GS-35B Triode
Grounded Grid Linear Amplifier Project
For Amateur Radio by W4ZT
(Latest
update done on July 6, 2008)
WARNING!
DANGER! HIGH VOLTAGE!
This project uses dangerous high voltages.
These voltages will not just shock you, they will kill you.
Use extreme caution while building, working on and testing.
Always THINKSAFETY! Only YOU can prevent accidents.
Tony's first rule for tubes:
Tubes are like women... If you feel that you must have two, keep them in separate houses, and don't let them know about each other. If one isn't good enough for you, get a better one.
In other words, if one tube isn't enough for you, don't run two, get a bigger tube!
The next logical step above a single GS-35B isn't two of them... it is a single YC-156
Pozy's first rule for building home brew amplifiers (http://k4poz.w4zt.com):
"If your
amp is going to require more than 100 Watts of drive, you need to get a different tube."
My Own Links and General Amp Information:
W4ZT Socket - This is my GS-35B tube socket or mounting fixture design. It virtually eliminates the stray inductance in the grid circuit. Click on the picture to see the details of the construction. The socket to the right has my *Teflon® Chimney in place.
I make and sell Sockets, PTFE Chimneys and Bias Boards:
CAUTION: I have documented proof that there is a problem using PVC as a chimney. CLICK HERE for pictures and more information.
Tube Tester and Filament Burn In Jig - Here's my answer to cooking the tubes for days and then testing them before inserting them in an amp. Note - I have learned an important lesson with this jig. The filament alone heats the entire bottom of this tube and even with the fan blowing air into the box, the bottom of the tube will get too hot to hold in your hand. This is an important lesson regarding cooling of the tube, particularly the grid ring and filament seals.
Do NOT run this tube without air, lots of air, blowing around its base and through the anode cooler. There is 38 watts of heat from the filament alone. W4ZT
GS-35B Tubes Glow In The Dark! - Pictures of GS-35Bs glowing in the dark producing a rainbow of color. Do yours glow? My bet is that they do. What color are they? Want to share your pictures?
Schematic of the GS-35B Amp - An effective simple schematic.
NOTE: Do NOT use a center tap filament transformer. To do so leads to unbalanced currents in the filament choke and hum modulation of the RF output. Instead, use a separate cathode choke. Note that the filament choke can be made with two 48" long pieces of #18 wire bifilar wound to fit on a 3.5" length of 3/8" ferrite rod. The cathode choke can be one 48" length of #18 wire on a 1.5" length of 3/8" ferrite rod. Both chokes are about 25 to 30 uH. Be careful to wind the chokes on a metal rod slightly smaller than the ferrite and then move them to the ferrite rod to prevent breaking the ferrite.
Show and Tell GS-35B Amp - built big and open to show everything inside except the cathode compartment. A work in progress.
Max-Gain Systems - Allen Bond has Vacuum Relays, Vacuum Variable Capacitors, Turns Counters, Fiberglass and many other hard to find RF Transmitting Components. High quality components and the best service: http://www.mgs4u.com
QRO-Parts.com - GS-35B Tubes via Texas or direct
Nice new old stock tubes in the foam box available at reasonable prices plus shipping charges from Russia. He also has the GI-7B, a large selection of vacuum variable caps, vacuum relays and other parts for the QRO builder.
Payment and shipping can be made in the U.S. via storage in Texas.
