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Author Topic: FT-1000D Low TX Output - SWR Sensing Circuit issue  (Read 4270 times)
W4QG
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Posts: 26




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« on: January 19, 2012, 05:30:53 AM »

Hello All,

I am having an issue with a recently acquired FT-1000D. It APPEARS that the SWR circuit is folding back the transmitter output. Into a known good dummy load I am only getting about 25w out of it. I notice that the rigs SWR meter spikes when the rig is first keyed, in some cases it settles back, in others it does not. Interestingly, on some bands the AT locks fairly quickly, on others, it does not find a match (I realize I may be looking at two different issues). Looking through the schematics and from what I have read on line I believe the first place to look would be the SWR diodes D7201-D7204. Before I crack open this radio, any FT-1000 experts out there have any other suggestions? I have found a few scattered posts on the net related to this issue, apparently it is not an unknown problem. 

On a side note, I have been looking for the FT-1000 mailing list, it appears to be down. Anyone know anything about that?

Thanks and 73,
Paul W4QG
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WA0ZZG
Member

Posts: 158




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« Reply #1 on: January 19, 2012, 05:49:51 AM »

Paul;

I need to know more.
How are you running this test?
Dave
WA0ZZG
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W4QG
Member

Posts: 26




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« Reply #2 on: January 19, 2012, 07:23:46 AM »

Hi Dave,

Pretty simple at this point. Connect coax cable to main SO-239. Cable goes to Bird 43 and from there to dummy load. (cables, load etc known good) Hookup key. Power up rig. Set rig for 7.1MHz, CW, with RF Output turned fully clockwise. Key the radio. With the meter set in SWR position I see a momentary spike to infinity SWR then it settles down to approximately 2.5:1 or so (sorry, at work right now, don't have rig in front of me, but you get the idea). Carrier out of the radio is at about 25W. As I recall, other parameters measured by the meter are what one would expect with that output power level. Behavior basically the same whether the tuner is engaged or not

Thanks for taking the time to answer my post.

73,
Paul W4QG
 
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KE3WD
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Posts: 5689




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« Reply #3 on: January 19, 2012, 08:18:35 AM »

Suspect something amiss in the output filtering bank.  Likely a stuck relay or shorted relay driver, something like that which would be keeping one or more of the filters inline when it should not be. 

Sometimes you can chart out the performance by band and get an idea of which filter is on when it should not be.  Bear in mind that these are lopass filters.  So, if, for example, you obtain full power on 80 and 40, but it starts to fall off on 20 and above, suspect that the 40 meter filter is on when it should not be, etc. 


73
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W4QG
Member

Posts: 26




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« Reply #4 on: January 19, 2012, 10:38:02 AM »

That thought occured to me as well, but the output seems to be pretty flat on all bands. However, I will go through and check all bands just to be sure. Thanks!
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KB2CPW
Member

Posts: 304




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« Reply #5 on: March 04, 2012, 11:07:10 AM »

There were always problems in the swr and foldback circuits in those. Check the diodes in the foldback, if they are bad, the radio will not produce full output. Usually the tuner will not work right and hunt around for a match.
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WA0ZZG
Member

Posts: 158




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« Reply #6 on: March 05, 2012, 11:05:26 AM »

Yes, the FT-1000D transmitter is very modular with the PA in one module, the Low pass filter elsewhere and the VSWR sense seperated.  It's well built, but has many little connectors in the RF path along with relays and PIN diodes. Also, if you're testing in CW, make sure the drive control is turned up.  This is actually a bias control that gets sent to several locations depending on mode.  It is possible to seperate the modules and test them that way. Also make sure the cooling system is OK.
Dave...
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BX6AP
Member

Posts: 1




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« Reply #7 on: July 20, 2012, 01:51:11 AM »

Dear OM:
               Please check ft-1000 service manual about  "CM coupler Balance"  in page 4-6 . Use multimeter  check pin3 of J7023 IN LPF board  ,voltage out. Key tx in 14.1mhz and   tune TC7201 to minimum volt , maybe 0.5V~02V


If it is up tp 2~5V , It will be D7201-D7204 NG. Please replace D7201-D7204 . After replace and check pin3 of J7023 and  tune TC7201 to minimum volt .

You will see output up to 200W....


Please check these pics. http://www.facebook.com/media/set/?set=a.412709848765343.82850.100000789939230&type=3&l=63bcd5401a

good luck , BX6AP / KJ6CGP
« Last Edit: July 20, 2012, 01:59:59 AM by BX6AP » Logged
W7APM
Member

Posts: 25




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« Reply #8 on: July 24, 2012, 01:20:41 PM »

I had the same problem with one of mine. Turned out to be in the filter board
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