[R-390] Arcing in 25Z5Ws

[Bob Camp]

Hi

My vote would be to do the solid state conversion. It reduces the heat  
in the radio, improves performance, and costs a *lot* less money than  
the tubes.

Bob


On Feb 17, 2008, at 12:19 PM, Dennis Wade wrote:

> Well it sounds like I just got unlucky with NOS tubes, with the
> possibility of filter caps going south.
>
> In any event, I'm in need of at least 2 good 26Z5Ws.  Anybody have  
> any?
>
> Looking at the going prices....I'm wondering if it isn't time to
> convert to solid state.
>
> Thank you all for your replies
>
> On Feb 17, 2008 6:46 AM, Bob Camp <ham at cq.nu> wrote:
>> Hi
>>
>> The tubes are *rated* for much higher voltages than they are likely  
>> to
>> see with any rational line voltage. That's not to say that 40+ year
>> old tubes aren't a little gassy ...
>>
>> Bob
>>
>>
>> On Feb 17, 2008, at 8:54 AM, Jim M. wrote:
>>
>>> Could this be caused by higher than normal line voltages?  This
>>> happened to
>>> me on a newly purchased radio several years ago.  I concluded the
>>> higher
>>> line voltages today was a cause.  Radio was designed for 115,  
>>> today's
>>> voltages can go over 120 depending on circumstances, putting added
>>> stress on
>>> the tubes and other components.  I now have diodes and a high  
>>> wattage
>>> dropping resistor in the power supply.  Jim N4BE
>>>
>>> -----Original Message-----
>>> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net
>>> ]
>>> On Behalf Of Dennis Wade
>>> Sent: Sunday, February 17, 2008 2:51 AM
>>> To: R-390 HF Receiver List
>>> Subject: Re: [R-390] Arcing in 25Z5Ws
>>>
>>> First of all...please pardon the typo...I do know they're really
>>> 26Z5Ws  :)
>>>
>>> Both replacement tubes were supposedly NOS...how unusual would it be
>>> to find a shorted tube NOS (although they were packed in 6/62).
>>>
>>>        Dennis
>>>
>>> On Feb 16, 2008 7:00 PM, Bob Camp <ham at cq.nu> wrote:
>>>> Hi
>>>>
>>>> My *guess* is that you have a filament to cathode short in the  
>>>> '"bad"
>>>> tube.
>>>>
>>>> Bob
>>>>
>>>>
>>>>
>>>> On Feb 16, 2008, at 9:22 PM, Dennis Wade wrote:
>>>>
>>>>> Good evening all,
>>>>>
>>>>>          Recently I flipped the power on to my trusty Motorola
>>>>> R-390A, and instead of the comforting sound of HF radio, I hear
>>>>> nothing, and see a couple of blue-white flashes.  Because I all  
>>>>> the
>>>>> covers were on and where I was standing, I couldn't see just where
>>>>> the
>>>>> flashes came from.  When looked at the fuses, the 1/4A B+ fuse was
>>>>> blown.
>>>>>
>>>>>           After a brief detour to replace a cracked fuse holder  
>>>>> and
>>>>> a physical inspection, I replaced the B+ fuse and flipped her on
>>>>> again.  Nothing.  The main 3A fuse went too.  Replace that.  Now  
>>>>> it
>>>>> lighted up, but no sound.  All the fuses held too.
>>>>>
>>>>>            Now I pay more attention to what's lit and what's not.
>>>>> I noticed both 25Z5s were dark, and after flipping it off again,
>>>>> cold.
>>>>> Replaced both.  Now one is lit, but not the other.  Swap
>>>>> tubes...same
>>>>> tube is lit in the other position, and now the tube starts to arc
>>>>> inside.  Hear a 60 (120?) cycle buzz now too, but nothing else.
>>>>> Turn
>>>>> power off quickly.  Fuses all held.
>>>>>
>>>>>            Anybody have a guess as to what's going on?  Do I just
>>>>> have some bad rectifiers, or has something else gone south and
>>>>> taking
>>>>> the rectifiers with it.  I'd rather not feed it rectifiers if
>>>>> they're
>>>>> not bad to begin with.
>>>>>
>>>>>                Opinions welcome.
>>>>>
>>>>>                Thanks!
>>>>>
>>>>>                   Dennis
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Dennis L. Wade
>>>>> KG6ZI
>>>>> Carmichael, CA
>>>>> _____________________________________________________________
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>>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Dennis L. Wade
>>> KG6ZI
>>> Carmichael, CA
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>>
>>
>
>
>
> -- 
> Dennis L. Wade
> KG6ZI
> Carmichael, CA
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