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

[Will Matney <craxd1@ezwv.com>]

Dan,

There grid resistors are there to actually work as a fuse which will 
open if an internal arc in the tube occurs (anode to grid). Most likely 
the resistor had failed some time back and was probably broke or 
cracked. This was making the arc that you seen. Finally the resistor 
gave way and failed completely. I would just change them out with new 
ones on each tube. There's squirlley reasons for this internal arc but I 
wouldn't worry too much about that. The main thing is just replacing the 
resistors with the same size. You will want non-inductive resistors here 
of course. I'd say that this will cure your problem.

Will


Dan wrote:

> 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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