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   Home   Help Search  
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Author Topic: 811H help  (Read 3024 times)
K8UMD
Member

Posts: 18




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« on: May 12, 2014, 06:51:49 PM »

Help, Just recently After a antenna issue I replaced my coax to my loop antenna. the original coax got water in it or something causing it to show high SWR. Until this issue this antenna loaded very well on all bands.
Now since I have replaced the coax, I can load up the amp and it works perfect on 3.747 or 3,755 or any where on 80.But when I try to work on 160 or 40 it will show around 125 watts out and then drop back to the 45 watts  input . I have checked all coax jumpers ,tried different tuner and  coax switch that is in line.
What could be causing this problem?
Could it be a bad tube? Could I damaged something when the GOP shut down the
amp,when I had a coax problem going to the antenna?
Thanks for reading my post and any Ideas you might have
Dan
K8UMD
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W1QJ
Member

Posts: 1521




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« Reply #1 on: May 12, 2014, 08:17:51 PM »

If the amp operates normal on 80 meters with normal output and smooth loading, you can't have a bad tube or else it would be problematic on 80 also.  When you changed the coax you must have lowered the antenna to work on it.  Loops could be tricky .  You may have had it up just right.  Are you using a tuner?
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NO2A
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Posts: 845




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« Reply #2 on: May 12, 2014, 08:18:18 PM »

What swr are you getting with just the rig on 160 and 40m? Sounds like an antenna problem is causing the rig to fold back power. Apparently it`s ok on 80,as you said. A dummy load would be helpful to check amp output,but if it`s ok on 80,chances are the amp is fine.
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K8UMD
Member

Posts: 18




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« Reply #3 on: May 12, 2014, 09:00:16 PM »

thanks for your response..yes I'm using a tuner and I have tried two different tuners (Palstar AT1KM and a LDG1000) just to make sure it wasn't a tuner problem.
It has the same problem into a Heathkit Cantenna.
That's why I'm suspect of the Amp.
I have a couple of 811'S handy. I guess I should try changing
Tubes out one at a time.
 Dan
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WX7G
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Posts: 6328




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« Reply #4 on: May 13, 2014, 03:07:44 AM »

What is the exciter doing on 160 and 40 meters?
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K8UMD
Member

Posts: 18




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« Reply #5 on: May 13, 2014, 05:16:01 AM »

When I run just the exciter without the amp I can get 100 watts .

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N3QE
Member

Posts: 2426




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« Reply #6 on: May 13, 2014, 05:21:26 AM »

Symptom: Amp works fine on one band, but presents high exciter SWR and low output power on other bands.

Solution: Check the alignment of the input bandswitch wafers especially whether shaft coupler has come loose.
http://www.w8ji.com/al811_input_switch_alignment.htm

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K8UMD
Member

Posts: 18




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« Reply #7 on: May 13, 2014, 09:15:16 AM »

Thanks for your information Tim.
I will take a look at the band switch wafers as soon as I get a chance to pull the cover off.
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K8UMD
Member

Posts: 18




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« Reply #8 on: May 13, 2014, 05:55:08 PM »

I checked the band switch wafers. everything appears to look good.
I clean the contacts again. I put the top back on and as I was loading up
the amp on the dummy load and the wife was at her desk next to mine .
she said she heard what sounded like a chattering or arching.
I didn't have my hearing aids in...it's hell getting old
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WX7G
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Posts: 6328




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« Reply #9 on: May 13, 2014, 06:57:57 PM »

What does the exciter do when driving the amp on 160 and 40 meters?
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K8UMD
Member

Posts: 18




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« Reply #10 on: May 14, 2014, 05:41:48 AM »

the exciter runs about 65 watts while I try to tune up amp
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K8UMD
Member

Posts: 18




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« Reply #11 on: May 14, 2014, 04:40:28 PM »

Today I pulled the cover off amp looking for the noise the wife heard.
I tuned it up on 40 meters..Held the safety switch and keyed the mic and saw arching
on the plate capacitor. I immediately shut it down.
what would cause this? It doesn't look dirty.
And a few weeks ago I blew out the amp with a compressor.
could I have caused this by using a compressor?
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K8UMD
Member

Posts: 18




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« Reply #12 on: May 15, 2014, 07:31:31 PM »

 Thanks everyone for your help. The problem has been solved.
The arching that I was hearing was coming from the plate capacitor.
while the antenna was down I took the amp out to the garage to blow
it out with the compressor. I learned a lesson..not a good idea.
I moved one of the capacitor plates a little to close to the other.
After a very delicate operation I'm back-up and running on 40 and 160 with
full power out and no arching.
Again thanks for all your comments and help.
I learn something new everyday..I just hope I can remember it.

Dan
K8UMD
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