[Amps] 3-500 filament meltdowns was: Re: Centurion plate current issue

[Carl]

When the clips are hot enough to melt solder the metal has become annealed. 
Wire brushing until the original nickel plate appearance is restored works 
as long as the clip still can apply pressure on the tube pin. Swapping with 
a grid is a good alternative.

Carl
KM1H


----- Original Message ----- 
From: "Pete Smith" <n4zr at contesting.com>
To: <amps at contesting.com>
Sent: Thursday, June 10, 2010 4:36 PM
Subject: [Amps] 3-500 filament meltdowns was: Re: Centurion plate current 
issue


> My SB-220 has had this problem for some time.  I resoldered the pins on
> at least 3 3-500Zs using silver solder from AG6K, and then finally
> swapped two of the grid clips on each socket for the filament clips, on
> the assumption that perhaps the spring steel had lost its mojo through
> long-term heating.  Whatever, I haven't melted one out since, so it
> might be worth a try if your sockets permit it.
>
> 73, Pete N4ZR
>
> The World Contest Station Database, updated daily at 
> www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net, blog at 
> reversebeacon.blogspot.com
>
>
> On 6/10/2010 1:53 PM, Patrick Barthelow wrote:
>> Have heard of the solder melting and dripping away on filament pins. 
>> Probably good thing, to use as a flag warning of cooling problems, or 
>> heavy abuse of the amp, suggesting attention to more cooling reqts, for 
>> your particular installation.   Dont know if the original pins that were 
>> susceptible to melting (with abuse) was a low temp solder, (like 60/40) 
>> or higer temp, (silver) alloy.  In any event, the melting solder pin 
>> should not consdered to be too bad, kind of like a Canary in a mine, 
>> whose failure signals a deeper problem.
>>
>>
>>
>> One cause of pin solder melting that I have heard about is cheap 
>> imitation sockets, that do not have a heavy grip on the tube pin, will 
>> cause excessive heat due to the 15 or so amps carried to the filament, 
>> dropping watts at the clip.
>>
>>
>>
>> Just another note, especially with the ceramic 3-500Z sockets, with very 
>> firm gripping clips, is to carefully push the tube STRAIGHT DOWN into the 
>> socket rather than taking the seemingly easier route of rocking the tube 
>> and pins, side to side which can easily destroy the tube.  I wonder if 
>> some sillcone grease lube  applied sparingly to the pins before insertion 
>> might make the insertion less nerve wracking, and still not interfere 
>> with adding resistance to the connection.
>> Best Regards,
>> 73, de Pat Barthelow AA6EG
>>
>>
>>> From: dezrat1242 at yahoo.com
>>> To: amps at contesting.com
>>> Date: Thu, 10 Jun 2010 10:07:50 -0700
>>> Subject: Re: [Amps] Centurion plate current issue
>>>
>>> ORIGINAL MESSAGE:
>>>
>>> On Thu, 10 Jun 2010 07:47:43 +0800, Alek Petkovic<vk6apk at bigpond.com>
>>> wrote:
>>>
>>>
>>>> I believe all current production 3-500Z tubes, apart from Amperex,
>>>> are made in China so it won't matter much which sort you buy.
>>>>
>>> REPLY:
>>>
>>> I heard not long ago that one brand of 3-500Z has solid filament pins
>>> as opposed to hollow pins that are soldered. If that is true, I would
>>> recommend buying that brand if you can find it. Soldered pins are
>>> notorious for un-soldering themselves over a period of time.
>>>
>>> If anyone has the facts on this, please post.
>>>
>>> 73, Bill W6WRT
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>>>
>>
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