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Author Topic: AL-80B meter in AL-80A  (Read 3311 times)
AE6RF
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« on: October 12, 2008, 04:36:09 PM »

Hello all,

The meter in my AL-80A went bad. Our friends at Ameritron sent out a AL-80B meter to replace it.

Installed it and all...

Except that the scales aren't the same as the AL-80A meter.

The plate current goes from 0-1000 ma instead of 0-700.
The high voltage goes from 0 - 4000 V instead of 0-3500.
The Peak RF Watts goes from 0 - 2000 W (the same).

How should I read the new meter?

Should I trust the new scales?
Or should use the needle position, but against the old scales?

Help?

73 de Donald
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KB9CRY
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« Reply #1 on: October 13, 2008, 02:17:04 AM »

How should I read the new meter?

The same way as before.

Should I trust the new scales?

The scales are just on the meter; the meter does not affect the incoming signal to it.

Or should use the needle position, but against the old scales?

Read the meter.
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K0BG
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« Reply #2 on: October 13, 2008, 05:51:14 AM »

I don't know for a fact without checking the schematics, but I'd bet the movements are the same, but the multiplier resistors are different. You can download the schematics and look for yourself.

Alan, KØBG
www.k0bg.com
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KA5N
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« Reply #3 on: October 13, 2008, 06:38:50 AM »

Since the meter was supplied by Ameritron did they supply any additional parts or information?  If not, did you ask them if the meter was a direct replacement or required some parts changes?  
A meter usually has some full scale current rating and a resistance specified both of which are easy to measure with a DVM (if you don't know how, please check in a handbook or on the web for the simple procedure to keep from ruining the new meter).
The schematic available for the AL-80B is almost impossible to decipher and I don't have a schematic for the AL-80A so I can't give you specifics.
Allen
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W3LK
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« Reply #4 on: October 13, 2008, 06:54:13 AM »

My 80A schematic lists both meters as "1 ma, 300 ohms". It shows both meters coming of the FP-140 board with nothing between them and the board.

73,

Lon - W3LK
Naugatuck, Connecticut
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W1QJ
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« Reply #5 on: October 13, 2008, 08:02:14 AM »

If the meters have the same movement and the scales are different, then the meter will not read correctly.
Ameritron does not have meters for the AL-80A anymore, but the meters for the Al-82 or Al-1200 or Al-1500 are the same, all you have to do is change the scale.  I am doing this right now as I have an Al-80A in here for repair with 2 bad meters, so I am getting 2 meters from an Al-82 ans changing the scales.  That is the way to do it.
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W3LK
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« Reply #6 on: October 13, 2008, 10:35:23 AM »

Louis:

I have a question for you. I will be appreciative if you drop me a note at majorlk@att.net.

Thanks,
73,

Lon - W3LK
Naugatuck, Connecticut
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AE6RF
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« Reply #7 on: October 13, 2008, 03:15:16 PM »

OK,

Meter movement/ratings are the same, but the scales are different, so I will "normalize" the new scales.

For instance max Ip is 400 mA for CW. That would be 400/700 on the old scale, so it would be about 570/1000 ma on the new scale.

I'll try this into a dummy load when I get home. Pretty sure that it will lead to a follow on question...

73 and thanks,

Donald
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KA5N
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« Reply #8 on: October 13, 2008, 03:24:50 PM »

If the meters are the same, you can just take the old scale off and put it on the new meter.  At any rate if the old scale doesn't fit but the movements are the same (current full scale) then you can take the new scale off and use your computer drawing program to make a new scale just like the old one sized to fit.  
There are more ways to kill a dog than choking him to death with butter.

Allen

Notice:  No animals were harmed while writing this reply.
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W1QJ
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« Reply #9 on: October 14, 2008, 06:38:32 AM »

If the meters are the same, you can just take the old scale off and put it on the new meter. At any rate if the old scale doesn't fit but the movements are the same (current full scale) then you can take the new scale off and use your computer drawing program to make a new scale just like the old one sized to fit.


The problem is that the AL-80B meters are cross needle meters and the AL-80A are basic panel meters, no way the scales will be the same.
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KA5N
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« Reply #10 on: October 14, 2008, 09:57:02 AM »

In that case the supplied meter must have been from some other amp or the original poster would have said something like: "how come there are two scales and two needles"?
Looking at pictures of the different Ameritron amps, indicates that several amps have two meters and a meter switch while the AL-80B has two cross pointer meters.  The single movement meters all look alike and if they indeed have the same specs then a simple scale change would suffice.
I'm getting a headache.
Allen
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AE6RF
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« Reply #11 on: October 14, 2008, 10:00:11 AM »

I got whatever they send out when asked for a replacement meter for the AL-80A.

I ASS*umed* it was an AL-80B meter.

Sorry.

73 de Donald
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W1QJ
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« Reply #12 on: October 14, 2008, 12:52:35 PM »

 got whatever they send out when asked for a replacement meter for the AL-80A.

I ASS*umed* it was an AL-80B meter.

Sorry.
The AL-80B has cross needle meters unlike the AL-80A, if the meter has the same single needle but the scale is different, then they sent you an AL-82 meter which is the same meter as the AL-80A with a different scale.
This is what they are doing now if you need an Al-80A meter, they tell you to chage the scale on the Al-82 meter. Soooooo.....I think you have an Al-82 meter, so change the scale and install it and it will be fine.
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WB4JZY
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« Reply #13 on: October 17, 2008, 03:03:39 PM »

If you don't want to change the scales,  Ameritron will sell you a precision resistor kit to add to the al-80a that enables the meter to read properly with the new scale plate.
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