Gonset linear amplifiers

[K3ZW]

I need some info about Gonset linears. 

Do the GSB101 & GSB201 use the same plate transformer ??

They both ran four 811A's. Looking at pics on the net, They seem to look the same

[WQ9E]

The GSB-101 used a center tapped plate transformer with a pair of 866A rectifiers.  The GSB-201 (at least the last two versions and I think all of them) used a solid state full wave bridge, no center tap.

[W2VW]

The Derb lived like 3 years longer because of the 201 I gave him. his goal was to use it. Unfortunately he got it working again.

[WD5JKO]

I have a 201 here, and it is like Roger says, FWB no CT. It also uses a large choke as a negative lead filter to make a choke input power supply. There are a few issues as seen in mine:

1.) The fan stops after a while, needing a re-lube.

2.) The filaments are grounded on one side, so there is 60 hz cathode modulation..maybe 10% or so...nice sine wave. To remedy this you can remove the ground, and then make an artificial center tap with something like a 6.3V CT filament transformer as a center tapped choke. I used a 50 ohm 25 watt rheostat in mine. Get that adjusted either side of center and you can see the modulation appear.

3.) There is a "Tune" position that inserts a big power resistor in series with the B+. Be prepared for it to be either broken in two, or burned up. There are better ways to do this such as a step-start turn on, and then tune initially with reduced drive.

4.) The input SWR is low 40-10m, but on 80m it is over 5:1..not sure why. I use a 'L' network when on 80m that is in a box about 6" (RG-8) away. That brings the gain up, and the positive peaks are better too with the tuned cathode on 80m. The AMP could use a tuned input on all bands.

 Mine will do 140 watts AM 80-15 all day long with headroom for 140% positive peaks, or about 200 watts with reduced modulation. On 10M the pi-net seems to get hot, and the tuning drift..It is OK though at 100 watts carrier. I have Cetron 572B's in mine.

Jim
WD5JKO