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Strange issues with output power
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George
Hi All.
I have had an Icom IC-7000 for over a year now, having bought it second hand. Today I went to use the for a few SSB QSOs on 20 metres when I realised I couldn't get more than 40 watts out. Initially I thought that the PA amp may be at fault, but after playing around some more, I learned that the power I get varies wildly with band. Setting the radio to 100% power out, I get the following measured powers with a Bird Thruline into a dummy load: - 160 metres, 1 watt. - 80 metres, 1 watt. - 40 meters, 10 watts. - 20 metres, 40 watts. - 12 metres, 60 watts. - 10 metres, 90 watts. - 6 metres, 30 watts. - 2 metres, 49 watts (fine). - 70 cms, 37 watts (fine). It seems the issues are in the HF PA, i.e. anything on Antenna 1. I'm not sure what the issue is. I think something like a capacitor gone down, or a relay stuck? I'm not sure. Any help would be greatly received. Thanks in advance. George Smart, M1GEO. |
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dajetzi
Hello everyone, 14 days ago i ran in the same problem.
Took my radio to a A licensed friend of mine for doing some QSO in JT65 in 20m. RF power set at 30 watt, modulation level adjusted, swr was fine. After a while we noticed very low power on the display. We did a factory reset but no change. First thought PA stage get burned, then we made some test. We measured the following results. 1,9 MHz 0,8 Watt 3,55 MHz 1 Watt 7,05 MHz 5 Watt 10,12 MHz 28 Watt 14,1 MHz 30 Watt 15 MHz 35 Watt 18,1 MHz 30 Watt 21,2 MHz 35 Watt 24,95 MHz 40 Watt 28,5 MHz 60 Watt 50,1 MHz 25 Watt 2m/70cm are not affected. First it seems the filterboard does something stupid, but then we noticed the ALC display did not show correct, except on 10m. Very strange behavior. I did not try to repair the radio because it is still in warranty. So radio is sent back to the seller for repair. Today i got a call from him and apparently the driver stage got toasted. Now i have to wait until second week in January. I'm curious what comes out in your research. 73 de DO1KLM Sigi |
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George
Thanks very much everyone for your replies. I've got to wait until after Christmas before I can get time to work on it, but I will have a good look. I have access to all the gear, test sets, spectrum analyzer, scope, sig gens, etc. I need to study the diagrams a bit before, so it all makes sense, but I like the idea of checking the RX sensitivity.
As soon as boxing day is over, I'll have a look and report back. I may also curious as to 4 metres on the radio, bringing the PA out to SMA with hardline and having an external filter if the PA does any power on 70 MHz. I'll report back once I've done some work. Cheers for all the advice, it's much appreciated. 73 all, and seasons greetings. George Smart, M1GEO. |
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George
Hello again chaps :)
I've done some further investigation and I'm a little stumped as to what the next step should be. I firstly checked all of the LPF filter relays with a multimeter with the radio powered off, and confirmed that they were all in the normally-closed position, as would be expected with no power to the rig. I then measured the receive sensitivity and it seems fine, i.e. the standard (50uV = S9 for HF). I checked on all the bands, and it is the same sensitivity for them all (2m/70cm excluded, of course). If anyone has any ideas, it would be greatly appreciated. Best 73, and seasons greetings. de George, M1GEO (with help from G8OCV). |
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George
Hi.
After Christmas and my Birthday, I have been busy at work. As the radio sees a lot of use, I decided to send the radio back to Icom. The estimate they sent me was for a new RD70HHF1 FET PA. I really doubt that the device has gone, but, now I've sent it to them, I'll have to pay anyway. The transistors were marked, so I will see if they were actually replaced when the radio is returned. But ultimately as long as it works, I don't care. The total repair bill as follows: 1560001601 FET RD70HHF1-101 (?41.15) Carriage Charge (?6.50) Labour Charge (55.00) Ex VAT: (?102.65) VAT: (?20.53) Total: (?123.18) I will report back if the transistors were actually changed. Cheers, M1GEO. |
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dajetzi
Yesterday got a call from my radio repair center,
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they replace the finals and a few arounding components and now the TRX is on air again. Waiting for delivery the nexts days and hope the radio works as well as before. 73 de DO1KLM, Sigi --- In ic7000@..., "dajetzi" wrote:
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