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[Amps] Sweep tube amp by DL9AH, made by HB9AWI

Subject: [Amps] Sweep tube amp by DL9AH, made by HB9AWI
From: Angel Vilaseca <>
Date: Fri, 26 Jun 2009 22:28:51 +0200
List-post: <">>

I just bought an old amp that uses 5 PL 519 TV sweep tubes in parallel.
As it reads on the box, it was home made on June 1983 by HB9 AWI.
The amp does not work anymore, but it is superbly built. The builder, 
HB9AWI, obviously put a lot of effort into it.

I would like to restore it. It is so well made and so typical of ham 
state of the art at the end of last Century.
No inexpensive Russian power tubes were obtainable at these cold war 
times! On the other hand, old color TV sets with sweep tubes still alive 
were plentiful. The PL519 had the reputation of being quite rugged. Most 
frequently, it was the line output power treansformer of the TV set that 
failed, not the tube.

Unfortunately, there was no schematic included with the amp..

The seller told me the design of the circuit was by DL9AH. It is quite a 
non-typical design:
For one, the tank circuit is not a Pi, nor a Pi-L! It is called a 
Fuchkreis. It seems it was invented by an Austrian ham called Fuchs. I 
never saw anything like it.
The power supply is a transformerless design. Apparently, it delivers + 
and - 300 Volts. So needless to say, the cathode circuit of the five 
PL519s is quite unconventional too. The bias circuit uses two pentodes, 
a PL 504 (a b&w TV sweep tube) and a smaller one. Never saw anything 
like this either!
There is a separate 10-turn potentiometer for each PL519 to adjust the 
current through each tube. Quite sensible when you use five second-hand 
tubes, that may have already lived a number of years as sweep tubes in 
The power supply, the bias circuit, the relays circuit all have lots of 
VK200s and decoupling caps everywhere.

As I just said, in a true ham spirit, it may use cheap tubes, but 
obviously a lot of care was used to design and build this piece of 

So, really, I would like to restore it. I tried finding the DL9AH design 
on the web, but no luck!

Does the phrase " Sweep tube amp, DL9AH design" ring a bell? Especially 
for european hams?

Any information about the design, or schematic welcome.

Vy 73

Angel Vilaseca HB9SLV

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