Thanks for the advice.
Only tuning of the input circuit left. Then ready for the test.... :)
73's
Ulf (SM0NOR)
ulf@sm0nor.com
On 6 dec 2011, at 19:13, Eddy Swynar wrote:
> Hi Ulf,
>
> Well, I can only speak of my own personal experiences here with a 4 x 811A
> amplifier that I built here some 31 years ago...FWIW!
>
> First-off, I used surplus tubes in mine---so take what I say with a grain of
> salt, or ignore it altogether.
>
> (1) One of the 811As that I purchased had, unknown to me, an internal short
> from the grid to to the filament: the moment I applied power to it, the grid
> meter pegged itself, & I had to get a new one. Lesson learned: check all of
> the electrodes for shorts BEFORE installing the tube.
>
> (2) When I initially attempted to run all 4 tubes under load in the
> amplifier, the very second I hit the key I noticed that the plate of one tube
> would appear redder than the rest---then in seconds it would turn yellow,
> then white, and then a small hole the size of your smallest fingernail would
> appear right in the middle...and a fuse would blow. Lesson learned: MATCH
> each individual tube for resting current. Failure to do so will cause a
> "discrepant" tube to "hog" the load, & it'll self-destruct in short order.
>
> I can't even recall now how many 4-pin coil forms I ended-up getting out of
> that exercise, before I learned the importance of matching tubes for resting
> current! But again, these were all surplus jugs that cost me probably two
> bucks a pop ("pop"---literally!), so the lesson---though still rather
> expensive back then---didn't exactly break the bank...
>
> One more step to do as a precaution might be to "bake" the tubes for an hour,
> or so, with just their filaments on---no plate voltage. I've never done this
> personally, but have read that it's a good idea with surplus stock...
>
> There you go, Ulf---at least ONE taker to your query, so far...
>
> ~73!~ de Eddy VE3CUI - VE3XZ
>
>
>
> *****************************************************************
>
>
> On 2011-12-05, at 5:36 PM, Ulf (SM0NOR) wrote:
>
>> No takers?
>> This ought to be a very simple question :)
>>
>>
>> 73's
>>
>> Ulf (SM0NOR)
>> ulf@sm0nor.com
>>
>>
>>
>> On 4 dec 2011, at 11:23, Ulf (SM0NOR) wrote:
>>
>>> Hi all,
>>>
>>> I recently bought 4 Cetron 811a from Nebraska Surplus, date coded 1988.
>>> I intend to put them into a home brewed amp that is real close to smoke
>>> testing.
>>> Is there any start up procedure that is recommended for NOS 811:a? I have
>>> not come across any recommendation regarding this so far. But before, I put
>>> them in and apply filament and HV, I thought i'd ask here.
>>>
>>> Thanks!
>>>
>>>
>>> 73's
>>>
>>> Ulf (SM0NOR)
>>> ulf@sm0nor.com
>>>
>>>
>>>
>>
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>
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