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Author Topic: Kenwood TH-79A display problems  (Read 7687 times)
N0NNE
Member

Posts: 5




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« on: May 22, 2002, 12:05:38 AM »

Display started to fade out a few months ago, Now it is displaying all kinds of symbols and junk. Sometime it even starts to scroll.tried a master reset and it helped for 30min. Any ideas?
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S56KZN
Member

Posts: 10




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« Reply #1 on: June 16, 2002, 09:25:01 AM »

Did not try it myself, find this display problem fix somewhere on the net.


There are often contact problems between the main board and
      the display. To fix the problem fasten the screws at the
      backside of the display. Now the display should work again.
      You can lock the screws with some nail-paint for example.
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W8BLB
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Posts: 1




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« Reply #2 on: June 21, 2002, 04:07:24 PM »

I had this same problem on my TH-79. The repair was fairly simple. Once you remove the three screws from the back of the unit and seperate the two halves you will notice there is a fairly long ribbon cable going between the two halves (this is the display connector.)

I simply reseated the ribbon cable and tightened the PCB screws and this fixed the problem.
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KC5LNU
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Posts: 1




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« Reply #3 on: May 30, 2007, 09:42:44 AM »

My twelve year old TH-79A all of a sudden got the garbled display bug.  After researching the matter, here's how I fixed it:

Phase 1:  Remove the four case screws, three on the back, one on the side (under the rubber cover).  Open the case and notice the silver ribbon connecting the board to the display.  There is a connector that connects the ribbon to the board.  The connector has a brown "rail" or bar on one side.  Gently lift the rail, one end at a time.  The rail stays up by itself, you don't have to hold it up.  Once lifted, the ribbon is released from the connector. Pull the ribbon out of the connector and then reinsert the ribbon and push the rail back down.  I did this procedure to both ends of the ribbon.

Phase 2:  I don't know why this needs to be done, but it's easy so I did it.  Just loosen the board's mounting screws and retighten.  Actually, I did this to all the mounting screws I could get to.

I reassembled and powered it up.  The display was back to normal.  There was no memory loss with these procedures.

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PE1RLN
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Posts: 24


WWW

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« Reply #4 on: October 14, 2012, 12:06:44 AM »

It has been a while since the previous post but the display problems still occur these days.

I posted my solution on mods.dk but the problem with strange and scrolling characters was new for me. However, all the above solutions may work. I simply disassembled the entire unit and built it back together. After that, all contact were loosened and maybe cleaned by removing them. Any way, it worked.

So display problems on your nearly antique (mine is 16 years old now, still going strong!) TH-79 can be solved by these methods.
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WB2GFC
Member

Posts: 3




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« Reply #5 on: August 24, 2014, 09:50:41 AM »

Display garbling problems are usually due to one of two items:

1) The flat cable between the 2 parts of the unit
2) The "zebra strip" just underneath the bottom of the LCD display

For #1, sometimes just reseating this flat cable (also known as an FFC) will work. Other times, this 26 pin cable will have problems internally, and you'll need to get a new one. This is a 26 pin FFC 0.5mm pitch (I assume this is the correct pitch, don't quote me on this), and usually comes in a 2000mm (20cm or 8 inch?) length, and I am told some DVD players use this. Truthfully, I would use the part 880H04-7377-82 from an online parts retailer, just because its said to work with the TH-79A.

For #2, this Zebra Strip, aka part e29-1123-05 or 881H96-8890-02 is a conductive rubber strip just underneath the LCD display of the unit. To get to this, you actually have to de-solder the two posts outside the bottom left and bottom right of the display, and CAREFULLY remove the display. It says to clean the conductive rubber with rubbing alcohol, but for me I'd rather replace it, then clean where it comes in contact with the PCB. Remember to re-solder the display back onto the two posts, using proper soldering techniques, and check for cold solder joints.

I've also CAREFULLY and LIGHTLY cleaned the keypad surfaces.

Disclaimer:
This post is not all inclusive, nor do I take responsibility for you ruining your TH-79A by using poor soldering, incorrect parts, or poor disassembly practices. You are responsible for your own equipment, and should review ALL documentation concerning this fix, not just this post. Disassembly procedures are in the "TH-79A Service Manual" available at several places on the web. The lock button is especially tricky to remove, so take extra special care not to break it. Also, recommended you do this in a clean area where you can easily locate parts if they drop. Take notice and follow all precautions. You are responsible for your own repair and your own equipment.
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W8JX
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Posts: 5665




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« Reply #6 on: August 24, 2014, 04:37:04 PM »

Display started to fade out a few months ago, Now it is displaying all kinds of symbols and junk. Sometime it even starts to scroll.tried a master reset and it helped for 30min. Any ideas?

You can try some of the suggested fixes but that display is also known to fade and fail with age and there are no spares to be found.
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