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Posted: 4/30/2016 1:12:06 PM EDT
I'm sure some remember the thread recently about my 706 with no power out. Well, I sent it to Scott at MTS in Washington and explained the problem to him. About two weeks later when he is able to work on it, he emails me back and tells me that he can't find a problem with it on any band or mode that he tries. He keeps it another week, tests it multiple times, no problems at all, so he sends it back.
Well I get it back yesterday evening and put it back in the truck this morning, lo and behold I have no output on any HF band in any mode. I bring it in the house and hook it up using the cable for my 718 to see if maybe it's an issue with the cable in the truck to no avail, still nothing. Emailed the repair guy back and he said "looks like the the driver or final is dead, can't explain why it worked while it was here". Does anyone have any other ideas, I'm at a loss? |
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Have you tried all modes?
AM/FM/CW/SSB? Tried VHF and HF? Using external or internal watt meter? |
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Have you tried all modes? AM/FM/CW/SSB? Tried VHF and HF? Using external or internal watt meter? View Quote Tried all modes on HF, internal and external meter plus amp meter on power supply with nothing. 2m and 440 seem to work fine, had a long conversation on a local repeater a few minutes ago. |
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Does it indicate that it is trying to transmit on HF when you press the mic PTT button? Get any sort of indication that the PTT circuit is working?
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Does it indicate that it is trying to transmit on HF when you press the mic PTT button? Get any sort of indication that the PTT circuit is working? View Quote View All Quotes View All Quotes Quoted:
Does it indicate that it is trying to transmit on HF when you press the mic PTT button? Get any sort of indication that the PTT circuit is working? Yes it does, light turns red, I can hear it click over Quoted:
Shake it Is there by chance a screw rattling around inside? Nope, nothing rattling |
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does your power meter indicate on the Ic-718 ?
did you try CW with a key ? ( mic problem ?) |
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Yes, it does. I used the 718 for ten contacts after I unhooked the 706. Tried my key as well, nothing View Quote View All Quotes View All Quotes Quoted:
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does your power meter indicate on the Ic-718 ? did you try CW with a key ? ( mic problem ?) Yes, it does. I used the 718 for ten contacts after I unhooked the 706. Tried my key as well, nothing That's a shame. Protect your final output transistors with SWR at 1.5 or better. I've read that on the IC-706, finals are not made anymore, unless you have a IC-706mkiig with a serial number higher than 15000 There are websites, and youtube videos that can show you how to modify ( dremel) your board to fit newer finals best of luck, the 706 is a great little rig. |
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Connectors are often the problem. It's always a good idea to wiggle/remove/re-seat any connector that you can get to.
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Ok, I will try opening it up and wiggle connectors. Scott just emailed back, said that it could be the mic.
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Ok, I will try opening it up and wiggle connectors. Scott just emailed back, said that it could be the mic. View Quote That wouldn't make a difference using CW or AM (since you said it is going into TX mode) and I would also rule it out based on the fact that you've used it successfully on VHF. |
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That wouldn't make a difference using CW or AM (since you said it is going into TX mode) and I would also rule it out based on the fact that you've used it successfully on VHF. View Quote View All Quotes View All Quotes Quoted:
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Ok, I will try opening it up and wiggle connectors. Scott just emailed back, said that it could be the mic. That wouldn't make a difference using CW or AM (since you said it is going into TX mode) and I would also rule it out based on the fact that you've used it successfully on VHF. Ya, true |
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That's why I asked if you tried it with the CW key Also, with USB/LSB you need to modulate, talk or whistle to swing the power meter View Quote View All Quotes View All Quotes Quoted:
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...... Scott just emailed back, said that it could be the mic. That's why I asked if you tried it with the CW key Also, with USB/LSB you need to modulate, talk or whistle to swing the power meter Was talking/whistling into dummy load, did nothing |
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EB5AGV's Workbench: Icom IC-706 MkIIG final amplifier repair A new life for old-type power amps http://jvgavila.com/ic706.htm |
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Ok, small update. I do have the mkiig with the newer finals, so they are more available but still becoming a little less common.
