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Author Topic: ICOM 756 Pro 3 ALC meter not working and low power out  (Read 2713 times)
NS3Q
Member

Posts: 12




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« on: June 28, 2012, 02:22:36 PM »

Greetings to the Elmer's.

Icom 756 pro 3 ALC meter not working (zero) and max power 30 watts all modes, but the SWR, power, and compression readings all function properly. All external equipment and cables except mic (Tokyo HP amp, Rigblaster Pro) has been disconnected and SSB output is still only 30 watts with 1:1 SWR (measured with external meter before and after).

IALC voltage should be 0 to -4 vdc range. Have Service Manual and have removed the top and bottom covers of the rig for inspection. Also have the schematic that came with rig.

One last clue - 80 meters output is 100 watts ?? Other bands it's 30 watts max out.

I'm ready to start taking measurements on the test points and would appreciate any info on where to start with my volt meter. NO scope here to test with so voltage and continuity checks are it.

Tnx for taking time to read post and hoping for help.

73,
Clint NS3Q
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KE3WD
Member

Posts: 5689




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« Reply #1 on: June 28, 2012, 06:40:21 PM »

What does the rig by itself do when connected to nothing but a proper Dummy Load? 
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K7MH
Member

Posts: 339




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« Reply #2 on: June 28, 2012, 10:49:43 PM »

One possibility is that the rig just needs to be reset.
I would first try it on a dummy load as mentioned and see how it goes.
Start with the simple things first.
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NS3Q
Member

Posts: 12




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« Reply #3 on: June 29, 2012, 08:09:21 AM »

Tnx for the replies.

I do not use a dummy load, I tune my antenna with MFJ SWR analyzer to a flat 1:1 before operating each time. Then I switch in the rig thru my Alpha Delta coax switch.

The back up rig is operating fine all modes - all bands 160m-10m. The problem IS IN the 756 pro 3 as mentioned before.

Guess it's time to troubleshoot using the service manual and volt meter. I was hoping someone had experience testing inside this model rig and would share some info.

The problem has to be in the 756 pro because I can switch in the backup rig without changing any settings and it is fine. Both rigs and MFJ analyzer attached to Alpha Delta switch 4 way switch, maybe I should troubleshoot switch setting #4 (756 pro attached here). Backup rig on switch posistion #3 and MFJ SWR analyzer on posistion #1.

73, Clint NS3Q
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NS3Q
Member

Posts: 12




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« Reply #4 on: June 29, 2012, 11:14:36 AM »

K7MH
I'm interested in your keep it simple and reset the radio.
Would you pse explain the reset process?

I have removed the CMOS battery to clear all my settings, and there are many reset points in the service manual.
These are mostly EEPROM from what I can tell and some are on the main CPU.

Used backup rig to check things on Alpha Delta switch posistion #2 of 4, which was previously unused and all was good.

Think I'll try the 756 pro again on the prev unused switch posistion #2 and maybe I'll get lucky.

Hoping to hear about your reset process and tnx for post!!

73, Clint NS3Q
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NS3Q
Member

Posts: 12




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« Reply #5 on: June 29, 2012, 02:51:54 PM »

Tnx for all the help guys.

Sending it to Icom in WA so they can do it right. Will be for sale after repairs and in the mean time I'm off to buy a new one!

That 7700 looks like something I could use!

Tnx agn, Clint NS3Q
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K6AER
Member

Posts: 3524




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« Reply #6 on: June 29, 2012, 03:46:58 PM »

Make sure the antenna tuner is off.
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KB1YNB
Member

Posts: 1




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« Reply #7 on: September 05, 2012, 09:43:56 PM »

Greetings to the Elmer's.

Icom 756 pro 3 ALC meter not working (zero) and max power 30 watts all modes, but the SWR, power, and compression readings all function properly. All external equipment and cables except mic (Tokyo HP amp, Rigblaster Pro) has been disconnected and SSB output is still only 30 watts with 1:1 SWR (measured with external meter before and after).

IALC voltage should be 0 to -4 vdc range. Have Service Manual and have removed the top and bottom covers of the rig for inspection. Also have the schematic that came with rig.

One last clue - 80 meters output is 100 watts ?? Other bands it's 30 watts max out.

I'm ready to start taking measurements on the test points and would appreciate any info on where to start with my volt meter. NO scope here to test with so voltage and continuity checks are it.

Tnx for taking time to read post and hoping for help.

73,
Clint NS3Q






Hi, I'm looking to buy a Icom  756 pro3, to all who read this. I am KB1YNB a Med retired DAV home bound. Danbury, Ct CARA member. I need to purchase a Icom 756 pro 3 because it has all the Hallmarks of what I desire in a home base. My Max is $1500 and am asking any one who can help me find one I would so very much appreciate there help. I just got my license to keep my mind mentally active being home bound I've been going nutz, and so having looked at many units I fell in love with this one and is a bit out of my price range and so need help finding one that is.k you Gentleman to please help me please. 73 KB1YNB.
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