Have you very closely inspected the input band switch contacts? Maybe spray them with deoxit and move them around some? The contacts always fail
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
-
A Winner has been selected for the 2025 Radioddity Cyber Monday giveaway! Click Here to see who won!
AL-811H problem/ question
- Thread starter Crambone
- Start date
Something is blocking the tracks. This is where a 'scope is your friend.
Pulling the plug makes it safe to poke inside. A handy bench-type 12-Volt DC supply is used to energize only the amplifier's relay circuits. A current limit if 1 Amp or other protection is a good idea.
Putting the amplifier on "operate" and keying the radio will now feed drive into the tube's cathodes. They won't care since the filaments are cold.
Turn down the radio's CW output to 5 Watts or so. Should make life safer for the radio. Key the radio and probe the output of the relay's input side. Comparing the RF voltage you get to what's on the center pin of the radio's coax socket will reveal loss of driver power.
The tuned-input circuit will show (I think) a slightly-higher signal level at its output than at the input. Finally, seeing the drive level on each side of the blocking capacitor that feeds the tubes' cathodes. Is the last link in this chain.
Something is blocking the tracks. Since your DC continuity tests eliminate the relay as the culprit. Tells us this is a fault in some AC component that can't be tested with a DC meter.
We know the tracks are being blocked somewhere between the relay and the tubes' cathodes. Question is where?
73
Pulling the plug makes it safe to poke inside. A handy bench-type 12-Volt DC supply is used to energize only the amplifier's relay circuits. A current limit if 1 Amp or other protection is a good idea.
Putting the amplifier on "operate" and keying the radio will now feed drive into the tube's cathodes. They won't care since the filaments are cold.
Turn down the radio's CW output to 5 Watts or so. Should make life safer for the radio. Key the radio and probe the output of the relay's input side. Comparing the RF voltage you get to what's on the center pin of the radio's coax socket will reveal loss of driver power.
The tuned-input circuit will show (I think) a slightly-higher signal level at its output than at the input. Finally, seeing the drive level on each side of the blocking capacitor that feeds the tubes' cathodes. Is the last link in this chain.
Something is blocking the tracks. Since your DC continuity tests eliminate the relay as the culprit. Tells us this is a fault in some AC component that can't be tested with a DC meter.
We know the tracks are being blocked somewhere between the relay and the tubes' cathodes. Question is where?
73