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 Post subject: Testing 7JP4
PostPosted: Mar Wed 24, 2004 10:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3156
Location: Little Fort (a.k.a.) Waukegan, IL
Will a B&K 465 Crt tester test 7JP4's. Picked one up for under 40.00. Just waiting for it to be delivered. IF anything it might make a good addition to my collection, although I prefer the 40's vintage test equipment from a collectors point of view. <P>Tony<P>------------------<BR>


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 Post subject: Testing 7JP4
PostPosted: Mar Thu 25, 2004 12:07 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 21838
Location: Detroit, MI USA
Hi Tony, <P>Unfortunately the B&K won't test that tube. I have only seen one CRT tester that will check 7JP4's, and it was an older model Philco tester which did not even have a meter, only a neon light to indicate that the CRT had "some" emission. Not really much of a test. Electrostatically deflected CRT's like the 7JP4 have different characteristics than ordinary CRT's and I think that is why very few testers are equipped to check them.<P>I have experimented with making adapters to test the 7JP4 on a CRT tester such as your B&K, as well as on a standard tube tester, with some success, but I prefer to test them in a known working set. I keep a 7" Admiral sitting sideways on a shelf with the back off, and just plug the CRT being tested into the Admiral's CRT socket and lay it on the shelf. In my opinion, this method is far better than a tester, because I can actually see the picture, and by adjusting the focus, brightness, and centering controls on the TV chassis, verify that all functions of the CRT are OK. <P>------------------<BR>Dennis


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 Post subject: Testing 7JP4
PostPosted: Mar Thu 25, 2004 1:46 am 
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Posts: 3997
Location: Connecticut. USA
I agree with Dennis, the best test is the TV set itself, with that said, I did make an adaptor for my "Raytronics Cathode Beamer" model CB-54 and it works ok.<BR>On the Raytronics there is a HV "anode" lead that is needed to check the emission of the tube under test, like the 10BP4, etc.<BR>That lead is seperate and has a clip lead that you connect to the ultor "button" of the CRT.<BR>With mine I used a Greenlee chassis punch on the back of the tester to mount an 8 pin ceramic octal socket.<BR>I made a short harness and connected the HV to the socket inside the tester from the wire that has the clip lead, I used 20KV wire in the harness to a 8 pin octal plug made from an old 8 pin tube I broke.<BR>Of course the other wires in the harness are filaments, cathode, G1, G2 are regular hookup wire.<BR>Note: 20 KV wire is not needed with this, but I had it on hand, the Raytronics puts out appx 2,500 volts DC when it is in rejuvinate mode when used in the highest mode, thats why the ceramic socket.<BR>The other side of the harness I used a socket from an old O'scope I junked that used a 3BP1 CRT, the 3BP1 uses the same socket as the 7JP4.<BR>If I need to test another CRT, I just unplug this adaptor and plug in another, I have 4 adaptors so far, even one for the 3KP4.<BR>Sorry to be so long winded, but I think this tester is one of the best to rejuvinate a vintage CRT.<BR>I am sure you could make something like this for your 465, never owned one but I believe you could.<BR>One last thing I promise.... <IMG SRC="http://antiqueradios.com/forums/biggrin.gif"> You will need a known good 7JP4 as a standard to get the reading so you know where to set the controls on your tester.<BR>WHEW! I hope I did not corn-fuse anyone. <IMG SRC="http://antiqueradios.com/forums/biggrin.gif"><BR>========================================<BR><P>------------------<BR>Bill Benson


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 Post subject: Testing 7JP4
PostPosted: Mar Thu 25, 2004 5:22 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1402
Location: 07450, New Jersey
There is a CRT tester that will test a 7JP4. It is a Precision CR-30. They show up now and again at Flea markets and auction sites. Here is a link to one (not mine):<BR> <A HREF="http://www.radiolaguy.com/equipment.htm" TARGET=_blank>http://www.radiolaguy.com/equipment.htm</A> Scroll to the bottom of the page.<P>I do agree with the other posters though that the best tester can be a working chassis.<P>------------------<BR>Tim


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 Post subject: Testing 7JP4
PostPosted: Mar Thu 25, 2004 6:52 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3156
Location: Little Fort (a.k.a.) Waukegan, IL
Thanks guys, I saw the Precision Crt Tester on the radiola guys site. Mighty high price to pay for something to use once. Only if I decided to concentrate on the early sets would this make the price worth it. But since it fits in the era of test equipment I'm intererted in collecting, just maybe. Well maybe I can use the B&K on my RCA console.<P>BTW Radio Guy has some VT 71's. Just ask.<P>Tony<P><P>------------------<BR>


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 Post subject:
PostPosted: Nov Wed 03, 2010 5:04 am 
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Joined: Jul Thu 31, 2008 6:01 am
Posts: 143
Location: BORDENTOWN CITY NJ
ops wrong topic.


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 Post subject:
PostPosted: Nov Thu 04, 2010 9:42 pm 
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Joined: Mar Mon 16, 2009 12:50 am
Posts: 349
Location: Norfolk, VA
I can't can't tell you which ones will test that tube, but I can tell you that an RCA CR-III won't. My 7JP4 tested dead as a doornail on one, but it's very bright and sharp when connected to the chassis.

_________________
Early Color TV Enthusiast


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 Post subject:
PostPosted: Nov Fri 05, 2010 2:34 am 
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Joined: Jul Thu 31, 2008 6:01 am
Posts: 143
Location: BORDENTOWN CITY NJ
miniman82 are you shore you had your crt test leads connected to the write pins on the tube socket base? If so something is wrong with your tester.

If you want to test a 7JP4 The crt tester also has to be made to test electrostatic Defection type crts aka your 7JP4 3KP4. Most crts are the electromagnetic deflection type. Most crt testers are designed to test only magnetic deflection types only. If you try to test a 7JP4 with this type of tester you will not get a accurate reading!

If you want to test 7JP4s buy a Precision CR-30 or a Raytronics CB-54A or better yet just put the crt in a tv that is the best test for any crt.

John T


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 Post subject: Precision CR-30 CRT Tester
PostPosted: Nov Sun 07, 2010 10:15 pm 
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Joined: Jun Fri 18, 2010 1:49 am
Posts: 255
Location: Davenport, Iowa 52806
I have one here, if anyone is interested.

Jerry


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 Post subject:
PostPosted: Nov Sun 07, 2010 10:34 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4325
Location: Woodinville, WA USA
My Sencore CR70 manual lists settings for the 7JP4. It's tested like a scope tube, using the universal adapter.

http://antiqueradio.org/art/temp/7JP4TestData.jpg

Phil Nelson


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 Post subject:
PostPosted: Nov Sun 07, 2010 11:26 pm 
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Joined: Jun Fri 18, 2010 1:49 am
Posts: 255
Location: Davenport, Iowa 52806
I have a Precision CR-30 CRT checker if
anyone is looking for one.

Jerry


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