[Amps] ok ONE more time <g> Ameritron 811H

[R.Measures]

On Jan 3, 2005, at 4:37 PM, Dan wrote:

> Got it and thanks for all the help!!
> I found the problem with the tube.
>
> right under the tube cap there is a wire coming down and routing 
> around the filaments. on the top (inside) the tube there are two small 
> "springs" for lack of a better term. On the good tubes (all 3) these 
> two springs are sitting down on the tube structure inside the tube 
> missing the wire from the tube cap by at least 1/8 inch or more.

Arcing 1/8" in a vacuum is typically takes way over 15kV.

> On the "bad" tube one of these springs is out of postion poped up and 
> actually touching the cap's wire..

Filament spring displacement is a common result of parasitic 
oscillation since the large burst of I-grid and I-cathode puts a 
lateral E-M-force on the filament.

Things are rarely as simple as they first look.
>
> anyway have new tubes on roder thanks for the help..
>
>
> *********** REPLY SEPARATOR  ***********
>
> On 01/03/2005 at 12:26 PM Charlie wrote:
>
>> Sounds like good troubleshooting technique to me. Maybe you can 
>> evaluate
>> the
>> tube further to isolate what is wrong with it.
>>
>> Charlie
>> Ham Radio - AD5TH
>> www.ad5th.com
>> Live Blues Music
>> www.492acousticblues.com
>>
>>
>>
>>
>> ----- Original Message -----
>> From: "Dan" <dpipes at earthlink.net>
>> To: <Amps at contesting.com>
>> Sent: Monday, January 03, 2005 11:05 AM
>> Subject: Re[2]: [Amps] ok ONE more time <g> Ameritron 811H
>>
>>
>> well thanks to everyone's help I think I have it fixed.. well not 
>> fixed
>> but
>> at least found the problem.  I replaced the 51 ohm resistor a second 
>> time.
>> this time at the advice of a local buddy he said pull that tube that 
>> that
>> resistor is tied to and try again. well pull the tube turned the amp 
>> on
>> and
>> all powers up without the excieing bang/pop.. and flash <g>
>>
>> I did not try to load withonly 3 tubes  but seems that proves the 
>> problem
>> is
>> with the tube.. I have ordered a set as stated earlier and will have 3
>> extras i guess ..
>> any comments about this "test"..
>>
>> thanks
>>
>> *********** REPLY SEPARATOR  ***********
>>
>> On 01/03/2005 at 7:36 AM carl seyersdahl wrote:
>>
>>> The grid resistors are shown in my 811H manual as R 19 thru R22.they 
>>> are
>>> listed as 51 ohms, 2 watt metal oxide.
>>>  I have always replaced these with 33 ohms 1/2 watt , and I've never 
>>> had
>>> any problems, but then I've always replaced the parasitic 
>>> suppressors with
>>> Mr. Measure's
>>>  Nichrome (not microbe) types. Never had any more trouble that I know
>>> of.!!!!!
>>>   carl / kz5ca
>>> ----- Original Message -----
>>> From: "Dan" <dpipes at earthlink.net>
>>> To: <Amps at contesting.com>
>>> Sent: Sunday, January 02, 2005 6:16 PM
>>> Subject: [Amps] ok ONE more time <g> Ameritron 811H
>>>
>>>
>>> You guys have had the answer everytime so far. I bought a 2nd hand
>>> Ameritron
>>> 811H amp. It has worked very well exept .. at first start up serveral
>> weeks
>>> ago.. after it had been stored when i first turned it on it arec at 
>>> the
>>> vents 9right side) switched it off.. long story short after a few 
>>> turn ons
>>> and off it work great.. I get good ooutpit and great reports. Well 
>>> over
>> the
>>> past few weeks once in a while (only when I turn it on) I woud get 
>>> an arc
>>> same place. after it has been on and after serveral times on and off
>> during
>>> the day it would be fine great output and no arc even when switched 
>>> back
>> on
>>> .. seemed like only would do it after it had been off all night and 
>>> then
>>> only sometimes.. I have remoed and check for any signs of arc etc 
>>> never
>>> found anythign..
>>> Well until today.. I switched it on.. and again a little arc that was
>>> visable at the vents..  and quickly this time a loud pop.
>>>
>>> Well obviously not a good thing. I remove the cover again and this 
>>> time
>>> found that one of the 53 ohm 2 watt resistors had actuall blew apart.
>> onone
>>> end. I shoudl mention that this time I had very little power out 
>>> after the
>>> arc/bang..
>>>
>>> In reviewing the circuit I can ot tell what these four resistors are 
>>> but I
>>> assume it has to do with some type of bleeder circuit to grd as all 
>>> four
>>> have one log to grd the other to a small wire maybe 18 ga. (light 
>>> wires..
>>> one is yellow one is blue and the other two are red..
>>> the yellow one is the one that blew the resistor...
>>>
>>> The diagram they provide in the book and the parts list has to be
>>> incomplete
>>> as the 53 ohn resitors are nto even liosted. there are two 
>>> physically near
>>> the rear of the tube cage (just to the rear to the torrid) the other 
>>> two
>>> are
>>> near the front edge of the same are... the yellow wired resistor 
>>> that blew
>>> is one of the two at the rear side of the tube cage..
>>>
>>> Any ideas? Are these bleeder circuits ? part of the neutralization
>> circuit?
>>> .. Any ideas what might of caused this .. this amp sat for about 3 
>>> yrs in
>> a
>>> closet not used.. before I got it..
>>> any ideas woud be of help. Could a tube of caused it? what else 
>>> shoudl I
>>> check thanks
>>>
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>>
>>
>>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org