Dentron GLA-1000 C Amplifier


Welcome to this third description page regarding the sonic page Dentron GLA-1000C Model HF RF-Amplifier. If you've located this page while looking for Dentron GLA-1000 "plain" or "B" information, be sure to return to the main sonic web page for the remaining two downloads regarding those models. It would actually be a good idea to have all three of the sonic page Dentron downloads for review.

The GLA-1000C Amplifier was the last of the GLA-1000 amplifier series sold before Dentron went out of business or possibly became Amp Supply, followed by Amp Supply's demise. There is a direct similarity between the Amp Supply LA-1000 amplifier series and the Dentron GLA-1000 lineup. Don't forget to have a look at the Amp Supply download information. The last and fairly rare GLA-1000C traded the 10-Meter band position for 160-Meter operation in Compliance with revised FCC rules.

The revised bias circuit for the GLA-1000C

The dentronc.zip file download is the full sized circuit diagram for the Dentron GLA-1000C model amplifier. Of particular note is the revised cathode bias circuit and receive mode (idle) current cut-off resistor. The bias circuit consisting of the PNP Transistor and 21 volt 1 watt zener is worth a look. The transistor essentially expands the zener diode's power handling capacity, eliminating the original costly high power GLA-1000B/C circuit stud-mounted zener. Improvement to this circuit might include additional RF-bypassing through the use of additional capacitors. Current technology replaces this circuit with an updated constant-voltage bias regulator using the stable and predictable TL-431 Adjustable Precision Shunt Regulator.

My Original Dentron Upgrade Article focus's on the lack of cathode current cutoff in the earlier GLA-1000 amplifiers. The Article available in one of the other www.radiowrench.com/sonic web page Dentron GLA-1000 file downloads has been "lifted" by many an amplifier person.

One of my few complaints with persons lifting the information regards their incorrectly reposting the cathode current cut-off mode picture. Somehow most of these people modify the 75K cathode cut-off resistor location from my original text. Please notice the resistor always remains in series, the relay contact merely shorting (bypassing) the resistor out of the circuit in transmit mode. Most of the erroneous circuit redraws show the resistor "switched in line" via a relay pole connection. There is a very short portion of relay switching time where neither the Zener Diode, nor the 75k cut-off resistor, remains in series with the cathode return circuit. I consider this briefly un-terminated tube cathode lead connection very bad news and a source of potential trouble. A comparison of my cathode cut-off circuit Vs other redraws should clearly show my point. The relay, resistor, zener and bypass disc capacitors should be connected as shown in my original text. Also note the GLA-1000C bias circuit above shows the proper cut-off resistor connection.

One should also review my original Dentron Article meter and glitch protection information. The mentioned glitch protection improvements help to prevent needless costly repairs. I'm always happy to answer your Emails should you have a question or two.

Many and special thanks to Wm D. (KC0RSG) for sending the full size diagram (a reduced size preview is shown just above) and some of the pictures you see of his actual working Dentron GLA-1000C HF RF-Amplifier.

enjoy
skipp


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