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AB9LZ
03-15-2008, 05:59 PM
My 850's display went dark mid QSO, had no effect on the rest of the radio, the nice chat with a DK6, (tnx Werner) was completed successfully.

As I hunt for the schematic, does anyone have any hints?, display driver transistors, regulators etc.

73 m/4

W9GB
03-15-2008, 07:36 PM
Personally, I would start with my DVM to check if voltage is present for the display.
IF repair or benchwork is infrequent -- you may want to call AES or Avvid for professional guidance.

TS-850 Repair Page (great resource for the bench tech)
http://n6tr.jzap.com/850repair.html

===
Dead Display (from N6RA):

Thanks to KH6DV who pointed me in the right direction, I fixed my TS-850's dead display.

The problem was a bad 470 microfarad 16 volt electrolytic associated with an inverter that powers the LCD display. The cap leakage was not apparent until the cap was removed. In my case, the cap damaged a circuit board trace, so I also had to install a jumper. The damage to the trace was not visible, so it was hard to find. The damaged trace interrupted the power to the inverter.

Oddly, the cap (labeled C18 on my board) is not on the service manual schematic (page 173), but it is in the "pictures" on page 174.
For good measure, I replaced the other two electrolytics on the board (two 100 microfarad 16 volt electrolytic caps).
==

DK9IP has been collecting service information for the Kenwood TS-850
http://www.dk9ip.de/DK9IPdownload/TS850_IM/TS850_IM.html

Here is Instruciton Manual [Adobe Acrobat] (3.7 Mb)
http://www.qsl.net/dk9ip/850IM/850im.pdf

TS-850 notes
http://www.radiomods.co.nz/kenwood/kenwoodts850.html

w9gb

VE2NSM
03-15-2008, 07:59 PM
HA!

I had the same problem, if I remember properly, a leaky electrotlytic on the display board corroded a trace that supply voltage to the little "plasma" or neon illuminator.
Removed the cap, repaired the trace, put a new cap et "voilą" !

The broken trace was under the cap.

I don't know if it will be your case though.

AB9LZ
03-15-2008, 09:07 PM
Yep the 470uf cap was bad and had leaked, the trace looks OK though, hunting around for a replacement, you let you all know how it goes.

73 m/4

clif
03-15-2008, 10:21 PM
Think about it, If the trace were good the display would work.

Clif

AB9LZ
03-16-2008, 12:11 AM
Think about it, If the trace were good the display would work.

Clif

Right, it's just a decoupling cap, the trace indeed did break at the pad, new cap, jumper, all is well. Thanks guys.

73 m/4

VE2NSM
03-16-2008, 12:11 AM
Think about it, If the trace were good the display would work.

Clif

Exactly.

The trace has to be bad somewhere.

K5AR
03-16-2008, 12:59 AM
Yep the 470uf cap was bad and had leaked, the trace looks OK though, hunting around for a replacement, you let you all know how it goes.

73 m/4


My TS-850SAT had the exact problem with the LCD, glad you got it going.

VE2NSM
03-16-2008, 03:18 AM
Sounds like a common problem :D

K4TVE
09-27-2008, 09:52 PM
part of my 850 display blanks, but the meter section stays lit. i notice that this is serviced by a different chip. if the meter section stays lit, does that mean that i do not have the 470 uf electrolytic problem that i have been reading about in these posts?

thanks and 73
bill
k4tve

AB9LZ
09-27-2008, 11:44 PM
I've since had several other problems with that rig, all due to leaking electrolytics burning through underlying traces. Pop the lid off and start looking for obvious leakers, check the traces around every one of them.

73 m/4

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