The melting was occurring inside the pins, not in the wiring of the
socket. I used good high-temperature silver solder to do the resoldering.
Interesting point about the Harbach fan - it certainly makes a lot more
noise, so I figured it must be moving more air. Oh well...
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,
spots at telnet.reversebeacon.net, port 7000 AND now
at arcluster.reversebeacon.net port 7000
On 12/7/2011 12:33 PM, Carl wrote:
> Ive heard that the Harbach fan provides less actual cooling.
>
> A cleaned and lubed original fan, correct placement of the blade and
> the little top plate in place should be all that is required.
>
> Replacing the contacts is a good step as well as using real solder
> with the right temperature rating. Ive also found many 220's with poor
> original soldering that contribute to the initial overheating.
>
> Carl
>
>
> ----- Original Message ----- From: "Pete Smith" <n4zr@contesting.com>
> To: <amps@contesting.com>
> Sent: Wednesday, December 07, 2011 6:48 AM
> Subject: [Amps] SB-220 filament pin cooling was: Re: Replacing 3-500Z
> tubes with 4-400A tubes
>
>
>> I have had recurrent trouble with filament pins coming unsoldered in my
>> SB-220 during heavy contest operation, even though I have the
>> replacement Harbach fan that is supposed to move something like 30% more
>> air. I recall, years ago, reading that a lot of the heating might be
>> due to relatively high resistance between the pins and their socket
>> clips. The same author, if I remember right, also opined that the
>> heating would, over time, cause the clips to lose their temper,
>> aggravating the problem.
>>
>> I went in and swapped two of the grid clips for the filament clips on
>> each socket, polished the pins and the inside of the clips, and put a
>> small fan on top of the tube compartment to help move air through.
>> Haven't melted a filament pin since. Fingers crossed.
>>
>> 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,
>> spots at telnet.reversebeacon.net, port 7000 AND now
>> at arcluster.reversebeacon.net port 7000
>>
>>
>>
>> On 12/6/2011 4:32 PM, Carl wrote:
>>> The SB-220 cools the filament pins.
>>>
>>> Carl
>>> KM1H
>>>
>>>
>>> ----- Original Message -----
>>> From: "Bill Fuqua"<wlfuqu00@uky.edu>
>>> To: "John King"<k5pgw@yahoo.com>;<amps@contesting.com>
>>> Sent: Tuesday, December 06, 2011 9:15 AM
>>> Subject: Re: [Amps] Replacing 3-500Z tubes with 4-400A tubes
>>>
>>>
>>>> One possible issue with the 4-400A is that it has a metal shield
>>>> around
>>>> the glass seals on the base.
>>>> The cross flow cooling used in some amplifiers does not work well
>>>> and an
>>>> additional fan
>>>> may be need to cool the seals.
>>>> Maybe someone can comment on this that have had personal experience
>>>> making the conversion.
>>>> 73
>>>> Bill wa4lav
>>>>
>>>>
>>>>
>>>> At 04:20 PM 12/4/2011 -0500, John King wrote:
>>>>> I have several very good 4-400 A tubes and have replaced a pair of
>>>>> bad
>>>>> 3-500Z tubes with a pair of 4-400A tubes in a Heath SB 220 amp.
>>>>>
>>>>> I have noticed much lower resting current being drawn when keyed
>>>>> up. I
>>>>> have noticed about 200 watts less power output with 100 watts
>>>>> drive. The
>>>>> 4-400A tubes are as new.
>>>>>
>>>>> I made no changes to bias or other parameter adjustment. I would
>>>>> appreciate the benefit of your knowledge and experience regarding
>>>>> the tube
>>>>> substitution. Thanks and 73, John, K5PGW
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>> _______________________________________________
>>>> Amps mailing list
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>>>>
>>>>
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>>>>
>>> _______________________________________________
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>>>
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>
>
>
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