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Author Topic: simple al-80a question  (Read 1649 times)
KJ4MYY
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Posts: 34




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« on: August 11, 2010, 07:54:50 PM »

I was given an al-80a with a broken multifunction switch.  Since I don't know what it was supposed to be like, maybe someone can answer this before I cut it on.  There are 4 positions on the face of the amplifier it can be turned to, but the switch is a 6 position switch.  I need to know where I need to set the know allen screw so the knob lines up with the correct function.  Where are the 2 dead positions?  Both to the left of HV?  Both to the right of ALC, or one to the left and one to the right?  Thanks for your help on a hopefully simple question.
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AD6KA
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Posts: 2243




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« Reply #1 on: August 12, 2010, 12:00:41 AM »

I was given an al-80a with a broken multifunction switch.  Since I don't know what it was supposed to be like, maybe someone can answer this before I cut it on.  There are 4 positions on the face of the amplifier it can be turned to, but the switch is a 6 position switch.  I need to know where I need to set the know allen screw so the knob lines up with the correct function.  Where are the 2 dead positions?  Both to the left of HV?  Both to the right of ALC, or one to the left and one to the right?  Thanks for your help on a hopefully simple question.
Some previous owner blew the original switch
and replaced it with a six postion switch.
The 4 postions on the METER switch are
CLOCKWISE: HV, Ip, PO, ALC.
Quote
Where are the two dead positions?
Where you place the switch and have no meter functions at all,
assuming there aren't any goofy modifications.

OK, turn on the amp, switch to Standby, NO power in.
Unless you have a dummy load and anyway you wont need it here.

Do not attempt to operate this amp until you know
the meter switch is turning on the indicated meter.

Take off the knob and get a pair of pliers.
Turn the switch ALL THE WAY TO THE LEFT. If nothing happens
(no meter movement) it's a no connection.
Make one turn to Clockwise.
No meter deflection, move clockwise again.
Get a meter deflection?
That's the HV (plate voltage) reading. About 2,700 volts no load.
Put the knob back on with the pointer to the HV indicator.
Tighten securely.
Moving clockwise, each turn of the switch should
be the next indicated "function" The next "functions" will be
Ip Plate Current  Should be zero at idle.
PO (watts out) should be zero at idle
ALC, should read zero at idle.

So...the first furthest counter clockwise switch position
that gives you a meter deflection (the ONLY meter you'll have deflection at idle)
will be HV, the plate voltage.

Hope this helps.
73, Ken AD6KA
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KJ4MYY
Member

Posts: 34




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« Reply #2 on: August 12, 2010, 03:48:42 AM »

Thanks for the answer, I will check it out once I get a 120VAC power plug on it to plug it in. I have already changed the 240/120 jumpers.  The interesting thing on the switch is I got it form Ameritron.  I called then and asked for a replacement and that is what they sent me.  So I just assumed that that must have been what originally was on it as well. Oh well. I couldn't tell how the original one acted as it just spun in a circle with no clicks when I got it. 
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W1QJ
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Posts: 2908




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« Reply #3 on: August 12, 2010, 04:30:48 AM »

The replacement switch is indeed a 6 position and so is the old one,but only 4 are used,  If you look carefully the old switch will have a metal round disc with a tiny tab.  Be careful not to discard that disc from the old switch.  You will also see a small "tit" if you will on the switch.  There is also a relief in the chassis for the "tit" to line up the switch in the chassis so it doesn't rotate around when you turn the knob.  You will want to take the switch in your hand and orient it with the "tit" on the chassis so you know which way you will be installing it.  When you do this turn the switch all the way to the left stop.  Then advance the switch 3 clicks.  After you do that, you have to insert the metal disc with the tab.  This is the stop to make it a 4 position switch.  Be sure to insert the stop into the correct hole in the switch.  After you insert the stop disc, turn the switch back to the left stop and then check to see you have 3 clicks to the right and then stops.  If you get 2 or4 or 5 clicks then you set the disc in the wrong hole.  You want 3 clicks to the right after the left stop only.  There is no need to do any trial and error while the amp is running.  Then of course, be sure you wire the switch correctly.  I hope I made this easy to understand.  The metal stop disc usually falls out of place on the old switch so look carefully for it.  When you install the switch be sure that stop disc does not come out of alignment.  I have changed many of these switches.  I found that you have to drop the front panel, remove the switch and you should be able to work on it through the cut out.  The wires should just be long enough to work at the edge of the chassis.  So remember the line up "tit" and the stop disc.  Just to calrify.  When the switch is all the way to the left, that is one position, first click is position2, second click is postion 3 and third click is position 4.  4 positions 3 clicks then stop.  Be sure it is right.  The stop disc is what controls the advancement of the switch clicks (positions).  Lou
« Last Edit: August 12, 2010, 04:58:21 AM by Lou Parascondola » Logged
KJ4MYY
Member

Posts: 34




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« Reply #4 on: August 13, 2010, 07:16:59 PM »

Thanks for the help.  Worked out great.
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K4RVN
Member

Posts: 260




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« Reply #5 on: August 13, 2010, 08:37:23 PM »

The circuit board and switch replacement I got from Ameritron was a six position. A simple way to align the pointer is to tighten the set screw then turn it until you get around 3100 volts on the meter with the amp in standby. Then align the line on the knob on HV and re tighten the set screw. That will be in the correct position. Turning to all positions whether used or not does not hurt anything on my AL 80 A. Glad you already have your problem corrected. You will enjoy that amp after you get familiar with it.

Frank
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