I tried the radio today with a different mic, different control head, different power cable, different power supply, and different stages of disassembly (parts of the case removed, etc) with the same results, so unfortunately it looks like its going to be something internal took a dump |
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Get a can of 'Freezit" spray and try to see if you can get it to come back. Spritz a bit here and there (on the PC boards) and see if it will work briefly.
Freeze It I used to use this stuff troubleshooting bad solder joints and bad/intermittent IC's "back in the day". |
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Get a can of 'Freezit" spray and try to see if you can get it to come back. Spritz a bit here and there (on the PC boards) and see if it will work briefly. Freeze It I used to use this stuff troubleshooting bad solder joints and bad/intermittent IC's "back in the day". View Quote While you are in there, check all of the TMP connectors (these are the little coax jumpers that go from board to board) and all other connectors for fit, cracks, lifted traces, etc. Given the fact that it didn't work, went for a ride, worked, went for another ride and stopped working, it seems likely to me that something is loose. My parents used to own a PC sales/service business; we'd occasionally see similar issues where the customer would bring in a machine with an issue and we would be unable to duplicate the problem, give them their PC back and the problem never appeared again. One of those things where a cold joint/ broken connector/little bit of corrosion was corrected by some jostling and there was no way that' you'd ever find out exactly what it was without hours of extensive investigation. We also used freeze spray. "Theoretically" as an alternative, you can also use a can canned air turned upside down (actually, don't do that as it's probably against federal law or something) as it's the same stuff as the freeze spray, but you know you'd never do that. |
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Thanks, guys. I will see if I can find some and give it a shot. I actually talked to a guy local to me yesterday that offered to help me troubleshoot it using his scope and such, so thinking I may take him up on it this week.
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While you are in there, check all of the TMP connectors (these are the little coax jumpers that go from board to board) and all other connectors for fit, cracks, lifted traces, etc. Given the fact that it didn't work, went for a ride, worked, went for another ride and stopped working, it seems likely to me that something is loose. My parents used to own a PC sales/service business; we'd occasionally see similar issues where the customer would bring in a machine with an issue and we would be unable to duplicate the problem, give them their PC back and the problem never appeared again. One of those things where a cold joint/ broken connector/little bit of corrosion was corrected by some jostling and there was no way that' you'd ever find out exactly what it was without hours of extensive investigation. We also used freeze spray. "Theoretically" as an alternative, you can also use a can canned air turned upside down (actually, don't do that as it's probably against federal law or something) as it's the same stuff as the freeze spray, but you know you'd never do that. View Quote View All Quotes View All Quotes Quoted:
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Get a can of 'Freezit" spray and try to see if you can get it to come back. Spritz a bit here and there (on the PC boards) and see if it will work briefly. Freeze It I used to use this stuff troubleshooting bad solder joints and bad/intermittent IC's "back in the day". While you are in there, check all of the TMP connectors (these are the little coax jumpers that go from board to board) and all other connectors for fit, cracks, lifted traces, etc. Given the fact that it didn't work, went for a ride, worked, went for another ride and stopped working, it seems likely to me that something is loose. My parents used to own a PC sales/service business; we'd occasionally see similar issues where the customer would bring in a machine with an issue and we would be unable to duplicate the problem, give them their PC back and the problem never appeared again. One of those things where a cold joint/ broken connector/little bit of corrosion was corrected by some jostling and there was no way that' you'd ever find out exactly what it was without hours of extensive investigation. We also used freeze spray. "Theoretically" as an alternative, you can also use a can canned air turned upside down (actually, don't do that as it's probably against federal law or something) as it's the same stuff as the freeze spray, but you know you'd never do that. Wow, never knew canned air is the same thing. I'll have to go get some now. Another possibility is loose board ground screws. I've fixed quite a few radios by simply backing out all the boards ground screws a bit then snugging them up. My 2m mobile is an old Kenwood TR-7730 my buddy bought at a hamfest. Didn't work when he got it home. He gave it to me. I had it on the air within the hour using nothing but a Phillips head screwdriver. |
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Does it use separate PA's for HF and VHF?
