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  #1  
Old 09-04-2018, 01:28 PM
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Advice on CRT tester/s

I'm getting ready to tackle my mid-'50s Raytheon tv. Before I get started, I want to test the picture tube (17HP4). Since I'm going to need a CRT tester, I want something that I can test my other tvs.

Here is the pic/tubes I want to test:
17" Raytheon 17HP4
21" Philco Predicta 21FDP4 (the replacement type)
13" RCA color c.1986

I see B&K and Sencore units are quite popular. I'd like some advice on what to purchase, and especially the correct adapters I'll need for the picture tubes mentioned above. Thanks.
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Old 09-04-2018, 07:53 PM
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Zsuttle Zsuttle is offline
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Both B&K and Sencore made really well built units, though the general consensus seems to be towards the later built models. (Some people swear by Beltron. I have no experience with their units)

The B&K models 467 and 490(B) are generally regarded as the best models in the B&K lineup. The 470 and 480 being the single meter versions of the equivalent testers.

The Sencore CR70 is the equivalent to the B&K 467/90. The CR7000 is a fully digital tester to complete the icing on the cake.

Personally, the CR7000 is overpriced ($300+) and really doesn't offer much more over its counterparts, as is the 490 ($200+).

A CR70 or 467 will do everything you need to do without breaking the bank. Make sure it comes with adapters, as buying them individually can add up. (If you even find them) The 467 uses adapters 10 and 9 to test the 17HP4 and 21FDP4 respectfully. The CR70 uses the universal adapter (UA) and adapter 4 respectfully.

*side note* The universal adapter can be used to test most tubes if an adapter is missing.

Ultimately, a B&K 467 or CR70 is the best bang for your buck for general tube testing and rejuvenation. Both were designed to accommodate a wide variety of tubes and generally give a good indication of the tube's emmissions.

Hope this helped,
Zach
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Old 09-04-2018, 11:23 PM
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Thanks Z, that's quite helpful. I'll look into those models and try to sort out what would be best for me.
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Old 09-05-2018, 08:07 AM
Chip Chester Chip Chester is offline
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I'm in sort of the same boat, wanting to test the tube on my Sylvania before dim bulb/variac tests. To that end, I found and bought a Sencore CR143 that's complete and in good shape. Found the book online, too, and Dave G. sent me a nice Circuit Digest service guide on the set. But then I started second-guessing myself, wondering how to test the tester. Don't want to hook it up and nuke things before I even get started. The set is a little unique -- a 1958 Halolite Sylouette 21" -- though moreso for its cabinet and control layout than the actual chassis. Ultimately trying to decide if I'm the right guy for the restoration of this VGC set, or should I offer it up to a more-qualified owner?

I've done electronics repair, more in the op-amp audio world than tube TV, but I do have a decent scope or two, test gear (except no HV probe yet), and the ability to read instructions and follow a block diagram thru a circuit. I could not design a TV from scratch, though.

So am I good to go if the tester doesn't have obviously zapped components inside, no smells or smoke when powered up? And I just consult the manual, use the correct adapter, and plug it in to the CRT? Or should I research what voltages should be on what pins, what current they should supply, and verify all that before moving forward?

And in deference to the OP, should I get my own damn thread instead of extending his?
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Old 09-05-2018, 09:09 AM
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ISawItOnTV ISawItOnTV is offline
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Quote:
Originally Posted by Chip Chester View Post
I'm in sort of the same boat, wanting to test the tube on my Sylvania before dim bulb/variac tests. To that end, I found and bought a Sencore CR143 that's complete and in good shape. Found the book online, too, and Dave G. sent me a nice Circuit Digest service guide on the set. But then I started second-guessing myself, wondering how to test the tester. Don't want to hook it up and nuke things before I even get started. The set is a little unique -- a 1958 Halolite Sylouette 21" -- though moreso for its cabinet and control layout than the actual chassis. Ultimately trying to decide if I'm the right guy for the restoration of this VGC set, or should I offer it up to a more-qualified owner?

I've done electronics repair, more in the op-amp audio world than tube TV, but I do have a decent scope or two, test gear (except no HV probe yet), and the ability to read instructions and follow a block diagram thru a circuit. I could not design a TV from scratch, though.

