The Dentron GLA (Great Little Amp)1000b is a compact 1200w input HF amplifier which is often found quite reasonably priced on the second hand market because the valves it uses are not really up to the job in this application. The 6LQ6's are also now starting to get hard to find = expensive, £35 is the cheapest I've seen them, £60 the dearest! and you need 4! As I like construction I decided to convert the amplifier to take the widely available = cheap, ($25 + p+p typical) Gi7b ceramic triode. 6LQ6 = 35W anode dissipation, Gi7b = 350W, it doesn't take much to work out which will be more reliable! If you intend to try this yourself, Ted Lee's (N8NPQ) website is invaluable.
This is what the amplifier looks like with the lid off. WARNING - This unit contains lethal voltages and should only be opened if you understand the risk, people have been killed by valve amplifiers! In the modification the power supply is converted to a doubler supply giving about 2200v which will not give you a second chance if you touch it! I cannot be held responsible if you decide to overload your mortal coil!
This is a shot of the modified amplifier, with new cooling chamber, toroidal filament transformer and new larger tank coil. If you want to ask any questions about this project or any other on the site please email me.
The converted amplifier is now giving good service and reliably producing more power on all bands than it did although I don't know how fresh the original valves that I had were. Note the re-scaled meter with a "wait" LED which lights during the valve warm up time, the operate relay is disabled during this time too.
Ted Lee's GLA1000 modification site
amplifier info page
This page has been removed from its original location as geocities is no more, it is however still available at the "web.archive" site. This link takes you to the archived page although it isn't 100% reliable.