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Author Topic: Ameritron 811 issue  (Read 2722 times)
F5VDM
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Posts: 11




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« on: November 20, 2011, 08:50:11 AM »

HI

I have an Ameritron 811A which is working okay on 40m, 20m and 15m.  When I tune it to 10m however, I notice that even in SSB mode, when I key up, there is a carrier which is at the 300w output level, i.e. a carrier without voice input. Also I cannot tune the amp to more than this power level.  The tubes are new btw.

I am under the impression that the amp is not working on this band as although I have tried to make 10m contacts, no-one seems to hear me.

It does work on 12 metres btw, although I can only get a max of about 300 watts out.

any ideas?

thanks

Garry



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F5VDM
Member

Posts: 11




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« Reply #1 on: November 20, 2011, 12:21:38 PM »

Seems to make sense, I'll check it out tomorrow.  Thanks

Garry
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K1ZJH
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Posts: 1009




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« Reply #2 on: November 20, 2011, 12:39:28 PM »

Quote

HI

  When I tune it to 10m however, I notice that even in SSB mode, when I key up, there is a carrier which is at the 300w output level, i.e. a carrier without voice input. Also I cannot tune the amp to more than this power level.  The tubes are new btw.

I any ideas?

thanks

Garry


Stop using the amp on ten meters immediately!!!!  If you are seeing 300 watts outut on ten meters SSB with no mike audio, either the
exciter or the amplifiier is oscillating on its own! Something is very unstable, and you will damage the radio or amp.
Hopefully W8JI will join in, I'm sure he has some suggestions.

Pete
 
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W9KDX
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Posts: 770




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« Reply #3 on: November 22, 2011, 03:21:10 PM »

Might not be the issue, but mine had the 10 meter slug turned in waaay too far to the point that I had massive SWR issues until I backed it out about 3 turns.

Mine still has issues on 40 meters with the plate current running too high with any kind of watts out from the transceiver.  I am assuming you mean the 811H.
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Sam
W9KDX
NG4F
Member

Posts: 4




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« Reply #4 on: November 22, 2011, 06:37:44 PM »

Quote

HI

  When I tune it to 10m however, I notice that even in SSB mode, when I key up, there is a carrier which is at the 300w output level, i.e. a carrier without voice input. Also I cannot tune the amp to more than this power level.  The tubes are new btw.

I any ideas?

thanks

Garry


Stop using the amp on ten meters immediately!!!!  If you are seeing 300 watts outut on ten meters SSB with no mike audio, either the
exciter or the amplifiier is oscillating on its own! Something is very unstable, and you will damage the radio or amp.
Hopefully W8JI will join in, I'm sure he has some suggestions.

Pete
 
you are correct. mine was doing the same thing. it blew a tube,and blew the finals out of the radio.
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K0ZN
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Posts: 1548




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« Reply #5 on: November 22, 2011, 08:04:11 PM »

It does sound kind of suspicious, but the first thing you need to do is absolutely and positively confirm your tranceiver that is driving the amp is working
correctly on 10 M and that you have it set up correctly (not on RTTY or something generating a carrier). Without seeing your station set up it is pretty hard to diagnose by long distance, etc. Make sure all your interconnection cables and connectors are good (tight connections, good soldering/crimping,etc to insure cable integrity).

Which amplifier do you have?? Ameritron makes two amps using the 811A tube; the three tube AL-811 and the four tube AL-811H. The two have a slightly different
circuit.

Make sure your antenna load is proper and correct on 10 M (low SWR, etc.)  You really need a dummy load to start checking out the amp.

I have an AL-811 (3 tube) and so far, it appears totally stable on 10 M although tuning of the Plate and Load knobs is VERY critical. Be sure to start at LOW power to look for the proper tuning. i.e. adjust the Plate and Load controls for maximum output. There is not much room for mistuning on 10 M.  BE SURE to observe the cautions
in the owner's manual about not holding the amp in transmit for more than a few seconds and allow an equal cooling off period. This is important; you CAN quickly
ruin the tubes if you hold it in transmit for very long in an "out of tune" condition.)

If you feel the need/desire to open the amp up, the first thing I would do is CAREFULLY check is ALL of the grounding connections/screws solder joints. Unfortunately, it is typically a very good idea to go through an Ameritron amp and check EVERY screw and nut....EVERY....screw and nut to be sure it is tight. They have had some
quality control issues in this area from time to time. I did find a "dangerously" loose screw/nut on a critical grounding lug on my AL-811. Fortunately, I caught it before initial operation.

Go to W8JI.com and read EVERYTHING he says about the proper way to tune an amplifier.  Well worth your time.

A more detailed description of your station set up and antenna, etc. would be helpful.

