AL-811H Problem or Not?

[WA7PRC]

Lou makes a good point about duty cycle. Except, when I drive my SB-220 "up the wall" at 100% D/C for a long period, the breakers don't blow. It could be...

• The breakers are sized so they won't trip during normal use or
• The breakers are defective and should've tripped or
• I'm not pulling near enough AC current to trip them

With fuse and circuit breaker sizing, I prefer to err on the side of safety. If it blows/trips, only THEN would I consider stepping up to a larger value.

[WB2WIK]

The D/C stuff is certainly true and valid for almost everything involving "heating."

I don't trust fuses to save tubes, I trust them to prevent fires. Usually if a tube is involved in popping a fuse or breaker, at that point it's too late to save it.

[W4HWD]

That's a big 10-4...my first amp was an AL-811 back 20 years ago. I had the same problem. It was wired for 120V but had 8A fuses in it. That thing, on carrier tune up will pull close to 15A...the correct fuses fixed that problem and it ran fine for years until I had a 220 line installed and went to an AL-1200.

[WA7PRC]

It's exceedingly easy to measure the AC line current instead of blindly selecting fuses. That assumes the manufacturer is clueless. If they aren't, it's even easier to determine proper fusing.

[WB2WIK]

That's a big 10-4...my first amp was an AL-811 back 20 years ago. I had the same problem. It was wired for 120V but had 8A fuses in it. That thing, on carrier tune up will pull close to 15A...the correct fuses fixed that problem and it ran fine for years until I had a 220 line installed and went to an AL-1200.

Seems to me the AL-811 ought to draw about 10A key-down full power; but the 811H ought to draw more like 12-13A, making 12A fuses a really poor choice.

I did contact Ameritron about what appears to be an error in their manual, and they agreed "Ooops" and to fix that in future publications of the manual.

I honestly don't know if they have any technical writing staff of any kind, at all. Possibly not.

Then, I found errors in the Collins 30S-1 manual; and dozens of errors in Henry amplifier manuals; and Dentron manuals almost never agreed with the actual construction; and on and on it goes!

Someone brought me a Commander amp to repair last year, and the "as discovered" circuits in the totally unmodified amplifier disagreed with the manual (schematic) in at least a dozen places.

At least hams can modify and fix stuff, unlike commercial users.

[WA7PRC]

I did contact Ameritron about what appears to be an error in their manual, and they agreed "Ooops" and to fix that in future publications of the manual.

What actual measured current did they observe and/or what size (and type) fuse did they say should be used?

[W4HWD]

Seems to me the AL-811 ought to draw about 10A key-down full power; but the 811H ought to draw more like 12-13A, making 12A fuses a really poor choice.

I did contact Ameritron about what appears to be an error in their manual, and they agreed "Ooops" and to fix that in future publications of the manual.

I honestly don't know if they have any technical writing staff of any kind, at all. Possibly not.

Then, I found errors in the Collins 30S-1 manual; and dozens of errors in Henry amplifier manuals; and Dentron manuals almost never agreed with the actual construction; and on and on it goes!

Someone brought me a Commander amp to repair last year, and the "as discovered" circuits in the totally unmodified amplifier disagreed with the manual (schematic) in at least a dozen places.

At least hams can modify and fix stuff, unlike commercial users.

Back when I got the 811 I used a "clamp around the cord" current meter of dubious accuracy to get the current reading. I have always been leary of running any HF amplifier on 120VAC, which is why later on I paid the electrician to install a 220 line in the shack I had at the time. Then, of course, I felt the need to use it (!) so I sold the 811 and got the AL-1200...

Oh and also the first thing I did back then when I got the 811, on the advice of some guys on 75M, I dumped the 811 tubes and replaced them all with 572B's...the 572B's had thicker plates. I'm not too proud to admit that, in the past, I have ruined a couple 811 tubes by getting them so hot the plates collapsed! Never had that problem with 572B's...live and learn...

[AG6K]

Lou makes a good point about duty cycle. Except, when I drive my SB-220 "up the wall" at 100% D/C for a long period, the breakers don't blow. It could be...

• The breakers are sized so they won't trip during normal use or
• The breakers are defective and should've tripped or
• I'm not pulling near enough AC current to trip them

With fuse and circuit breaker sizing, I prefer to err on the side of safety. If it blows/trips, only THEN would I consider stepping up to a larger value.

 If the circuit breaker trips during extended key-down I would not increase the amps rating.
. I would measure the R of the parasitic suppressor resistors to make sure that an intermittent parasite was not involved. I would also add a suitable surge-rated resistor -- a.k.a. "glitch-R" -- in series with the HV+ to avoid grid-fil shorts and add 3A Si diodes across the meter movements.

[W1QJ]

 if the circuit breaker trips during extended key-down i would not increase the amps rating.
. I would measure the r of the parasitic suppressor resistors to make sure that an intermittent parasite was not involved. I would also add a suitable surge-rated resistor -- a.k.a. "glitch-r" -- in series with the hv+ to avoid grid-fil shorts and add 3a si diodes across the meter movements.

'this has been a recorded announcement"