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Old 07-23-2009, 10:01 AM
jshorva65's Avatar
jshorva65 jshorva65 is offline
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Join Date: Jun 2002
Location: Ohio
Posts: 358
"Cathode Restorer" CRT Tester Question

I wasn't sure where to post this Early Color (and/or B/W) TV Test Equipment question. Early Color TV seems like as good a place as any, I guess. Does anyone know where I might find a schematic for a REM Electronic Instrument "Cathode Recovery Unit and CRT Tester" (no model number found on either the exterior or interior of the unit, its only included documentation is a single page of operating instructions on the inside top cover)? According to legend, at least, this unit is a direct ancestor of the Beltron model 2972-E "Cathode Recovery Unit and CRT Tester" device. I have heard very good reviews of this unit from a colleague in Akron and of the Beltron from another colleague. I just purchased one of these REM units recently. Since "Big Dave" is a fellow native of Warren, Ohio who currently lives just across town from me and owns a Beltron 2972-E, he and I compared test results for some tubes between his Beltron 2972-E, my Sencore (just calibrated per its manual's calibration procedure) CR-168, my B&K 465, and my newly-acquired REM tester. It is clear from the tests of these known-good tubes with our known-good testers that the REM unit is in need of repair.

I began troubleshooting without a schematic, locating and replacing any components found to be out of tolerance. I re-formed a 16uF/450V capacitor and confirmed it to be in good condition, and replaced three 47K and three 100-ohm resistors (located in each gun's meter circuit, the 47K in series with and the 100-ohm shunted across each meter) which were outside rated tolerance with new units measuring within 5% of nominal values. Still, tubes which test as Good or Excellent on the other three testers are showing Bad on this one. There is a large "potted" circuit assembly (about 2-1/2" diameter and 3/4" thick) inside the unit, with several leads connected to the various switches, meter movements, and other discrete components. To troubleshoot the device further, I will need to determine the contents and connections of the "black box" assembly.

The key advantages of this model over some others (such as the Sencore and B&K units I mentioned) are: its use of a limited-current Recovery process instead of the capacitive-discharge "flash" method which tends to cause "cathode stripping" and destroy tubes; individual meter movements for all three guns in Test mode; and a built-in mechanical timer for the Recovery function. Its disadvantages are: absence of a Short test function; fixed Heater voltage (for use with 6.3V tubes only); absence of Gun Balance provisions (both the B&K and Sencore units can set fixed "balance" points via variable G2 voltages from which some calculations can determine whether Balance and Tracking are acceptable); and absence of a Tracking test (only the Sencore can provide a direct "Good/Bad" Tracking reading directly, while Tracking quality can be determined indirectly via calculations applied to test readings from the B&K). The Beltron 2972-E supports Heater voltages other than 6.3V, but also lacks direct tests for Shorts, Gun Balance, and Tracking.

Here are some photos of the REM Electronic Instrument "Cathode Recovery Unit and CRT Tester."
Attached Images
File Type: jpg REM CRT Tester 001.jpg (77.1 KB, 18 views)
File Type: jpg REM CRT Tester 002.jpg (85.2 KB, 26 views)
File Type: jpg REM CRT Tester 003.jpg (74.7 KB, 13 views)

Last edited by jshorva65; 07-23-2009 at 10:05 AM.
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