----------
From: richard w. ehrhorn[SMTP:w4eto@rmii.com]
Sent: Monday, December 08, 1997 2:46 PM
To: 'amps@contesting.com'; 'km1h @ juno.com'; 'Rich Measures'
Subject: RE: [AMPS] smoked TL922
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From: Rich Measures[SMTP:measures@vc.net]
Sent: Monday, December 08, 1997 11:38 AM
To: km1h @ juno.com; amps@contesting.com
Subject: Re: [AMPS] smoked TL922
>
>On Sun, 7 Dec 97 17:31:47 -0800 Rich Measures <measures@vc.net> writes:
>>>
>>>On Sun, 7 Dec 1997 11:26:57 EST JW KIMBALL <JWKIMBALL@aol.com>
......snip...
>>>Sounds like a simple case of internal arcing in the tube. A 10-20 Ohm
>>>resistor in the HV lead would possibly have minimized the damage.
>>>The grid chokes are also way too large in current capacity. Replace with
>>>150-200 ma types which have both extra resistance to provide a bit of
>>>degeneration and will act better as current absorbers.
>>>
>>Chokes make flaky fuses. Ordinary carbon film resistors are easier to
>>blow than chokes, and they are cheaper. Fast-acting 0.25A 250v fuses
>>would probably work.
>
>Are you suggesting he actually drill 2 holes on the rear apron for fuse
>holders ???????
I would solder the fast-acting 0.25A 250v fuses between the grid pins and
chassis ground. .
>Seems you were bitchin' about a similar suggestion last week.
The suggestion of mounting grid fuses on the rear panel was not mine.
>In any cases fuses should be in some easily and quickly accessible location.
>Personally, I prefer the chokes since as current absorbers of minor arcs
>from gas, etc they will not blow or collapse. Once the event has passed
>the amp works as before.
>
It might be interesting to high-pot such a tube immediately after the
suspected gas arc, just to see whether the tube is gassy or not -- unless
you subscribe to the rauchian vanishing gas theorum. .
#####
It definitely is true that in the vast majority of cases, after one or two
BANGs early in life, the tube continues on for a normal lifetime of
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