TOF Tuning Aid

AL811 Changes

AL811 Tuning

811A Tube History and Construction


Power line voltage jumpers in AL80B mainframe. This includes the AL572 and AL800 series.

E to F and 1,2,3 concern buck-boost, to fine adjust the voltages. The pictured setting is for 115/230 volts, without any buck or boost. These pictures ONLY concern the jumper wires. The board used for photo has no transformer connected to transformer pads.  






Supplemental Trouble Locating Hints


TROUBLE SHOOTING guide below generally applies to many types of amplifiers with suitable part number changes.

(In order of most common occurrence)


1.) Test on SSB using MOX or push-to-talk with no mic gain. With no RF drive power, but the amplifier keyed, the amplifier’s grid current meter deflects about the same as the plate current meter. This is a common problem

2.) Grid meter moves backward, and Ip meter reads forward, with no drive and amplifier in standby

3.) Amplifier blows fuses when power switch is turned on (always use proper 250V fast-blow fuses), blows step-start in other amplifiers

4.) HV/Plate Current meter reads flakey, tapping or rocking switch while in Ip position makes meter jump around (AL811 series only)

5.) Low Power Output

6.) Noise in receiver and/or erratic amplifier meter readings on standby


7.) Audible popping noise and/or clicking noise

8.) No receive or weak receive


9.) No or very little transmit power with amplifier on, OK on bypass

10.) VSWR goes intermittently high on the RF power output meter(s) when tuning

Plate or grid meters jump around with a steady carrier while VSWR changes

o     Try tuning the amplifier into a dummy load with any antenna tuner in bypass or direct

§      If the amplifier tunes up ok with the dummy load connected, you have a tuner, feed line or antenna problem

o     Change tuner output to a dummy load, and tune into the dummy load with amplifier in standby.  Now try the amplifier 

§      If the VSWR reads ok with the amplifier, you have an antenna system problem

§      Wiggle cables behind amplifier to see if connector or cable loose or bad

o     Check center pins of connectors to be sure poor soldering or bent pins have not ruined connectors

§      Too much solder on male pin will ruin female connector

§      Unsoldered male or improperly assembled male will cause poor connection

§      Some import cables and connectors are manufactured wrong size. Try different cable for better fit


11.) Transmitter or transceiver SWR too high through amplifier, should be under 1.5:1

12.) Grid meter pins with low drive power

13.) Amplifier does not appear to key, or does not release




2011 Oct 07