[Amps] Alpha 76 "SNAP" noise

[John G3UUT]

Thanks for the note Mike and I'm going to do the sensible thing and 
change the lot.  I had the experience of a PSU electrolytic blowing up 
when I was about 16 and don't wish to repeat it, especially as my ticker 
is now a lot older.

73 John G3UUT

On 14/01/2015 11:06, Mike Tubby wrote:
> I suggest that you change the caps and the equalising resistors too!
>
> Our Henry Tempo 2002A started making fizzing and crack noises some 12+ 
> years ago during a contest.  L:uckily at the time I had a spare 
> rectifier + caps + resistors bank which I substituted to keep us on air.
>
> On further investigation we found that the 2W Carbon Composition 
> resistors that were supposed to be 470K were all over the place - 
> anywhere from 470K, 500K, 600K, 900K and one was > 2M - hence the 
> voltages across the caps were not equal and this lead to stress on the 
> caps which could have resulted in an explosion!
>
> There are good quality, high voltage, high current Metal Oxide Film 
> (MOF) resistors which should be considered these days.
>
> Mike G8TIC
>
> On 24/12/2014 02:10, Alek Petkovic wrote:
>> BANG!
>>
>> Yep. They were talking about the electrolytics.
>>
>> Change 'em, before you have to change your underwear.
>>
>> 73, Alek.
>> VK6APK
>>
>> On 24/12/2014 7:59 AM, John G3UUT wrote:
>>> Sorry folks, are we talking about the string of smoothing 
>>> electrolytics or a ceramic RF filter cap here?  I'm curious about 
>>> this as when I switched my 2m amp on recently which hadn't been used 
>>> for about a year there was a regular series of 'snaps', the 
>>> frequency of which gradually diminished as it warmed up.  I was 
>>> worried by this but it didn't seem catastrophic and seemed to be 
>>> improving with time so I left the amp on.  By the end of the contest 
>>> the amp was usable (typical) - I couldn't really use it earlier as 
>>> the snaps put quite a high level pulse of QRM into the RX path.
>>>
>>> 73 John G3UUT
>>>
>>> On 23/12/2014 11:08, Andy Cook, G4PIQ wrote:
>>>> Oh yes. I heard this coming from one of our old Alpha 78s during 
>>>> CQWW CW at 5U5Z some years ago. It did this for quite a few hours 
>>>> and then in the middle of the night there was a big bang and the 
>>>> room filled with smoke as one of the filter caps let go. It 
>>>> certainly woke the operators up. I should change those caps now!
>>>>
>>>> 73
>>>>
>>>> Andy, G4PIQ
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>>>
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>
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