So am I good to go if the tester doesn't have obviously zapped components inside, no smells or smoke when powered up? And I just consult the manual, use the correct adapter, and plug it in to the CRT? Or should I research what voltages should be on what pins, what current they should supply, and verify all that before moving forward?

And in deference to the OP, should I get my own damn thread instead of extending his?
No, you're fine. I've never tested a picture tube before and would like to know the answers to some of the questions you're asking.
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Old 09-05-2018, 06:23 PM
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Notimetolooz Notimetolooz is offline
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In general terms, CRT are tested as triodes. On B/W CRT this means there are five connections, two Heater, Cathode, Grid and First Anode or Grid2.
Color CRT have three guns vs. the single B/W tubes, color heaters share the same connection. There is either a switch to select between the three guns and a single meter or three meters to test the three guns at the same time.
To test for leakage or shorts, various voltages are connected to the elements and any current above a small amount usually lights a neon lamp.
Heater voltages range from about 2.34 V to 12.6 V. Anode voltages range from 30 V to 300 V. These voltages depend on tube type. The cathode current is displayed on the meter for the emission test and the actual current would be indicated good if something around 0.3 ma. or more. Only about 1.5 ma. may be the maximum on the meter.
Cutoff is measured by putting a variable negative voltage on the Grid to reduce the emission down to a certain point.
Clearing shorts is done by charging a capacitor and then discharging the capacitor across the shorted elements.
Various methods are used to "restore" emission, some of them riskier than others. There are different ideas of what works best. Methods range from temporarily boosting the heater voltage a certain amount, and/or increasing the anode voltage, also sometimes using a charged capacitor to provide a pulse of high voltage and current.
You really need to analyze the schematic to figure out the details of a particular tester. Some manuals explain more then others.
This is meant to be a general overview, your mileage may vary.
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Old 09-07-2018, 06:54 AM
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AlanInSitges AlanInSitges is offline
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Admiral Bob (bandersentv here) has tons of videos on YouTube about how to use the CR70 (I think he has another Sencore as well, can't remember). Most of the Sencore models are pretty similar, the main difference being memory functions for comparing the emission balance between different guns of a color tube and additional rejuvenation options.

I just bought a NOS CR161 still in the box with manual, sales receipt, and a 1971 Sencore Newsletter with service tips and news about new products. I got it for $75, it has all the adapters, and powered up and worked just fine right out of the gate. You don't have to buy an expensive one to test 1950s CRTs.
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Old 09-07-2018, 01:20 PM
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Thanks Alan, I'll check out some of Bob's videos.
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Old 09-07-2018, 06:05 PM
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Quote:
Originally Posted by AlanInSitges View Post
Admiral Bob (bandersentv here)
When you say it that way it makes me think VK needs to collectively find and gift to him an aircraft carrier (VK slang for the jumbo 60's TV/stereo combo consoles).
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Old 09-08-2018, 06:37 PM
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I've found the cutoff indication on a Sencore CR-70 to be unreliable at best, and I don't like having to test the three guns of a color CRT in turn.

My personal favorite CRT testers are the various Beltron models. They're all essentially the same; they use an auto-bias circuit, so all you have to set is the filament voltage and wait to see what kind of current you can draw from the cathode(s). In general, if you can pull 0.75 μA from the cathode, the tube will produce some sort of picture.

I modified mine one step further and wired a Sola filament transformer into it. It kicks out a constant 6.3 volts to +/- 3%, up to 5 amps. I just plug the tester in, plug the tube into it, and wait.
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Old 09-09-2018, 06:16 PM
Bill R Bill R is offline
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I have both the CR70 and a 467. I find myself going for the 467 in most cases. I just really like the individual meters for each gun. Both do an excellent job though.
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Old 09-11-2018, 08:16 AM
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ISawItOnTV ISawItOnTV is offline
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Thanks for the replies and info folks, I purchased a nice Sencore CR70.

Now for the bad news: Hurricane Florence appears to be heading my way, and I've got to get things boarded up and readied for a Cat 3/4/5 storm!
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Old 09-11-2018, 11:16 AM
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Good luck. If you plan to evacuate I recommend planning the drive both ways to miss the rain...I know from experience as a passenger that driving the highway through hurricane/tropical storm rains is a very unique form of hell.
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