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 Post subject: XY Scope Project
PostPosted: May Wed 02, 2018 12:12 pm 
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Location: Baton Rouge, Louisiana
The goal here is to create an xy scope to use for display, clocks, vector graphics, and similar.
The CRT
Attachment:
crt.jpg
crt.jpg [ 54.46 KiB | Viewed 1230 times ]

A plan is always a good thing
Attachment:
plan.jpg
plan.jpg [ 70.14 KiB | Viewed 1230 times ]
\
The front piece is the obvious starting point, and a neck bracket
Attachment:
bracket_blanks.jpg
bracket_blanks.jpg [ 93.59 KiB | Viewed 1230 times ]

A base will be needed
Attachment:
base_glue-up_1.jpg
base_glue-up_1.jpg [ 44.92 KiB | Viewed 1230 times ]

Check the parts for aesthetic proportions
Attachment:
mock_up_1.jpg
mock_up_1.jpg [ 79.88 KiB | Viewed 1230 times ]

Fasten and glue
Attachment:
glue_up_3.jpg
glue_up_3.jpg [ 88.23 KiB | Viewed 1230 times ]
Attachment:
front_glue_up.jpg
front_glue_up.jpg [ 55.72 KiB | Viewed 1230 times ]

More photos to come.

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 Post subject: Re: XY Scope Project
PostPosted: May Wed 02, 2018 12:18 pm 
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The finishing has begun
Attachment:
first_coat_1.jpg
first_coat_1.jpg [ 126.36 KiB | Viewed 1229 times ]
Attachment:
first_coat_2.jpg
first_coat_2.jpg [ 115.41 KiB | Viewed 1229 times ]
Attachment:
front_first_coat.jpg
front_first_coat.jpg [ 93.68 KiB | Viewed 1229 times ]

Make sure the parts will fit
Attachment:
test_fit.jpg
test_fit.jpg [ 35.33 KiB | Viewed 1229 times ]
Attachment:
test_fit_2.jpg
test_fit_2.jpg [ 47.51 KiB | Viewed 1229 times ]

More to come.

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 Post subject: Re: XY Scope Project
PostPosted: May Wed 02, 2018 2:35 pm 
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Location: Yukon, OK USA
It is always fun to combine two of your interests to make something cool. Looks like a fun project and will certainly be one of kind. 8)

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 Post subject: Re: XY Scope Project
PostPosted: May Wed 02, 2018 3:51 pm 
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Location: Portland, TN, USA
Very nicely done, Mark.

A CRT never had it so good!

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 Post subject: Re: XY Scope Project
PostPosted: May Thu 03, 2018 6:13 pm 
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Very nice indeed!


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 Post subject: Re: XY Scope Project
PostPosted: May Thu 03, 2018 7:24 pm 
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Wooden it be nice if all projects looked this good. :wink:


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 Post subject: Re: XY Scope Project
PostPosted: May Thu 03, 2018 7:39 pm 
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Location: Wayside, NJ Monmouth
Quote:
Wooden it be nice if all projects looked this good. :wink:


Bad pun. But funny


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 Post subject: Re: XY Scope Project
PostPosted: May Thu 03, 2018 10:25 pm 
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Location: Whiteville, TN
Nice wood! Nice wood work! Neat idea!

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 Post subject: Re: XY Scope Project
PostPosted: May Fri 11, 2018 8:00 pm 
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Lovely wood work! Nice to see the beauty of the crt displayed in a project.


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 Post subject: Re: XY Scope Project
PostPosted: May Wed 16, 2018 10:45 pm 
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Thanks for the compliments, fellows.
Here are a few updates.
I felt the need for another coat or two of shellac Saturday morning. Without giving much thought to the weather, I proceeded.
It was a bright sunny morning, a little warm, but what I didn't know was that the humidity was in the 90% range.
The shellac blushed. I spent the rest of the day trying to save it. The final save was a heavy wet coat of brushing lacquer.
Some damage was incurred, but that is the nature of the beast.
After allowing the heavy lacquer to dry for several days, it was sanded and sprayed. I left it in the sun 15 minutes too long and it blistered. Darn. Not bad, and certainly repairable, but still.
The wood frame had to have some relief carving to accept my transformers. Not pretty, but it will not be seen.
Attachment:
carved_up.jpg
carved_up.jpg [ 99.9 KiB | Viewed 992 times ]

Here are the brass chassis plates.
Attachment:
chassis_plates.jpg
chassis_plates.jpg [ 97.78 KiB | Viewed 992 times ]

The transformers fit well.
Attachment:
xfmrs_mounted_1.jpg
xfmrs_mounted_1.jpg [ 103 KiB | Viewed 992 times ]
Attachment:
xfmrs_mounted_2.jpg
xfmrs_mounted_2.jpg [ 121.86 KiB | Viewed 992 times ]

A bottom view, that is the plate transformer.
Attachment:
bottom_view.jpg
bottom_view.jpg [ 69.92 KiB | Viewed 992 times ]

More to come.

