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Author Topic: TS-850 Display  (Read 3030 times)
N8NSN
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« on: July 25, 2008, 02:05:50 PM »

Before I remove the screws (as I have had to many times for other problems) I want to get a hand full of ideas on what to look for in my Kenwood TS-850S/AT.

The problem is that everything in the radio is working,TX,RX etc.  I can enter a frequency with the keypad and set modes as well.  The problem is that the display is completely dead.  It went out with no warning of dimming or blinking or any indications that a failure was coming.  Any ideas on what to look for?  I have read 1 probable cause on the K 0 B X TS-850 page that the  Cap on the inverter that supplies the display might be bad.  I just want to get a few more suggestions before I pull it out of service and remove the screws once again.  Yep, The 850 is OLD but worth the effort to keep it on the air.  

Thanks,
jimmie KC8BYF
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N3TUZ
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« Reply #1 on: July 25, 2008, 04:23:33 PM »

Suggest you do a RESET of the rig before removing all those screws and delving inside.  Worked for me with an FT-757GX that exhibited the same symptoms you describe, and it just might work for you.  By the way, I found nothing in the book on how to do a reset and came across the procedure on the internet, quite by accident, but only after the radio had been gathering dust on the shelf for several years.  This radio is still in use today, with a much better receive audio than the FT-890 I bought to replace it.
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K0OD
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« Reply #2 on: July 25, 2008, 04:48:30 PM »

Can you post a link to the reset info?  I didn't know that was possible.

Yep, my old '850 is a great radio. I almost wish it would die so I'd get an excuse to buy a newer generation toy with IF DSP, 6 meters and a separate receive antenna port.  But I doubt a new expensive toy would be a better radio for most purposes.
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WB2WIK
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« Reply #3 on: July 25, 2008, 06:10:31 PM »

I doubt the master reset will restore the display.  More likely the inverter that powers the display is malfunctioning, and that's "fairly" common, although it never happened to my TS-850S, which I've owned since it was new in 1990.

However I've always noted the display is slow to "ignite" if the rig is operated in a cold temperature environment.  Even when it was new, if I took it outside to operate in 40 degree (F) weather, the display would come on maybe a minute or so after the rig.  So, that inverter circuit is temperature influenced and evidently marginal, right from the start.

WB2WIK/6
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N8NSN
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« Reply #4 on: July 25, 2008, 07:41:58 PM »

I reset the 850 per pressing A=B while turning unit on.  That resets the microprocessor for the whole rig.  I need to know if there is a "hard reset" procedure that isn't mentioned in the owners manual.

Also, I found the Information about C18 that is in the inverter circuit section of the display unit.  That is the cap that seems to have a high failure rate.  

I have the service manual on the TS 850 but there is nothing in the trouble shooting process to suggest any failure or repairs of the display.  However, the owners manual, in the trouble shooting section, mentions the "A=B power on" reset procedure for a blinking display (unlocked PLL) or if the display is blank.  Did that to no avail.  Again, Is there a hard reset procedure not mentioned in the manual?

Thanks KC8BYF jimmie
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AH6RR
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« Reply #5 on: July 25, 2008, 07:59:28 PM »

C18 is the problem. Replace it and check any damage it might have caused when it leaked and repair that also. If you have your 850 interfaced to your computer any rig control program like Ham Radio Delux should show where the radio is. If you do not feel that you are up to repairing the radio yourself then I would suggest AVVID Radio @ www.avvid.com Clif is a great Kenwood Tech. I hope my 850 last many years to come because it is one of the best radios ever made.

Good Luck & 73
Roland AH6RR
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N8NSN
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« Reply #6 on: July 27, 2008, 06:52:50 PM »

To Everyone:


I want to thank everyone for their input at this time.  You guys (several) were right on the mark and I really appreciate it.  It was indeed C18 on the display board.  At first glance I thought this was going to be a real hassle to do the work in a timely manner.  One individual informed me that I would have to unplug all the flat ribbon cable and modular connections to the face in order to get to the display unit.  After looking a little closer at the rig I found this to be completely false.  Four screws on the sides of the face assy. and an easy flip over and turning the face 180 degrees and laying it on top (actually bottom) of the rig... 5 screws that hold the display unit and only 1 ribbon cable to unplug.  "Piece of cake" as some would say. The only hold up was that I was out of 470 ohm 16V electrolytic caps.  So, tomorrow (Monday) I am off to the parts surplus store to replenish my stock of common caps.

BIG NEWS... After removing C18 I started "ringing out" traces associated with this cap and it's pre and post components, as C18 left a mess of goo on the PCB.  Sure enough the trace coming from #2 of the transformer to the + side of C18 had been eaten through.  The "crack" was so fine that without the "ringing out" process I would have never seen the fracture (even under the jewelers mag lamp).  The two feed through lands for C18 were in fair shape but, needed a slight amount of dressing up.  After a small amount of time in fixing the one trace with a small jumper all points are ringing out fine now with the meter.  So, tomorrow morning after I get the cap soldered in and the check is performed I am hopeful that the "dead display dilemma" is concluded in good standing.

  By the way... Kenwood service manuals are not very good (in my opinion).  The C18 is never mentioned in the circuit schematic and the traces on the PCB views in the service manual are IMPOSSIBLE to distinguish.

With fingers crossed I am hopeful that this is all that was wrong with the display.  If this isn't the end of the story I will absolutely re-post with further questions.  

Thanks again to all & 73,

jimmie KC8BYF Dayton, Ohio
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N4NYY
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« Reply #7 on: August 24, 2008, 08:19:15 AM »

I repaired one with the dead display. The caps on the display board leak and eat away the traces. The problem is that you cannot tell, unless you remove the caps. It is not visible with the caps in place. I think there were 3 caps with common values (I used higher voltage caps like 35V or so). I purchased them at Radio shack for $4. I also used some wire-wrap wire, which I soldered to components to replace the eaten away traces. Worked like a charm and my friend couldn't believe I just fixed his radio for $4.

I hope you didn't spend alot of money in parts order because this is a common failture with these. Good luck !
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WK4U
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« Reply #8 on: January 04, 2009, 09:39:35 AM »

I can add to this thread.  Based on info here, and two other Internet sources, I had a bad capacitor (C18) on my display board.  It also hurt a trace from one side of the capacitor that I had to jumper with a small wire.  As others have said, you can't SEE the damage, so get out your trusty ohm meter and check.

My display started going off, then on and off again at random.  Everything else worked fine.  Since replacing the capacitor, the display works correctly again.  Radio Shack had the exact capacitor in stock.  Slightly larger since it was 32 VDC, but still worked fine.

When you take the front panel off the radio chassis, have the radio turned upside down first, then flip the front panel over onto the bottom side of the radio.  From there, you remove 5 or 6 screws and a single ribbon cable to remove the display board.  Total repair time probably just over an hour.

Good luck!

-Tim
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W8BNL
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« Reply #9 on: March 30, 2009, 03:40:09 PM »

My display has never gone blank (see pic at http://tommywhitewolf.hostse.com/TS-850SAT-Panel-W8BNL.jpg) Instead - everything is lit. Moving the VFO or any other function makes all the characters in the display jump and change. I use Ham Radio Deluxe at the moment to keep the radio on the air since it still receives and transmits fine. Any suggestions for this one?Huh Many thanks in advance - W8BNL Tom
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N1EQ
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« Reply #10 on: March 31, 2009, 03:48:35 AM »

W8BNL:

The lithium battery probably has leaked, corroding traces on the digital board. And IC2 (CXD1095Q) might have been affected, since it is below the battery. IC2 controls the display.
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