Waterman 'scope for NBTV

[Marcus]

Hello KG6KGG,

I have one of these pocketscopes also. Mine is still functioning so I haven't contemplated replacing anything yet.
I have all replacement tubes if you need them let me know. I would suggest that replacing all the capacitors is a good start (although I haven't). Or you could just bring it up to full voltage slowly to see how you go?

I have had a project on the boil for ages based on the pocketscope circuitry for an all tube pal display triggered by a nixie alarm clock...
One day I will finish it, It needs a bit more work in the video amp section at the moment.

[KG6KGG]

Marcus:

Below is the text of an email exchange I had today with a fellow here in the states who has a website with some information of the Waterman S-10. He also has a schematic on how to display video on a scope. (Of course he was doing it with 525/30 NTSC video). I was asking him about how to display NBTV 30/12.5 video on it. He graciously replied with some technical information on how it might be done on this little scope.

As you can see the Waterman is not very capable... however it might just be possible to display NBTV on it. And, that would be fun!

Here's the text of the email:

From: Jon Stanley [mailto:Philcogrump@aol.com]
Sent: Thursday, February 05, 2009 1:13 PM
To: Szasz, David A. (CSI)
Subject: Re: Restoration of Waterman S-10A Scope?

Hi Dave,
Congrats on winning a nice little 2" scope. If the seller was able to get the CRT lit then you are in pretty good shape. The tubes are probably still good. The only thing you would need to do is recap the scope then it should work fine for a while. If I recall correctly, there are probably only two 22uF 450V electrolytic capacitors and maybe 5 to 8 paper capacitors in the range of 0.001uF to 0.1uF. No need to replace the mica capacitors if there are any.

I thought about adding a Z axis to the Waterman but I wasn't too certain of the Z-axis performance because the scope is very very simple. The scope probably could handle slow TV signals, but NTSC is questionable. The Waterman has a built in sweep that can be triggered via HOR/SYN with the horizontal function set to EXT, so feed that the horizontal sync of the 30-line signal, I think that'd be 350-ish Hz or something? The vertical you'd need to build a sweep oscillator running at 12-ish Hz, could be done with tubes or transistors, take a look at my TV-Scope converter circuitry but crank down the vertical frequency from 60Hz to 12Hz or so.

If you look at the schematic for the Waterman S-10A (http://www.electronixandmore.com/misc/waterman.pdf) then notice that the CRT grid (pin 10) connects to the brightness control via R19. Since R19 is in place, it already serves as a grid resistor so you could simply disconnect C14 from ground and feed the Z axis modulation through C14. However, I have no idea if it would even look any good. You'd need at least a 20-30V Z-axis modulation I would think, and be careful because C14 is the only isolation between you and -100 to -200V in the scope.

Let me know how your project comes along. I've been fascinated in mechanical TV for some time. I even tried building my own color 32-line camera but never really got far because the photodiodes I used need an enormous amplification gain. A PMT might do the trick. Someday...

Jon




On Feb 5, 2009, at 11:51 AM, Szasz, David A. (CSI) wrote:

> Hi:
>
> After several tries I have finally won an auction on Ebay for a Waterman S10A "Pocketscope."
>
> 1.) I would like to ask for your suggestion for the best approach to restoration of this classic device. Should I just replace all the capacitors and test the tubes to start or what? The prior owner plugged it in and the CRT still lit-up so it should be possible to get it to working order.
>
> 2.) Is there a simple way to modify this scope to display 30-line NBTV signals? I am into the mechanical TV hobby... but have little experience with vacuum tubes. thus the interest in the Waterman S-10. It looked simple enough for me to understand...
>
> Though it lacks a second channel and "Z-axis." I have seen articles on adding a second channel, so perhaps it could display very simple graphics.
>
> Anyway I just cant wait for this little cutie to arrive on my doorstep.
>
>
> Thanks for your advice, love your website... it's very inspirational
>
> thanks
>
> Dave Szasz - KG6KGG

=

[Steve Anderson]

Anyway, what would be your recommendations on restoring this relic from 1947? According to the previous owner the CRT still lights up, but that’s all I know till it arrived here by surface post. Dave – KG6KGG

Hi Dave,

First, if you have no spare tubes at least find a local source of them and the main filter capacitors, C12 and C13, I would replace these caps as a matter of course, the originals are some 50 years old! Be prepared to replace the pots too. Have some switch cleaner handy as well. There is no fuse in the power input, I suggest somehow arranging an external 1A one, even if only temporarily.

When it arrives take a few photos as a record. Remove the tubes and unplug the CRT, measure the insulation of the transformer windings (both primary and the secondaries) as well as their resistance (marked on the circuit diagram). If all looks well plug it in and measure the AC voltages on the secondaries of the transformer, they will be a bit higher than on the circuit due to no load.

Carefully put your ear near the transformer and make sure it's not buzzing of humming excessively. If all looks well leave it on like this with no load for 30 minutes say and frequently check that it's not getting too hot, it will be a little warm, but not hot.