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 Post subject: Re: XY Scope Project
PostPosted: May Sun 20, 2018 5:28 pm 
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Progress was made this weekend.
Normally I don't officially breadboard a project, but this time I felt it to be a requirement because a planned schematic with
component values is not being followed, it is being developed, instead
Here is the breadboard for the HV power supply. Notice that I didn't have the correct capacitors, so they had to be built up from what I had.
Attachment:
breadboard.jpg
breadboard.jpg [ 72.09 KiB | Viewed 918 times ]

Here is the scope, ready to fire up for the first time.
Light cigarette and power it up!
Attachment:
ready_to_test.jpg
ready_to_test.jpg [ 69.62 KiB | Viewed 918 times ]

Wow! We have a spot!
The cell phone camera doesn't capture it well. The spot is really much smaller.
This tube has P7 phosphorous.
Attachment:
spot.jpg
spot.jpg [ 24.31 KiB | Viewed 918 times ]

The green persistence is a better indicator of the spot size and shape.
Attachment:
spot_persistance.jpg
spot_persistance.jpg [ 26.61 KiB | Viewed 918 times ]

Obviously, there is some work to be done on the HV section, but hey! Not bad for a first light!

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 Post subject: Re: XY Scope Project
PostPosted: May Mon 21, 2018 6:20 am 
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That thing is pretty cool, can't wait to see what you fix with it.


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 Post subject: Re: XY Scope Project
PostPosted: May Mon 21, 2018 10:27 am 
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db gain wrote:
That thing is pretty cool, can't wait to see what you fix with it.

Well, so far it has helped fix itself.
The intensity control had no effect.
Inspection of the breadboard revealed the lead to grid 1 on CRT had broken off the wiper lug on the pot.
After that repair the spot was very adjustable.
The circuit fault can clearly be seen in the photo labeled "breadboard.jpg".
The red wire on the bench should goto the wiper of the left most pot.

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 Post subject: Re: XY Scope Project
PostPosted: May Tue 22, 2018 1:31 am 
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What CRT is that?

If it is a 5" CRT and you don't have a circuit for driving the deflection plates I've got something I am working on which is a modification of a design built by someone else for 3" CRTs so that it works with 5" CRTs.


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 Post subject: Re: XY Scope Project
PostPosted: May Tue 22, 2018 10:45 am 
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Tube Radio wrote:
What CRT is that?

It is a 5UP7.
Tube Radio wrote:
If it is a 5" CRT and you don't have a circuit for driving the deflection plates I've got something I am working on which is a modification of a design built by someone else for 3" CRTs so that it works with 5" CRTs.

Well, I was planning on something like 6GH8's driving pairs of 6CZ5's in push pull.
BTW, why would you need to mod the deflection amps for 3" or 5" ?
Either should work, right? In fact, some 5" tubes take less voltage per inch of deflection than some 3" tubes.
Do you see it differently?

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 Post subject: Re: XY Scope Project
PostPosted: May Tue 22, 2018 4:49 pm 
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It would need to be modded due to the higher capacitance of the deflection plates in the typical 5" CRT such as the one you're using.

Also it needed to be modded to add compensation in the form of trimmer caps so the bandwidth can be increased to make the image better.

Plus I had to mod the B- supply for a higher voltage since most 5" CRTs require a higher voltage than what most 3" CRTs require.


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 Post subject: Re: XY Scope Project
PostPosted: May Fri 25, 2018 3:01 am 
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Location: Powell River BC Canada
Nice project. Do shock and fire-proof it, and remember it is a large high vacuum
tube capable of scattering glass if broken.

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 Post subject: Re: XY Scope Project
PostPosted: May Sun 27, 2018 6:05 pm 
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I have hit a road block.
Keep in mind that so far, this is strictly an xy scope.
No provision for horizontal sweep exists.
The spot will not focus to a dot, but rather a vertical line.
When I move the horizontal position the problem waveform manifests itself.
All indications are that this is magnetically induced.
When I pull the crt away from the transformers, the spot becomes more of a spot instead of a line, but does not become perfect.
When the focus is adjusted as well as it can be and the power is killed, the spot becomes perfect until it disappears.
I have not had any results with attempting to shield the crt.
Any ideas?
Attachment:
trace.jpg
trace.jpg [ 16.4 KiB | Viewed 752 times ]

Edit: I took the crt out and moved it some distance from the chassis and the spot becomes perfect, no wave form manifests itself.
So, shielding seems to be a viable fix, but steel had no effect. Perhaps mu metal?

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 Post subject: Re: XY Scope Project
PostPosted: May Mon 28, 2018 9:22 pm 
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Yes use MU metal.

Best to find a CRT shield as it will already be in the correct shape.

Also ensure that all power supplies have as low of a ripple voltage as possible.

Do you have a separate astigmatism control?

If not add a 1 meg control across the B+ supply for the deflection amps.

For best focus the astig control should be adjusted to the average DC voltage that will be on the deflection plates.


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 Post subject: Re: XY Scope Project
PostPosted: May Mon 28, 2018 9:29 pm 
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Mount any transformer handling 60 cycles behind the CRT. If mounted near the neck or further forward 60 cycles will have an effect on deflection. MU metal shield will work. Not the same as wrapping metal around a CRT.

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