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Slight;y OT CRT question


Greg Muir
 

Although a slightly off topic subject nothing better to ask a scope group this question.

In the process of mentoring a young individual with regards to basic electronics I dug out an old Heathkit oscilloscope form my junk pile and decided to fix up for him so that he would begin to learn a little more about analog signals. But After firing it up I discovered that the CRT emission is weak and that the scope traces take a little concentration to see.

This particular scope uses a 5DEP1(F) CRT. I my search for a replacement I learned that the are a few used CRTs available which also sport a (S) suffix on their part number. The few data sheets that were found do not allude to the differences between the (F) and (S) suffix tubes. I am making a basic assumption that this refers to the face of the tube being either flat or spherical shape respectively.

Any ideas?

Thanks,

Greg


Michael W. Lynch
 

Greg wrote:
This particular scope uses a 5DEP1(F) CRT. I my search for a replacement I learned that the are a few used CRTs available which also sport a (S) suffix on their part number. The few data sheets that were found do not allude to the >differences between the (F) and (S) suffix tubes. I am making a basic assumption that this refers to the face of the tube being either flat or spherical shape respectively
I think that I read somewhere that this indicates the write speed of the phosphor. S for slow and F for fast. This may not be accurate.

--
Michael Lynch
Dardanelle, Arkansas


Albert Otten
 

At the CRT page Sphere often mentions flat face for 5xxx(F) tubes. In one case, 5UP1(F), the description explicitly states "Electrostatic CRT with flat face (F)".
Albert

On Thu, Jun 4, 2020 at 08:44 PM, Michael W. Lynch wrote:


Greg wrote:
This particular scope uses a 5DEP1(F) CRT. I my search for a replacement I
learned that the are a few used CRTs available which also sport a (S) suffix
on their part number. The few data sheets that were found do not allude to
the >differences between the (F) and (S) suffix tubes. I am making a basic
assumption that this refers to the face of the tube being either flat or
spherical shape respectively

I think that I read somewhere that this indicates the write speed of the
phosphor. S for slow and F for fast. This may not be accurate.

--
Michael Lynch
Dardanelle, Arkansas


Greg Muir
 

Thanks Michael, Albert.

Michael, the data sheets for this tube do indicate that there are different phosphor options available for different writing speeds so I think that the speed is defined by the phosphor given that standard theory.

Albert, I believe that your observation of the suffix is true. As to why they offered both features is beyond me. As for a 5UP1 being interchangeable with the 5DEP1, I first thought that I could go ahead and pick a 5UP1 up but later found that it has a much lower deflection sensitivity. Otherwise it would be a fit.

There is one (F) tube on the auction site that I wanted to get and looks to be in good condition but the seller never responded to any of my offers nor emails. I think there might be a possibility that they may have fallen prey to the virus. Anyone else have this problem with purchasing things recently?

Greg


 

the (F) suffix for CRTs always indicates a Flat Face. a 5UP1 has a
spherical face, but a 5UP1(F) is flat (these tubes only come from Japan, the US makers did not offer this variation). I have never seen an (S) suffix in real life, maybe someone has added that to distinguish between the flat and spherical versions of the same tube.

the 5DEP1(F) was a very popular CRT for low end scopes, it has very high brightness with low anode voltages, and good deflection sensitivity, coupled with a flat face, and you have the makings of a very nice lower frequency (10-20Mhz) scope.

we do have some if you need one (although not so cheap), see:
https://www.sphere.bc.ca/test/crts.html
they also show up on ebay regularly, as they were used in many 5" low end scopes and kits.
often new tubes from un-built kits show up at a good price.

all the best,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
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