[AMPS] GLA-1000 work

[skipp isaham]

Hi Carl, 
-
: A friend of mine has a gla1000 ,plain model, which has 
: been modified to use el509's. 
-
How? just the physical replacement of the original 
tubes with the EL-509's..?  ... or was the more complete 
job done (cathode current cutoff in standby, parasitic and 
tuned circuit values reworked with optimum values 
required by the new tubes types)..? 
-
: He states that 15 and 10  meters has no gain at all. 
-
Reduced output is not a desired product of a 
conversion.
- 
: I have questioned him extensively on it, input filter, 
: pi-net changes, etc. per the Svetlana mod. article, 
-
I have found problems with the Svetlana Article and 
I consider it incomplete (doesn't contain the easy to 
add standby cathode current cutoff circuit and has 
other shortfalls).  
-
I have considered calling a few incomplete Conversion 
Articles - Modifications "to the carpet" because I feel 
they have serious short comings and/or errors. 
- 
But I've seen the grief Rich went through over his 
QST Text and decided a prolonged argument with 
entrenched mule heads is not worth my time. The 
Net provides an idea forum to present information 
and opinions, so I put what I can into web pages. 
- 
: but no output except what is feeding thru. (100 
watts input). 
- 
100 watts drive is way to much... 60 to 80 watts max 
drive produces mucho betta' linear operation. I run 
mine a 40 to 60 watts input and my similar type 
amplifier preforms very well. 
-
: he states that the lower bands work fine. 500 or so 
: watts out with about 65 watts in. 
-
Because (percentage wise) the input/output L&C 
Values are less out of wack from what should be 
their proper design values.  The original circuits 
provide a measure of  "fudge values" which work 
better on the lower HF bands.
The suppressors should also be replaced, L-sup 
reduced quite a bit adjacent to the classic 100ohm, 
3 watt low L-int resistor. 
- 
: he and I have been over this thing in detail and have
: not found anything beyond , in my opinion, some 
: fault in the pi-net, but he has said that it was 
: checked both with an mfj analyzer and with a grid
: dipper, and all seems to be tuning normally. does 
: anyone here have any thoughts to share on this 
: one????  thanks!!!   carl / kz5ca
-
Rework the input and output L&C values as 
required. Install modern suppressors and the 
standby cathode current cutoff as described in 
my Dentron GLA-1000 text available on the sonic 
server. Replace the plate blocking capacitors with 
proper type/value units. 
-
The early GLA and other amplifiers lacking any 
tuned input hardware can be retrofit with ckt boards 
sold by various vendors.  I shy away from anything 
pre built unless it's already set up for my specific 
type and amount of tubes...  ie the values required. 
- 
In a more practical sense, it's not a bad idea to 
"lift" the early Alpha 374 broadband input ckt for 
this early model Dentron. Credit where due, it's a 
nifty circuit approach for this specific type of 
roadblock. 
- 
hope that helps you with Bill's amplifier..
cheers
skipp
nospam4me@juno.com 

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