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-   -   Anyone ever repair a B&K 470? (http://www.videokarma.org/showthread.php?t=259379)

TinCanAlley 08-30-2013 08:33 PM

Anyone ever repair a B&K 470?
 
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I have this unit and just had to resolder one of the main capacitors as the lead just pulled out of the board. After doing this, I was able to set the proper heater voltage, G2, G1 and test the emissions of the color guns (all tested fine). I wasn't, however, able to test the leakage of the heater or G1. The meter would drop immediately to 0 for both tests on all three guns. I'm pretty sure there is something wrong as this tube wouldn't provide the brightness and image it does if there was a major leakage in all the guns and heater.

So anyone here ever repair one of these units? I was able to get the schematics and parts list, but the only thing the service manual has is how to calibrate the heater voltage of the unit, nothing else. I'm hoping someone can point to an area for inspection/repair.

Findm-Keepm 08-30-2013 10:07 PM

No leakage (G1) or heater-cathode leakage is indicative of a good CRT. I've seen only a few (out of many hundreds tested) that had any leakage. I own 4 B&K 470s, one is my original from the early 90s, and three were passed on to me when my dad died. All 4 had the crappy plastic case hinge fail - I use a piano hinge and some self-tapping screws to replace it. The latches on three are also broken - Velcro cloth and some rubber cement fixed that.

As long as you can set the line adjust, G1 and G2's, and your CRT shows emission, I'd say you have a good 470. They are workhorses.

Cheers,

radiotvnut 08-30-2013 10:09 PM

No, there's nothing wrong with it. When testing for leakage or shorts, the pointer should go to 0. If the pointer rises on any of the leakage test functions; then, a short or leakage is indicated.

TinCanAlley 08-30-2013 10:32 PM

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Hmmm... The manual says as long as the needle is in the yellow section, the leakage is acceptable. The 0 mark is just outside the yellow section, so I figured something wasn't right. I guess 0 is the start of the yellow section.

radiotvnut 08-31-2013 12:53 AM

As long as it doesn't rise out of the yellow, the tube is acceptable. Actually, I don't think I've tested a tube where the leakage test registered in the yellow. It either didn't move the pointer or it had full blown leakage/short.

TinCanAlley 08-31-2013 10:45 AM

Quote:

Originally Posted by radiotvnut (Post 3081072)
As long as it doesn't rise out of the yellow, the tube is acceptable. Actually, I don't think I've tested a tube where the leakage test registered in the yellow. It either didn't move the pointer or it had full blown leakage/short.

Good to know. Then with a "0" result added to the other results, this CRT is in fine shape.


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