AL80B AL572 AL800 AL800H Correction Kit
Note: I also have AL80 and AL80A/SB1000 parts.
This $25 shipped kit corrects the easier field-correctable flaws put in the AL80B over time. These corrections include:
(For units with small enclosed relays, rather than large open frame relays)
1.) Restoring relay operating time from the current 20-30mS closure time to time<8mS
2.) Correcting relay sequencing errors
3.) Correcting relay line impedance sensitivity, which cause premature loss of receive
(for later production year units after a transformer vendor change)
4.) Correcting grossly excessive 12Vdc line voltages, which damage the metering op-amp. This was caused by a transformer ordering error
(for all units of all years)
5.) Improvements to the auto-bias circuit
6.) GDTs to improve radio and amplifier protection in the event of a tube arc
I strongly suggest owners of the AL80B, AL800, AL800H, and AL572 read this link:
About the AL80 History
I was responsible for the AL80 series starting in 1983 until MFJ took over. The first AL80 was a Twinsburg design Prime Instruments inherited. Ameritron-Prime recalled all known AL80s and remanufactured them to Ameritron-Prime standards. Remanufactured units were assigned S/N 300 and up. Revised new units were S/N 500 and up.
The larger and higher-performance AL-80A was the first full Prime design, replacing the AL-80 in the mid-1980s. I sold the kit rights, with some modifications, to Heathkit as an SB1000.
The AL80A ran until replaced by the AL-80B. The AL80B frame and main circuit board, with a different transformer, were also used in the AL-572, AL-800, and AL-800H.
The AL80B had a larger transformer and more features than earlier AL80 amplifiers, including true peak-reading directional coupler wattmeters and a very special design ALC circuit. The AL80B and other amplifiers in this mainframe, including the AL572, AL800, and AL800H all have grid current derived ALC. The Ameritron solid state amplifiers and the AL80B style mainframes are the only amplifiers I almost insist on being used.
Unfortunately, once designs were turned over to MFJ pretty much anyone, whether they understood circuit function or not, would randomly change things. Instead of improving reliability and performance over the years, which is the normal direction designs should go, amplifiers deteriorated.