There should be a switch or relay which directs the TX thru the HF vs VHF amp. It may simply be stuck in VHF. Reason? Scott's power supply may be a slightly higher voltage than yours and the relay/switch needs that extra voltage to operate. |
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Does it use separate PA's for HF and VHF? There should be a switch or relay which directs the TX thru the HF vs VHF amp. It may simply be stuck in VHF. Reason? Scott's power supply may be a slightly higher voltage than yours and the relay/switch needs that extra voltage to operate. View Quote This is the way Scott explained the path to me: After the mic amp, one path is for SSB/AM the other path is FM. All done in the IF. The IF is common to all bands, it doesn't go through different paths until the HPF, then goes through common amplifiers, until the PA unit, whee at the driver it is split between HF and VHF/UHF. I'm still learning internals, so I'm trying to read and learn what each section does in regards to this issue |
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Troubleshoot from the output back to the input. O'scope is tailor made for this. Look at the final output first. Nothing? Go to the input of the final. Nothing? Back to the driver output, then input and so on.
Should be fairly easy with a scope and schematic. |
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Ok, I just read through both threads on your 706.
So, it quit transmitting for you in March, you sent it to Scott who had no problem using it, and you get it back and again no output. It really looks like you have a local problem, but not internal to the radio. Start with the power connector. Don't just say "it's a good one". Check everything about it: Are all the pins wired correctly and power is available where it is supposed to be? From the looks of it on the internet, there are two pins for ground and two for +12. The second +12 is usually for the PA only. How about the tuner? Do you use one? Did Scott? Which mic did he use? Do this for everything external. Bottom line is, if it worked for him, it will work for you. ETA: No I am not a tech, but worked with some of the best in manufacturing. They beat this into my head: check the power first. If the power supply train ain't good, it ain't gonna work. |
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This sounds like a fuse holder or plug crimp could be going bad ie. broken crimp, corrosion, cracked solder. Check those out, even fuses can go bad. 73, Rob |
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Ok, I just read through both threads on your 706. So, it quit transmitting for you in March, you sent it to Scott who had no problem using it, and you get it back and again no output. It really looks like you have a local problem, but not internal to the radio. Start with the power connector. Don't just say "it's a good one". Check everything about it: Are all the pins wired correctly and power is available where it is supposed to be? From the looks of it on the internet, there are two pins for ground and two for +12. The second +12 is usually for the PA only. How about the tuner? Do you use one? Did Scott? Which mic did he use? Do this for everything external. Bottom line is, if it worked for him, it will work for you. ETA: No I am not a tech, but worked with some of the best in manufacturing. They beat this into my head: check the power first. If the power supply train ain't good, it ain't gonna work. View Quote I have tried all the external stuff, four different power supplies, three different power cables, two different mics, and two different control heads. None of that has helped Didn't use a tuner, just connected to dummy load and resonant antennas, neither of those mad any different. Also tried a different antenna at a friend's house with the same results. We both went through every menu item to make sure there wasn't a setting that was changed/missed but none of that helped. I fully believe that this is something simple that can be fixed easily, I just don't have the experience or equipment to go probing around inside looking for a bad component. I'm going to download the schematics today and see if i can hook up with the local guy that offered to help me out with his bench and equipment to see if we can figure it out. Thank you everyone for all of your input, it has been a huge help trying to work through this frustration. |
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I can sympathize with you.
I like the challenge of fixing one that others have given up on, but sometimes I have to admit defeat. One of the worst I fixed in the past few years was a mobile 2m/440 that had no output but I could hear on another radio in the same room. Turns out the little metal piece inside the antenna connector had broken off and come out. Since the radio, like most nowadays has a good fold back circuit, it was not damaged. Easy fix once I found the problem. |
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I can sympathize with you. I like the challenge of fixing one that others have given up on, but sometimes I have to admit defeat. One of the worst I fixed in the past few years was a mobile 2m/440 that had no output but I could hear on another radio in the same room. Turns out the little metal piece inside the antenna connector had broken off and come out. Since the radio, like most nowadays has a good fold back circuit, it was not damaged. Easy fix once I found the problem. View Quote I'd give anything to be that easy |
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