http://qro-parts.com/
Almost All Digital Electronics L/C Meter - If you are going to be building an amp, this tool is invaluable. You need to be able to know what value your capacitors and inductors are and to be able to wind coils as needed:
http://aade.com/lcmeter.htm
KD9JQ - Ham Radio Page for Homebrewers
Was at this address http://mywebpages.comcast.net/kd9jq/hamradio/kd9jq.html but Chuck changed his ISP to MSN. MSN wants you to sign up to view his pages so they are no longer available by direct link. You can still view this page by using the Wayback Machine at http://archive.org which will take you here: http://web.archive.org/web/*/http://mywebpages.comcast.net/kd9jq/hamradio/kd9jq.html
AG6K - Rich has lots of amp building info on his site. Years of experience and knowledge to share. See the pictures of the ugly amps, etc. There's a great multi-part article on amplifiers that he put together for the ARRL Handbook. Read, if you dare, about Richard Measures' clash with ARRL over his writing about amps, advertiser control of QST and other interesting stuff. (W4BD) http://www.somis.org/
F1FRV - Dominique has nice logic, control and metering circuits and cards and lots of other amplifier info including pi-networks and testing of tubes. Main page - http://f1frv.free.fr (click on Linear Amps)
Other than by band, these links are provided in no particular order. Thanks to everyone for your links!
(click on the links or the pictures for more information)
HF
Amps:
Schematic of the GS-35B Amp - An effective simple schematic.
NOTE: Do NOT use a center tap filament transformer. To do so leads to unbalanced currents in the filament choke and hum modulation of the RF output. Instead, use a separate cathode choke. Note that the filament choke can be made with two 48" long pieces of #18 wire bifilar wound to fit on a 3.5" length of 3/8" ferrite rod. The cathode choke can be one 48" length of #18 wire on a 1.5" length of 3/8" ferrite rod. Both chokes are about 25 to 30 uH. Be careful to wind the chokes on a metal rod slightly smaller than the ferrite and then move them to the ferrite rod to prevent breaking the ferrite.
Show and Tell GS-35B Amp - built big and open to show everything inside except the cathode compartment. A work in progress.
eHam.net
- Other hams review
the GS-35B. W2APE swaps out an 8877 with a GS-35B in his Harris
AM-7224/URC. After a few changes he is highly pleased with the
update:
WB8WJU
- Tom has built many GS-35B amps and has lots of pictures and
info on his site. He's always very helpful. He also sells a socket
for the GS-35B: http://home.comcast.net/~wb8wju/
Challenger
Amp - Note the
construction in the commercially built GS-35B amplifier. See the
under chassis view showing the tuned input (see the link on the
discussion page at my site too): http://www.lauk.karoo.net/hf_amps.htm
F1FRV
- Dominique has nice logic, control and metering circuits and
cards and lots of other amplifier info including pi-networks and testing of tubes. Main
page - http://f1frv.free.fr (click
on Linear Amps)
I5UXJ
- Taking the GS-35B to high levels, this 3 tube amp delivers 6000
watts output with 250 watts drive. Just goes to show you what
can be done if you're into it! See it at: http://i5uxj-2.cln.it/amp/amphf1/amp1.html
*Teflon®
is PolyTetraFluoroEthylene (PTFE)
PTFE is a fluorocarbon-based polymer. It is commonly called Teflon®
which is the registered trademark of DuPont. PTFE is also manufactured by
other companies. It is available with or without filler materials to meet
specific needs. The PTFE used here has no fillers and is called "virgin
PTFE".
Spammers,
please add these addresses to your list as they need all the email
they can get (they are known to send spam email themselves:
- dbirdsley@tds.netinfo@hamthreads.com
WARNING!
DANGER! HIGH VOLTAGE!
Your safety is YOUR responsibility. The information provided
here is for information purposes only. No liability is assumed
by providing you with this information.
Please work safely.
If you don't feel safe, step back and avoid the danger.
Don't
work on this kind of project while you are tired.
Don't
work alone.
Don't
work with the power on!
Remember,
capacitors store energy and they can deliver a dangerous shock
long after the primary power source has been removed. Keep
one hand in your pocket.
Better still, keep BOTH hands in your pockets :~)
This page
was started February 11, 2004 and the last update was on July 6, 2008.
- This is my GS-35B tube socket or mounting fixture design. It virtually eliminates the stray inductance in the grid circuit. Click on the picture to see the details of the construction. The socket to the right has my 