Plug in the CRT only and see if the heater lights up (assuming you can see it, on some CRTs you can't). Then do the same one-by-one with the other tubes except the 6X4 (EZ90) rectifier. Set up a voltmeter across C12 and if you have a second one put it across R17 to keep an eye on the current. Turn the intensity control fully anti-clockwise.

Now this is where a Variac (variable auto-transformer) comes in very handy where you can slowly increase the mains voltage. But in the absence of one go for broke, plug in the 6X4 and turn it on.

After 30 seconds or so the voltage across C12 should be 'near' nominal, perhaps a bit low, the voltage across R17 should only be a few volts, say less than 20. All the time keep one hand on the power switch!

If there is no smoke or troublesome smells slowly wind up the intensity control and hopefully you'll at least see a spot or trace. Depending on what you find at this stage will depend on what you need to do next.

This CRT is being run at a very low voltage, see attached datasheet where in the 'Recommended Operating Conditions' they specify 1000V, at only 360V it will not be bright and the focus not that wonderful either. In fact I'm surprised it works at all!

Steve A.

Added later...I have found a datasheet that has operating conditions for 500V but not as low as 360V.

[KG6KGG]

Thanks everybody.... You know I should really invest in a Variac. A number of years ago I pluged in an old valve based Hallicrafters S-38 and damn near burned down the house! Well, this radio had a hot chassis...a few sparks flew that day!

The fuse is an excellent suggestion. I plan to take things slow, This scope is older than my brother and he's 60 ish.

Thanks Again

Dave

[Marcus]

Jon has alot of great projects on his site,

His site is where I have got the circuit for the all tube display using a relaxation oscillator. I'd be interested to see if you can get something going for NBTV to work with the scope.

[KG6KGG]

Here's a few pics of the scope off of Ebay... As you can see they plugged it in and there is a spot on the CRT... if this is the tightest the beam is then the design may be running the tube at a lower voltage than it was specified for.

Well, I'll have to see when the scope arrives in the mail.

[Steve Anderson]

Here's a few pics of the scope off of Ebay... As you can see they plugged it in and there is a spot on the CRT... if this is the tightest the beam is then the design may be running the tube at a lower voltage than it was specified for. Well, I'll have to see when the scope arrives in the mail.

Well that spot is somewhat large, perhaps the person selling it had no idea about 'scopes and didn't adjust the focus.

Depending on how 'original' you wish to keep the instrument you could implement some modifications, you're gonna have to anyway if you wish to add video modulation.

Those that like to keep old things original better stop reading this right now. My thoughts that follow will upset those as they involve a rebuild and it will be nothing like it is now. I'll post those thoughts later...

It appears from the photos that it's not earthed/grounded. Add one, even at 110V.

Steve A.

Attached is the other data I have for the 2AP1. Note the remark on page two, "Brilliance and definition decrease with decreasing anode-No.2 voltage. In general, anode-No.2 Voltage should not be less than 500 volts."

[KG6KGG]

Steve:

Thanks again for your observations. A few months ago while bidding on another one of these scopes and reviewing the CRT specs and schematic. I thought that the voltage was a little low from the transformer. At the time I just attributed it to my general ignorance on older "hollow-state" technology.

Well, first I'll "recap" it, add a fuse and three prong plug. Maybe it has a ground terminal on the case, but I doubt that? Building electronics with the third prong didn't become common here in the states till the mid 60's I think. (It's always a good idea to be well grounded... by the way take it from me 110 volts has a bit of bite to it too.

[Steve Anderson]

....Building electronics with the third prong didn't become common here in the states till the mid 60's I think. It's always a good idea to be well grounded... by the way take it from me 110 volts has a bit of bite to it too.

Just 50V can give you quite a 'tingle'. Here having gounds/earths on outlets only became written into legislation about five years ago, so many houses, offices and factories still only have 2-pin outlets, and this is at 220V! The legislation is not retrospective and only applies to new installations.

When I bought this house the first thing I did was get an electrician in and told him to rip out all the existing wiring, sink an earth-rod and do it properly. Which after fashion he did, I got him to re-do one or two bits but this place is now safe.

Steve A.

[KG6KGG]

Yes, quiet

The way it was supposed to work here in the old days was that the electrical outlet box was supposed to be grounded and that the piece of equipment would be connected to the middle screw on the wall outlet. This was rarely put into practice though... which led to new code revisions.

In my old house on the east coast (built in the 40's) I had to have all the outlets redone so that the electronics would be safe and wiring to code. Most house inspectors look the other way when a property is sold... besides I think every state has a different law on this matter, and we have 50 states... What a mess!

[KG6KGG]

Here are some pics of Leo, my lab assistant with the Waterman scope from a few days ago. As you can see the scope is even smaller than the cat!

Leo is an unrepentant power cord biter. I wave tried swabbing them with Tabasco sauce to keep him from nipping, to no effect. Perhaps if we had 220 volt service here instead of 110 volts his learning curve would be faster?