deemed suitable.  From there, it's up to you to come up with your own method.  Buying parts are not that difficult.  There are plenty of places to choose from as there is nothing unique about his design/construction.

Keep in mind, these people do this for hobby.  Once his stocks are depleted or lose interest, they just leave site just in case someone wants to see it.  There is no secret agenda.

[Chris56000]

Hi!

It's not the schematics, PCB or microcontroller code I'm bothered about as I found another repository of these late last night as well, but the pesky power supply transformer!

NOBODY has given any specification for it or any indication of where I can buy one!

On this thread:-

https://www.eevblog.com/forum/projects/etd34-size-transformer-for-a-scope-clock-design-tool-or-procedures/

. . .I quoted what I thought were the possible specifications for this transformer, but that was entirely "intelligent guesswork" on my part – all that was quoted for the transformer was "T1ST1A" – who made it? – core size and type? voltage outputs? – was it taken from another product the designer bought? – there's not a bit of information about it on the designer's page!

It uses an LM2586 "3A Simple Switcher" IC feeding a transformer with two high voltage secondaries and a 6.3V secondary for the CRT heaters on it, as well as the 5V/12V supply!

I don't want to start bunging bloody great 50Hz transformers in the thing as then there's weight and cost issues, plus the need for a mu–metal screen for the CRT to prevent the transformer field affecting the display – this is why I want details of how to make the S.M. transformer so it can be run off 12V from an adaptor plug, with no need to screen the CRT!

Chris Williams

PS!

I found another of these clock kits on eBay, allbeiit more expensive with an acrylic case kit included as well, which I ordered, and I'll wait and see if I get the usual "out of stock" nonsense – the listing said there were four available!

[tkamiya]

Hi!

Substitute and adapt!  (adopt?)  I don't know about TS1T1A but I wouldn't use such a complicated power supply for something like this.  For low voltage supplies, output voltages are obvious.  Just look at the 3 terminal regulators and add 3 volts.  High voltage supplies are only needed if you are going to use CRT tubes and drive it yourself.  If you are going to use oscilloscopes, they are not needed.

From top right, PWRGOOD is power good signal.  Pull it high.
POS250 appears to be (I don't know what this is...)
POS5GPS appears to be 5 volt for GPS
POS5A is 5 volt positive
NEG5 is 5 volt negative

Given whole thing is driven by 12V 1A, power supply capability is quite small.

GUN depends on your CRT if you are driving it yourself.  Take a look at tube's spec or if you are taking apart scope, look at its power supply.  Cathode will be 1000 volt to 2000 volt for cathode, something like 5V or 6.3V AC for heater, blanking is somewhere near 50 volts.  (see assembly instruction)  He used 1500 volt cathode.

Now, only question is POS250...  my brain is too foggy right now to go read a spec sheet.

Taking someone's project and turning it into yours always require some investigative work.  Luckily, this author did a good job of documenting.  I'm much sloppier than he is.

[Chris56000]

Hi!

The deflection amplifiers require a +250V h.t. power supply at about 25mA to drive the X and Y deflection plates of the cathode–ray tube, hence "POS250" – I'd mark it up as "HT+ 250V" as that is the UK terminology in use when I was learning valved and high–voltage circuitry!

The supply is obtained from a winding supplying about 125V r.m.s. using a half–wave voltage doubler, and the high–voltage CRT negative supply a ten–stage "cascade" arrangement.

Going back to the transformer, the LM2586 has a 3A peak switching current limitation, so a minimum amount of primary inductance is needed to prevent destruction of the device, and the point made about me being prepared to adapt the provided circuitry is quite valid, which I've no complaints over!

However, the designer should have stated as a minimum, the specific inductance A_L and the physical dimensions of the core he used, or an equivalent type – I'm quite happy with going through the design formulae to work out the rest of the details, turns ratios, wire gauge, etc.

