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Author Topic: ft-890 frequency instability  (Read 10802 times)
KK4RHF
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Posts: 35




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« on: November 12, 2013, 11:41:10 AM »

I did search and did not find anything recent on this subject so I will ask my question.
My FT-890 that I bought for $350.00 was a steal I know, but the frequency is not  stable. While talking on my first DX adventure things were working pretty good. Made contact with the Santa Maria, Azores and very little tuning was required and I was not running a linear.
Now even after being on for a half an hour the frequency suddenly will shift and I have to re-tune.
It is a sudden shift like a bad solder joint or something like that. Hearing the SSB nice and clear and all of a sudden it's off and everybody is sounding like Donald duck. Has any body encountered this before?
If so how did you fix it?
Any help will be appreciated and don't worry about getting technical I do tech speak like a first language.

73's
James
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KD0REQ
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Posts: 2054




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« Reply #1 on: November 12, 2013, 12:22:30 PM »

the usual culprit is the 10 pF trimmer on the master oscillator.  if you don't have the tcxo, that's where to start.  oxidation of the wiper contact.  you might be able to wobble the cap and reset it back where it started and get by, or you might have to replace it.  I have not dug into mine yet because of how deeply it's buried in there.  many times a good long warm-up will help but sooner or later it needs to be addressed.
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KK4RHF
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Posts: 35




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« Reply #2 on: November 12, 2013, 06:54:47 PM »

That's going to be my first check. Thanks.
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KA4POL
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Posts: 2409




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« Reply #3 on: November 13, 2013, 07:18:35 AM »

There is a step by step guide: http://fkurz.net/ham/ft890/
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KK4RHF
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Posts: 35




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« Reply #4 on: November 14, 2013, 10:05:59 AM »

This site is a life saver. Thanks for the tips!

73's
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KK4RHF
Member

Posts: 35




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« Reply #5 on: November 18, 2013, 01:31:36 PM »

There is a step by step guide: http://fkurz.net/ham/ft890/
I disassembled the radio as described and I was double checking it against the manual and without any problems got to the trimmer cap. worked it back and forth quite a few times and reassembled the radio and made some improvement in the wire dress inside. Reassembled and tested the radio and all is perfect! If it goes off frequency again I'll replace the trimmer or try to locate the optional higher stability oscillator.

Thanks to KA4POL for the expert advice! Exactly the information I needed.
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N8YQX
Member

Posts: 99




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« Reply #6 on: November 18, 2013, 03:29:29 PM »

There is a step by step guide: http://fkurz.net/ham/ft890/
I disassembled the radio as described and I was double checking it against the manual and without any problems got to the trimmer cap. worked it back and forth quite a few times and reassembled the radio and made some improvement in the wire dress inside. Reassembled and tested the radio and all is perfect! If it goes off frequency again I'll replace the trimmer or try to locate the optional higher stability oscillator.

Thanks to KA4POL for the expert advice! Exactly the information I needed.

How did you tune the trimmer cap?  Did you just mark the starting point, and return it there, or did you do more fine tuning?

My backup FT-890 has the same problem, and I was thinking about tuning the capacitor by "watching" WWV on PSK waterfall to fine tune the capacitor.
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73,
N8YQX
KK4RHF
Member

Posts: 35




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« Reply #7 on: November 18, 2013, 05:32:36 PM »

How did you tune the trimmer cap?  Did you just mark the starting point, and return it there, or did you do more fine tuning?

My backup FT-890 has the same problem, and I was thinking about tuning the capacitor by "watching" WWV on PSK waterfall to fine tune the capacitor.

I studied the screw slot position for quite a while and then I put a ceramic pot tweaker with a position marked on the rubber grip and on the  Local Oscillator shield(A piece of scotch tape works good for the shield marking) and turned it six rotations one direction and then six the other direction. I repeated that probably 10 times.
Since you have to really dig deep into the radio I felt I should work it so may I would not have to come back in and do it again too soon. Make your marks on the tweaker and the LO shield close to each other so it is easy to line up. I checked WWV and it was spot on.
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