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Author Topic: FT-897D Tuning  (Read 826 times)
W7XK
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Posts: 3




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« on: May 09, 2009, 07:43:19 AM »

The main tuning/VFO dial on my FT-897 seems to tune in reverse.  Rotating clockwise the frequency decreases.  I cannot seem to find a menu item to change the direction.  My FT-950 tunes conventionally.  Is this just a idiosyncracy of the 897 or can I change this somehow?
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N3OX
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« Reply #1 on: May 09, 2009, 08:09:48 AM »

"Is this just a idiosyncracy of the 897 or can I change this somehow? "

I think it's neither.

Did you buy a used, repaired, or refurbished one?

It sounds like the encoder is wired backwards.  An optical shaft encoder will work just fine if you swap the two quadrature outputs, but it will work in reverse.

I wonder if it ever had the encoder replaced and the replacement was the wrong sense of rotation?  I think there can be a very subtle difference in part numbers for otherwise identical units from a given manufacturer with the rotation phase reversed.

I have a FT-857D which, as far as I know, is really the same radio in a different box, and I can't find anything in the regular menu or service menu that would affect the dial rotation.  I thought maybe the "transverter" settings could affect this but it doesn't seem like there's an inversion option.

If you exhaust all possibilities in firmware, I think it must be the hardware, and I would think it would probably be a pretty easy fix if you just figured out what your shaft encoder was, figured out which the "A" and "B" outputs were, and swapped them.  If the encoder is not soldered directly to a circuit board but is attached with wires, it could be an easy fix apart from disassembly/reassembly.   If it's soldered down to the board, you'd have to do some trace cutting surgery...

 73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
K6RQR
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Posts: 203




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« Reply #2 on: May 09, 2009, 05:12:09 PM »

Hello -
 That is an unusual problem you have. Was the rig bought used? If so, I'm assuming that someone did some work on the encoder. However, it is odd that they didn't mention this to you before purchase. If the rig was purchased new then it will probably be necessary for you to return it to Yaesu for warranty repair.
 I own an 897D and it does not tune this way ordinarily.
Good luck getting it fixed and I hope you enjoy the rig. It is quite versatile and fun to use.

73,
Bruce  K6RQR/9

 
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W7XK
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« Reply #3 on: May 09, 2009, 06:19:49 PM »

I did indeed buy the rig used.  It works flawlessly except for this one glitch.  I have an email out to the fella to ask.  I looked under the hood and there does not appear to be an obvious transposition of wiring.  May have to go to Yaesu for repair.  
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N3OX
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« Reply #4 on: May 09, 2009, 07:53:06 PM »

"there does not appear to be an obvious transposition of wiring"

There doesn't have to be.  Looks from the service manual that the encoder has a wiring harness ... it would be possible that the "wrong" part would just plug and play... backwards.

I don't know if sending to Yaesu for repair would be the most cost effective if all that needs to be done is that the encoder pins need to be flipped... because encoders are often kind of expensive and I'd guess the "modification" to just re-do the wiring is not something Yaesu would probably be willing to do.

But you never know, might be worth looking into.

As far as I can tell, the RES20d50-201-1g is what you have, based on the service manual: http://www.nidec-copal-electronics.co.kr/upload/rec_res_en.pdf

They do NOT seem to offer two reversed parts, so I don't know what's up with that.

Any decent tech with a scope should be able to do the mod quite quickly even if it's not obvious what the encoder's "A" and "B" outputs are.  Of course, whoever fixed the thing shouldn't have got the encoder swapped anyway.

If it were my rig, I would have just finished cutting , swapping, soldering, and heat-shrinking the green and white wires :-)  (Seriously, are they red, black, green and white and come directly out of the encoder?  That would be my guess from the service manual's suggestion of part numbers)

You can actually probably check it with a multimeter.   One wire (red, if it's the  encoder from Copal) should be +5V, one (black) should be ground.  The other two should either be 0 or 5, and since they'll change FAST when you rotate the knob, you could check them on the AC meter setting.  They should read 0 VAC when you're not spinning the knob and I suppose something in the ballpark of 2.5VAC when you spin the  knob...   all this should be plugged into J4004 on the panel unit board.  There are some test points there, TP4008 and TP4010 should be the "A" and "B"  

Anyway, I don't want to give you over-confidence that I'm exactly right about the problem or the solution.  I'm making this up as I go along.  I just want you to have this in mind  when you are looking for repair folks.  I don't want you to have to pay for a new encoder if you've got a working one that just needs its leads swapped.

The only tricky/dangerous/risky part of playing around with it is static electricity.  The encoder goes straight into an important CPU.

I also don't know exactly what would happen if one of the A or B outputs on the encoder failed in this radio.  I would think tuning would be strange and erratic or not work at all, not just smoothly backwards, but who knows...

73
Dan




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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W7XK
Member

Posts: 3




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« Reply #5 on: May 09, 2009, 10:23:17 PM »

Yep, there are 4 wires coming from the main VFO knob and they are red, green, black, and white.  The plug into the board is designed similar to a very miniature rigrunner.  I swapped the green and white but no joy.  Still runs backward but a bit more erratic now.  Will swap back and hope for the best.  Thanks for all your help.  I was really excited there for a bit.  

73,

 John
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N3OX
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« Reply #6 on: May 10, 2009, 07:20:04 AM »

OK... well, I think there might be something more wrong with the radio.... like the encoder isn't properly encoding or the CPU isn't properly decoding.

Maybe a silly hack would work for a while?  How about installing a second tuning knob on a heavy base underneath the radio that just rubs up against the edge of the first?

:-)

Sorry to hear it wasn't simple.  

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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