The same point was raised regarding the ferrite pot core transformer used in the "EPE Electrolytic Capacitor Reformer" design in the Feb/Mar 2012 issue of EPE Magazine, this was a 26mm ferrite pot core listed by Jaycar Electronics in Australia that cost over £60 to send to the UK – I tried to order one, and there is no way I was going to spend over £60 in postage, import charges, duty, etc., etc., for this tiny item weighing 10 g at the most!

Not surprisingly, there were quite a number of fairly angry complaints raised on the UK Vintage Radio Forum about inadequate specification of important components, and not providing details of locally orderable/obtainable equivalents!

I have also purchased two of these cheap little 12V Chinese designed 12V d.c. – to – a.c. inverter modules, the claimed output being "110/220VAC at 150W", so given the Chinese penchant for vastly over–specifying the capabilities of their wondrous electronic creations, I would de–rate that three times, so taking the transformer size shown in the pic. as a rough guide, me thinks this is about the right size to handle the power for the SC200 design, and they're cheap and plentiful enough to dissect one of the transformers to get the number of turns, wire gauges, etc., from!

I propose to use the circuitry from this module as a base for a separate 12V operated h.t/e.h.t. supply circuit for non–PDA CRTs that can be built on a new small PCB and used for scope clocks, "octopus" component tester designs, curve tracer projects, learning about CRT operation, repairs to failed oscilloscope PSUs, etc.

Chris Williams

[mag_therm]

Hi Chris,
Did you read the comment by T3s14CO1L over on your other thread?
For my own interest I started simulation of the flyback feeding the voltage doubler and I agree with T3s14CO1L that the 125 V supply may be problem.
The two 1 uF capacitors in the doubler mean that the inverter will not run in flyback mode during start or maybe at a load step.
Also  the TVS rating should be checked while the inverter is in current limit trying to charge the doubler capacitors.

I just restarted the sim for 5000 usec with 1 nanosec time steps, it will take a while to get results to show how long the inverter takes to
get into flyback mode. ( model just has constant pulse width so not really like the real one.)
Regards

[Labrat101]

Hi ,
Interesting project . Thanks for that link . I read all of the links etc .The schematic seems nice and quite straight forward .
 I guess you realise that is not a standard CRT he used . its not a scope tube .
and works without deflector coils .
 I might be tempted to build this . and run the XYZ outs straight to my  HP or Tech CRT scope. His finished clock look nice in that perspex tube.
I did have another idea I think I recall I have an old Car dash TV with a Black & White CRT which has all the tube power etc . and just XYZ to that .
 Not as cool as green .
   have and good Luck
 

Update this guy has CRT   https://www.sphere.bc.ca/test/crts.html
 Never used them .. prices look reasonable

[james_s]

I have one of the original Cathode Corner scope clocks I built sometime around 2003, I remember on the forum when David Forbes was developing those he mentioned that the power transformer was the hardest part. The original design used a off-line SMPS that runs straight off 120V.

Looks like the nixie watch part of the cathode corner website was updated in 2018 and his email address is listed on there, you might try contacting him directly. He seemed like a nice guy when I dealt with him back in the day.

[Labrat101]

They are Electrostatic tubes I think this model was first manufactured around the early 60.The early Heathkit scope used one . They good for number display .Also used in the old military equipment on mobile Radar 
Also they only need about 1kv and about 600v on the focus .
 with quite a low power consumption  .

[james_s]

Many different tubes have been used in scope clocks, the original Cathode Corner clock used a Chinese 3RP1A which was used in some scopes in the 70s-80s as well as other things. It does need to be an electrostatic tube although there's no reason you couldn't make one with a more modern electromagnetic deflection tube but you'd need to rewind the vertical yoke as I did in my 5" vector monitor. Magnetic deflection vector monitors also use quite a bit more power than electrostatic and they run hot.

[Datman]

You can buy it on ebay:
https://www.ebay.com/b/crt-clock/bn_7024954714