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  #61  
Old 10-06-2011, 01:33 AM
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You're right, as usual. lol

5.6k resistor was feeding the vertical output transformer, and the vert height pot was in fact guilty of carbon tracking. Looks to me like it had found a path from the carbon element to case ground, but I don't have a suitable replacement...

Any help?
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  #62  
Old 10-06-2011, 12:22 PM
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First time I saw a carbon comp resistor crack length wise. Next power up you might want to pull some tubes and power up a few sections at a time so as to minimise the chance of frying something less replacable.
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  #63  
Old 10-06-2011, 11:25 PM
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Only other thing in that circuit is the vert transformer, which is not really in any danger. Found the bad section in the pot, it was arcing right to the case.




Robbed a replacement element from a doner chassis, put it back together. Here goes round #2...
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  #64  
Old 10-07-2011, 01:35 AM
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New issue...

Put the chassis back in, fired it up. HV is clearly working, I can see blue glow from the shunt regulator. But when the anode lead is connected to the tube, I get this sizzling sound like it's shorting to something. I'm reasonably sure I have the CRT installed correctly: anode clip, rubber boot, mumetal shield, retaining bracket, ect. Anything that could cause the anode to sizzle that I'm not aware of? Tried another HV boot just in case it had a hole or something, same result.
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  #65  
Old 10-07-2011, 07:48 AM
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I've had that, or something similar, happen to a Merrill that hadn't been under power for an extended period. I cleaned the boot, particularly inside, and the interface between the flange and glass. It finally stopped frying. Never found the exact cause though.

Pete
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  #66  
Old 10-07-2011, 11:19 PM
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The Merrill oracles have spoken, and they are right as usual!

Cleaned the heck out of the CRT and insulating boot, ladies and gentlemen we have....something!






Obviously, the thing still has a lot of issues. Vertical is working, though it's not near as tall as it should be. HV and HO cathode current still need to be checked. But at least I have proved that this thing still works, which means the cabinet needs to go to the refinishing guy ASAP. Think I'll finally buy my own HV meter this weekend, unless Wayne or Mark would like to pay the Merrill in a window a visit.
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  #67  
Old 10-07-2011, 11:53 PM
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Its Alive! For a HV probe, I recommend one that plugs into your DMM, not one with a meter built into the handle.
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  #68  
Old 10-08-2011, 01:51 PM
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That is great to see. Once you have light on the CRT face, you are 90% there.
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  #69  
Old 10-08-2011, 02:53 PM
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Of course it's just the other 10% that's so damn aggravating....
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  #70  
Old 10-08-2011, 03:25 PM
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Quote:
Originally Posted by David Roper View Post
Of course it's just the other 10% that's so damn aggravating....
Speaking of which...


I was a dumbass and decided to twiddle around with the IF alignment, since I wasn't passing a video or audio signal at all. Should have done some voltage measurements first, damn tuner wasn't getting any B+! The alignment wasn't far off thankfully, I only had to tweak a few transformers to get it looking respectable. But I followed the loss of power back to it's cause, which ended up being the field neutralization pot on the LV cage.



This isn't a normal pot though, it's tapped in the center. Anyone have a spare they could donate to the cause, or know of one that's available on the open market? I suppose this would explain the excessive B+ voltages as well, since half the chassis wasn't being powered.
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  #71  
Old 10-09-2011, 08:45 PM
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Talking

Murphy's Law says it takes 95% of the time, money, and efforts to complete the first 90% of the project and 95% of the time, money and effort to complete the last 10%.
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Last edited by reeferman; 10-11-2011 at 10:24 PM.
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  #72  
Old 10-09-2011, 10:13 PM
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Quote:
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Murphy's Law says it takes 95% of the time, money, and efforts to complete the first 90% of the project and 95% of the time, money and effort to complete the last 10%.
HUH! I think Murphy needs to brush up on his math. Or am I missing something here?

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  #73  
Old 10-09-2011, 10:22 PM
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Quote:
Originally Posted by miniman82 View Post
This isn't a normal pot though, it's tapped in the center. Anyone have a spare they could donate to the cause, or know of one that's available on the open market?
Mark Oppat has load of controls. He also rebuilds them.

http://oldradioparts.net/controls.html

Phil Nelson
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  #74  
Old 10-09-2011, 10:47 PM
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Thanks for the link, Phil. John Folsom says he has one to send me, but I might pick up a spare if Mark has one.
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  #75  
Old 10-10-2011, 12:15 AM
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Murphy's Law says it takes 95% of the time, money, and efforts to complete the first 90% of the project and 95% of the time, money and effort to complete the last 10%.
That is how my hot tub project has seemed to go.
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