Gentlemen, 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
Author: Felipe Ceglia - PY1NB <felipeceglia2@gmail.com>
Date: Sat, 27 Jun 2009 07:37:56 -0300
Hi Angel, I one recent CQ DL magazine, may 2009 (the one with the CW op YL on cover), there is a project for a funf-tube PL519 amplifier. If I recall it correctly it does not use a HV trafo, but for
Dear Felipe, What a coincidence! I just got this quarter-century old amp with obsolete tubes, and almost at the same time, the CQ DL publies an article about a similar design! About the Fuchskreis: T
ORIGINAL MESSAGE: REPLY: This is an ancient design and was pretty much abandoned years ago for good reason. Take a look at handbooks from the '30s and '40s and you will find it there. There are two m
...if anyone wants to get away from the tested and true PI or PI-l circuits a better choice would be a link coupled tank circuit or a multiband circuit similar with the Z-Match innards. This is exact
A very good point Bill! In this particular amp, plenty of room is available for the tank circuit. I will consider replacing the "Fuchskreis" with a Pi or PI-L circuit. But then there is the problem o
Hi Alex, An interesting idea, but since there is plenty of room in the tank circuit compartment of the amp, I think I will first try replacing the Fuchskreis with a pi-circuit, if the anode impedance
That was done in order to avoid VHF ring oscillation, a common problem with paralleled tubes. They ha d a tendency to oscillate at a frequency set by the tray inductances of the tank circuits and the
Yes, to obtain tha beautiful cherry red glow of the plates :-) a better option would be to increase the plate voltage. With only 600 V from plate to cathode, the cathode current gets too high and the
I see. A sort of push-pull oscillator with the link between the plate of two tubes acting as an inductance. Therefore you try to keep this inductance low by using sheet metal instead of wire. Resonan
Kudos to CQ-DL! I e-mailed them yesterday to buy a copy of the May 2009 issue of CQ-DL Magazine . Instead I found this morning in my mailbox an e-mail with a pdf of the article - no charge! Many than
ORIGINAL MESSAGE: REPLY: Sweep tubes are not intended to run with any color on the plates. If you need more output, bet a bigger tube. I did TV repair for nearly 20 years back in the tube era. A glow