On Nov 6, 2006, at 4:36 PM, pentalab wrote:
--- In ham_amplifiers@..., Jan Erik Holm <sm2ekm@...>
wrote:
I?m working on fixing up a L-4B, it has fried resistors
in the supressors. They use 3 x 15 ohms but I have none
in my junkbox however I have plenty of 10 ohm R?s, will
that do? 3 x 10 ohm R?s?
It doesn?t seem to matter too much, I notice that the L-7
use 2 x 47 ohm R?s
### Whoa.. stop right there. I Don't have the L4B manual handy...
but I'm positive they use 2 x 47 ohm 2 Watt carbon resistors.. and
silver plated strap..... should be same or similar to the L7. I'll
check all 4 x of my L4B's later tonight.
A timely question: Why did the resistors fry?
and the Henry 3K 2 x 150 ohm R?s, it
seems to be all over the place.
I?m following VE7RF?s advice to ground grid pins with
wide straps.
#### Originally when I tried this stunt.. I used just one strap ,
from just ONE grid pin PER socket.. [2 x straps in total]. Worked
good... except 10m input swr went nuts. ...
Suppose I have to put in a fuse in the B-
return to be safe.
### IF u want a high speed grid fuse.... install a 3agc bayonet
type fuse holder on rear panel. Wire between grid shunt and
chassis. [stock, one end of grid shunt goes to chassis... just open
this point up] Use a 250-350 ma fast fuse.
Also I?m swapping out the .82 R in
the PS for a better glitch R,
#### Whoa. The .82 R 1 watt resistor in the B+ ... IS the HV
fuse ..
It's not a HV fuse because a metal vapor arc forms between the
resistor's two copper wires as the fuse disintegrates. Current stops
after the arc extinguishes - and that only happens after the filter
caps have mostly discharged.
Real HV fuses are lengthy and they are filled with silica sand to
extinguish the metal vapor arc. However, since a HV fuse does not
limit initial peak current, one needs a sturdy glitch-R.
NOT a glitch R. LEAVE the .82 ohm IN !
That's an order!
### Here's where u install a glitch R in a L4B. ...
...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org
