CurtPalme.com Home Theater Forum

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Just wondering...has anyone ever used a CRT rejuvenator/restorer on any of the projection CRTs that we enthusiasts
usually encounter?

If so, how well did it work?

barclay66 · Posted: Wed May 11, 2016 8:24 am Post subject:

Hi,

I've successfully used a CRT Analyzer/Restorer for two purposes:

- Removing shorts. I had a green tube which had some kind of static noise and jumps in brightness. After removing the short between G1 and the cathode it became perfectly usable. Removed another short from a blue tube of one of our fellow forum members.

- Matching tubes. For each tube in my inventory I measured the beam current at different G1 voltages (this is being done by measuring the cathode current and lowering the G1 voltage from 200V to 0V in 10V steps; no HV applied; tube alone on the bench). That allows for the calculation of the expected brightness at different drive levels as long as phosphor wear has been ruled out previously. Plotting the data into a chart lets You select tubes that have a matching sensitivity and linearity.

Example: The chart below shows the results of three tubes. All tubes show no aging of the phosphor whatsoever (typical for red tubes). The upper curve is from a slightly used LUG tube. The one in the middle is from a new LCP and the lower one from a used LCP.
As You can see, the LUG has an inherent elevated sensitivity and a flatter response. Instead, the used LCP has quite a weak response at lower G1 voltages. Mixing it with newer green and blue tubes would shift Your color balance out of whack at IRE levels below 30.
I wouldn't say that using a matched tube set will eliminate the need of color calibration. But it removes a lot of hassle and increases the chances that You'll get a nice color reproduction out of the box using the Marquee's controls only...

Regards,
barclay66

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Cool. That's about the answer I was hoping for. Thanks.

CIR Engineering · Posted: Fri May 20, 2016 11:21 pm Post subject:

I've used my Sencore CR7000 to fix quite a few shorts. The issue is that many shorts are to the heater and they are not fixable.

craigr

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I have a very dim Thomas P19LUG equivalent tube and I am wondering it it might be restorable.