[Amps] 3-500Z pin becomes unsoldered

[Pete Smith N4ZR]

For whatever it is worth, I had this problem frequently in contest 
service, even with the higher-capacity Harbach fan.  Finally, I swapped 
the filament springs for two from the grid, polished the tube pins and 
the insides of the contacts, and have had no problems thereafter.  I 
could have done these things one at a time, but who believes in the 
scientific method anyway?

73, Pete N4ZR
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On 5/14/2014 9:55 AM, Carl wrote:
> That Johnson 122-275 ceramic socket goes back to the 50's when just 
> about everything used expensive Eimac forced air flow cooling and the 
> cast aluminum sockets with chimneys cost more than the tubes. Johnson 
> received an OK from Eimac for horizontal cooling in their 
> 4-250A/4-400A transmitters and amps and other companies followed suit.
>
> The SB-220 cooling is well thought out and sufficient as designed. The 
> problem is builders and other owners who cannot read the manual and 
> dont place the fan blade at the proper point on the shaft and/or leave 
> off that small aluminum air deflector on top of the perforated cover. 
> Failure to clean the blades and lubricate the motor just adds another 
> level of problems.
>
> The socket uses a rivet to assemble the pin and when the tube pin 
> overheats that compression bond is weakened. A cure is to gently 
> compress the pin to original spacing and then use a D-550 or similar 
> gun and a bit of diluted hydrocholric acid, also sold as plumbers 
> soldering fluid, and flow some silver bearing solder to bond it all 
> together. Use a toothbrush and the acid to remove the heat bluing. 
> Flush out the acid residue with a water and baking soda mix in a spray 
> bottle.
>
> Others may be more comfortable replacing the socket (-;
>
> I dont like the Chinese sockets as it is easy to rupture the tube seal 
> especially with the older all glass base without the brown compression 
> ring. Ive heard a few stories of that happening with both versions.
>
> In the hundreds of 3-400/500 amps Ive worked on only a very small 
> number required replacing the socket which were broken by a users 
> brute force attempt to restore tension.
>
> Carl
> KM1H
>
>
>
>
> ----- Original Message ----- From: "Alf Pousar" <alf.pousar at surffi.net>
> To: <Amps at contesting.com>
> Sent: Wednesday, May 14, 2014 4:15 AM
> Subject: [Amps] 3-500Z pin becomes unsoldered
>
>
>> If your solder lugs are dripping the solder due to heath, clean the 
>> lug using a good desolder wick and wrap the wire around and trough 
>> the lug. Then take some small wrapp wire and wrapp around the lug.
>> Then... solder with high temp ten/silver solder and the problem is gone.
>>
>> Alf  OH2QM
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