73,  K0ZN
« Last Edit: November 22, 2011, 08:09:08 PM by K0ZN » Logged
W8JI
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Posts: 9296


WWW

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« Reply #6 on: November 23, 2011, 01:11:39 AM »

HI

I have an Ameritron 811A which is working okay on 40m, 20m and 15m.  When I tune it to 10m however, I notice that even in SSB mode, when I key up, there is a carrier which is at the 300w output level, i.e. a carrier without voice input. Also I cannot tune the amp to more than this power level.  The tubes are new btw.

What amp do you have Garry? Is it the AL811, or the AL811H?

How old is it?

Did this problem start when anything else changed?

Quote
I am under the impression that the amp is not working on this band as although I have tried to make 10m contacts,
no-one seems to hear me.

When something appears to not be working, it is best to not use it.


What is the entire setup? Where do you have the tuning and loading set?
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F5VDM
Member

Posts: 11




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« Reply #7 on: November 23, 2011, 05:33:02 AM »

Thanks for the replies.

What amp do you have Garry? Is it the AL811, or the AL811H?  How old is it?

AL811H

Its an oldish one, I bought it 'second user' from the US

Did this problem start when anything else changed?

Yes, I changed my 10m antenna, but it IS a resonant, 5/8 wave vertical

When something appears to not be working, it is best to not use it.

I am NOT using it on 10m, but it works fine on the other bands

What is the entire setup? Where do you have the tuning and loading set?

FT 920 - 1/4 wave vert for 40m works fine.  Multiband dipole for 20 - 10 inc WARC, works fine and low swr on all bands.

5/8 vertical low swr, works fine.

Amp fine on all bands, except 12/ 10m.  I notice that there is a lower carrier on 12m but it tunes and work on 12m, its on 10 that it is not working at all.

Radio is fine, no issues.  Not using ALC.  However - Plate Load settings on all bands seem to be way off the settings in the manual.

The amp puts out fine power on 80/40/20/17/15, 12 is very very touchy, but seems to work (only abt 300 watts though) and 10 not at all..


thanks

Garry

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K1ZJH
Member

Posts: 1009




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« Reply #8 on: November 23, 2011, 06:20:16 AM »

HI

 .  When I tune it to 10m however, I notice that even in SSB mode, when I key up, there is a carrier which is at the 300w output level, i.e. a carrier without voice input. Also I cannot tune the amp to more than this power level.  The tubes are new btw.

 any ideas?

thanks

Garry


Hi

I'm seeing some conflicting statements in later posts. Does the amplifier show 300 watts RF output on SSB when you
are not talking into the mike on 10 and 17 meters? 

Pete
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F5VDM
Member

Posts: 11




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« Reply #9 on: November 23, 2011, 06:25:04 AM »

Apologies.

Let me recap.

Amp works ok on all bands except 12 (power lower than expected - but works) and 10 (carrier at 300 watts when in SSB - doesnt seem to work)

thanks

Garry
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W8JX
Member

Posts: 5904




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« Reply #10 on: November 23, 2011, 09:14:11 AM »

Apologies.

Let me recap.

Amp works ok on all bands except 12 (power lower than expected - but works) and 10 (carrier at 300 watts when in SSB - doesnt seem to work)

thanks

Garry

I suspect there is some instability in amp and it is oscillating on 10. Also with 811'a and 572's there will be some power drop off at higher frequencies too. (depending on how healthy tubes are) 
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W8JI
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Posts: 9296


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« Reply #11 on: November 23, 2011, 09:27:27 AM »

What amp do you have Garry? Is it the AL811, or the AL811H?  How old is it?

AL811H

Its an oldish one, I bought it 'second user' from the US


The AL811H, if everything is proper inside, is unconditionally stable. This is because it is neutralized.

This does not mean it always will be stable if it has a problem, like a broken wire, open ground connection, or some other defect.

There is a stability test you could do, and it doesn't need to as complicated as shown on my web page.

Basically, do NOT connect your radio. Connect the antenna normally to the output, a dummy load to the input, manually key the amp by grounding the center pin of the RLY jack, and rotate the plate tune and loading controls and see if you can get the meters to move around. If it does, and if the HF power meter shows significant power, the amp is unstable. The 811H should NEVER show power in this test!

A more involved test is here, but it may give you some idea what you are looking for.

http://www.w8ji.com/testing_for_stability.htm

Hard telling what shape things are in with an older used amp.

Quote
Did this problem start when anything else changed?

Yes, I changed my 10m antenna, but it IS a resonant, 5/8 wave vertical

It should be immune to antenna changes. Something else is the real root cause. Something changed inside the amplifier in a major way.   

Quote
[Radio is fine, no issues.  Not using ALC.  However - Plate Load settings on all bands seem to be way off the settings in the manual.

The amp puts out fine power on 80/40/20/17/15, 12 is very very touchy, but seems to work (only abt 300 watts though) and 10 not at all..[/b]

What are the Plate and Load settings on 10 meters?

Do not use it on 10 or 12 for now.

73 Tom
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