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Author Topic: 833A's warning for beginners - be careful not to reverse tube -  (Read 5059 times)
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« on: November 30, 2006, 09:05:05 PM »

Hola!

I'm sure all broadcash OT's know this - and most commercial transmitters make this mistake almost impossible.  But I want to mention a potential mistake easily made by guys who build and first work with 833A's.

Normally, the two pin socket has one flat sided  and one round hole. This insures the tube goes into the socket just one way.  This assumes the socket was installed with a particular orientation and the plate and grid caps are  plugged on correctly.

But what if you are not aware of this socket orientation and mount the sockets "backwards" by forcing the tube in the wrong way? (it will fit sometimes with worn, loose  pins) Or make your own sockets that do not have the flat sided receptacle so the tube can go either way?  Or what if you happen to plug the grid cap onto the plate and the plate cap onto the grid of the tube? The caps are the same size.

My point is that an 833A has a grid and plate cap orientation that must be watched when exchanging tubes. The grid and plate caps may sometimes reach to both caps and if the tube is in backwards, it looks normal.  Unless you look at the inside tube structure, it looks correct either way.

What inspired this post is what happened tonight. I hadn't worked with 833A's in at least ten years. My socket pins were not tight enough to make  the flat side matter.  I put one of the tubes in 180 degrees out. Of course the grid and plate caps were reversed. With no filaments on I tested the high voltage and heard a big snap.  It took a while to figure out what was wrong.

There was no damage done to the reversed 833A, but it could have been a disaster if I had the fils on and/or the filament CT keyed to ground.

Just wanted to get this into the archives to possibly save the life of an 833A or mod transformer in the future.

73,
T
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w3jn
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« Reply #1 on: December 01, 2006, 08:02:10 AM »

Quote
to possibly save the life of an 833A or mod transformer.

A noble and worthy cause, master Vu.

OTOH the good news is that you're apparently close to gracing us with your on-air presence soon.

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Todd, KA1KAQ
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« Reply #2 on: December 01, 2006, 10:15:09 AM »

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W1ATR
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« Reply #3 on: December 01, 2006, 10:50:19 AM »

ouch. That sucks. I did that once with a 4-1000..
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« Reply #4 on: December 01, 2006, 12:51:22 PM »

Yaz needs to keep his right paw in his pocket soon.
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