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Author Topic: al 811h plate current meter  (Read 480 times)
N4ZY
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Posts: 81




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« on: January 31, 2010, 01:47:17 PM »

i have a al 811h plate current meter that is not lightin up. meter works fine. bulb is not blown.(checked with ohm meter) grid meter fine. any directions??
                     thanks jim N4ZY
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WB2WIK
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Posts: 20666




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« Reply #1 on: January 31, 2010, 03:14:56 PM »

Ameritron switched from bulbs to LEDs recently.  Don't know which yours has.

But just because the bulb shows some continuity doesn't mean everything is good to go.

Did you check the VOLTAGE across the bulb?
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N4CR
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Posts: 1700




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« Reply #2 on: January 31, 2010, 03:19:59 PM »

i have a al 811h plate current meter that is not lightin up. meter works fine. bulb is not blown.(checked with ohm meter) grid meter fine. any directions??
                     thanks jim N4ZY

There is a schematic here:

http://www.ameritron.com/man/pdf/AL-811H.pdf

Looks like there is a winding from the transformer that drives a full wave bridge and a couple of caps. That is the voltage source for the bulbs and it's directly connected to the bulbs with no switching or other control. Check the output of that bridge rectifier for DC output and go from there.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
WB2WIK
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Posts: 20666




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« Reply #3 on: January 31, 2010, 05:18:22 PM »

An Ohmmeter continuity measurement is meaningless if the bulbs in the two meters are wired in parallel, which they are.

Your meter could have a completely "open" filament, and if you measure across it with an Ohmmeter, it won't show open, it will show resistance because the other bulb is still good.

You can't rely on this for any information, at all.

You need to remove the bulb from the circuit (entirely) and then measure it independently.
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KA2UUP
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Posts: 388




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« Reply #4 on: February 01, 2010, 06:36:05 AM »

Suggest checking with Tom, W8JI.  He designed the AL-811H and is a frequent contributor to this forum.

Good luck DE KA2UUP, Bert
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KD8GEH
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Posts: 482




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« Reply #5 on: February 01, 2010, 09:36:11 AM »

If the other bulb works, that only leaves the wire to the bulb and the bulb. My moneys on the bulb.  I've replaced quite a few.  Even cheap rad shacks will do in a pinch. Ameritrons are a little pricy, check mouser or digi-key.

73, Dave  KD8GEH
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