re: follow up and opinion comments about the Dentron
GLA-1000 and similar amplifiers. (like the Amp Supply
LA-1000)
-
[snip]
: From: "Tom Rauch" <w8ji@contesting.com>
: To: "carl seyersdahl" <carlseye@tampabay.rr.com>
> thing. The others are out of line if they think a plain
> model or even a "B" model is worth much.
-
: Let's think about it.
: 1.) You can not easily get tubes any longer
-
I don't agree. Tubes are easy to find, the cost is another
issue. The last low dollar tube cost (1 year ago) quote
was about $20 per tube. That source quickly sold out..
Others can be found with a little digging around on
the net and through the news groups. Regular retail
price is about $40 to $75 per tube.
-
: 2.) The amps are terribly unstable on ten meters
: because the "designer" directly copied the Bill Orr
: Handbook where the cathodes are tied to the control
: grids.
-
Close but not exact. Bill Orr included cathode current
reduction in the standby/receive mode. The #1 control
grid to cathode connection is nothing new, I've not
heard of or seen information / proof of it being an issue
with 10 meter stability. Not my personal cup of tea
circuit layout for this tube, but it's easy enough to fix
with something that works well.
-
Only certain tube geometries allow this type of cathode
grid connection. The obvious statement is that the
designer and the operator must pay attention to the
details. It is an amplifier in family of very low duty
cycle types... many models and similar brands were
sold through the years.
-
: 3.) The tuned inputs and tanks were virtually never right.
-
A few examples were not even in the same ball park.
People doing the Svetlana EL-509/519 retrofit find out
the hard way that it's not all just plug and play. But an
evening with some tools and the proper information
(via a handbook & calculator) can get the tuned circuits
back in line.
-
: 4.) You can't get some of the small parts like
: electrolytics any longer, so you have to patch in
: other parts that don't quite fit.
-
Not exclusive to the Dentron... In general, most all
electrolytics have changed in size/value relationships.
-
The mighty Heathkit Amplifiers have the same issue,
were it not for the Harbach units many would be asking
the "where and what" question so often that a rubber
stamp answer would be in order. FAR Circuits has
a replacement set of pc boards along the harbach
lines that deals with the power supply cap issues.
-
: 5.) They were only 400 watt amplifiers with generally
: short tube life anyway.
-
Excessive heat kills them very fast. Other than that,
you can expect decades of regular service as I have
received. Most mfgrs of similar amplifiers rated their
operation at 600 watts @ max drive. Some pushed
the envelope label to 1k input.... on a good day with
a tail wind maybe. It's not realistic...
A glass tube supplier told me a few years ago,
these types of tubes are given thousands of hours
of rated operation as an estimate of normal tube
life. I've had tube TV sets with thousands of hours
operation on the same 6LQ6 before the TV went
away. I have many sweep amplifiers from the
70's & 80's with the same original tubes on board.
They still provide normal output.
-
: Outside of collector demand, it seems to me they are
: worth nearly zero dollars
: 73, Tom W8JI
-
Just depends on your point of view, budget and how
handy you are. As a project amplifier, they are cheap
enough for a first repair/rebuilt/starter amplifier. I've
seen the Svetlana tubes and have a picture from an
Italian Amateur (Bernie) with a pair of 4cx250's in the
same space/cab.
-
With 40 watts drive, an improved Dentron or similar
Amplifier could provide 10dB or more, stage gain.
Nothing wrong with an extra 10dB... You can't buy
the parts to use as a starter amplifier project for what
you can pick up a dead Dentron for...
-
The proof of what they often sell for is available on
Ebay most any day.
-
cheers
skipp
-
(Making plans to again see everyone in Dayton)
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
http://dl.www.juno.com/get/web/.
|