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Author Topic: Cleaning Pins on Eimac 3CX1500A7  (Read 2247 times)
K9ZM
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Posts: 13




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« on: September 10, 2011, 07:19:30 PM »

Had a used 8877 arrive today and it appeared to be dead when tested in my Henry 3KD premier 8877 amp.  Checked for continuity on the heater and it's not open.  The cathodes are common.  At least on the pin bases.  But when touching the pins I could not get continuity at all times.  It's like there is something on the pins preventing contact.  But all I can see is that matt finish Eimac uses.  And marks from insertion into a tube socket.

What is the best and safest way to clean ceramic tube pins?

73
Greg k9zm
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WB2WIK
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« Reply #1 on: September 10, 2011, 07:44:19 PM »

I think this is very unusual.  I have 25 year old 8877s whose pin contact surfaces are just fine.

If I were to clean them I'd just use a Scotchbrite pad.  But normally this doesn't happen.
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ZL4IV
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« Reply #2 on: September 10, 2011, 09:45:45 PM »

I had the same problem with a GU78B. Genital rub with Scotchbrite did the trick.
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K1ZJH
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« Reply #3 on: September 10, 2011, 10:48:57 PM »

I had the same problem with a GU78B. Genital rub with Scotchbrite did the trick.

Ouch!!! Sounds painful too me. I'll pass.
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W8JI
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« Reply #4 on: September 11, 2011, 02:41:40 AM »

Personally, I wouldn't clean them with scotchbrite.

They are silver plated. If there is any film blocking conduction it has to be a very thin layer. I'd either rub them with an eraser soaked in WD40 or a solvent, or use a nonabrasive silver polish for silverware.

Whatever you do, let us know how it works. I've never yet seen a pin connection issue with an 8877, although I have seen several intermittent filaments.
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AB4D
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« Reply #5 on: September 11, 2011, 06:43:47 AM »

I had the same problem with a GU78B. Genital rub with Scotchbrite did the trick.

Ouch!!! Sounds painful too me. I'll pass.


I think I will pass too!  Shocked

Nevertheless, I would think just a little polishing of the pins with a paper towel would be sufficient.
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K9ZM
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« Reply #6 on: September 11, 2011, 06:50:36 AM »

Thanks all.  I suspected to go carefully and you fellows confirm that.  I will let you all know how it turns out.
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K9ZM
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« Reply #7 on: September 11, 2011, 08:04:55 AM »

The tube is still DOA. 

Made a difference cleaning it.  I have solid continuity between all contact surfaces and pins as they should be.  Pins 1 and 5.  And Pins 2, 3, 4, 6, & 7.  I also cleaned the outside of the cooling fins and the ring at the bottom of the tube.  Got lots of residue on the paper towels.  It was described as having been in a corrosive environment.

I used Nevr-Dull magic wadding polish carefully.  Wiped everything down with clean paper towel.  Then Caig Deoxit D5.  Wiped everything down again with a clean paper towel. 

My FT-2000D sees a nearly 3.0 SWR with this tube in line.  So I honestly do not know what is wrong with it.  But I cannot get any power though it.  So back to the original tube. 

Thanks gents!

73
Greg k9zm
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