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Author Topic: TS-790 dim sub rx display  (Read 3946 times)
WB8PFZ
Member

Posts: 201




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« on: June 07, 2015, 04:43:45 AM »

Is this caused by a bad light bulb? I have looked on line and can not find info. Thanks Mike
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W9GB
Member

Posts: 3148




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« Reply #1 on: June 07, 2015, 07:28:02 AM »

Quote from: WB8PFZ
I have looked on-line and can not find info.
Good bench technicians, go to the Service Manual for these answers.

Internet Q&A / advice postings are a mixed bag, from snake-oil salesmen
to solid-advice from qualified techs with references
to the SOURCE information (OEM manuals; bench experience; mfg. training for that radio).

Kenwood TS-790A/E Service Manual
SADLY, many of these Scanned versions, OMIT the original large fold-out schematics
http://www.ko4bb.com/manuals/50.158.136.69/Kenwood_TS-790.pdf

PAGE 120 - Disassembly of Main parts.
Sub-Rx display (LCD) is a separate module (19)
Back-lighting by LED or Incadescent Bulb of an LCD is common. These can and do fail.

PAGE 68 --- PARTS LIST
====
(LCD) - INCADESCENT LAMP: B30-0866-08 : 12 Volt, 100 mA [Main Display??]
(2C) - INCADESCENT LAMP : B30-0817-15 : 14 Volt, 80 mA [S-meter, Sub-Rx lamps]
Lamp size is not indicated, BUT T-1 is a common size for Japanese radios.
====
Kenwood Parts
http://www.kenwoodparts.com/index.php?kwparts_Session=33fd38af7a7205651fc767076b3ead2a

Desire to Talk to a good Kenwood Tech?  
CALL or e-Mail --- Clif Holland, KA5IPF at AVVID (Mabank, Texas)
http://www.avvid.com
« Last Edit: June 07, 2015, 10:15:49 AM by W9GB » Logged
W9GB
Member

Posts: 3148




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« Reply #2 on: June 07, 2015, 10:14:31 AM »

The fact that the Sub-Rx display is DIM, you likely lost one of tbe 1 lamps for backlighting.
Change BOTH lamps.
===
Clif Holland's advice about TS-790 Sub-Rx Display on June 29, 2010 here on eHam.net
http://www.eham.net/ehamforum/smf/index.php?topic=69276.0

With the style of sub-display used on the Kenwood TS-790, when the bulbs go out the display is unreadable.
A flashlight, as you found out, will show the display is working.

The Sub-Rx uses TWO incadescent lamps for LCD backlighting.
Round up two 14 Volt, 50-80mA grain of wheat bulbs and fix it.
Tilt the front display over and there they are.


-- Clif, KA5IPF
« Last Edit: June 07, 2015, 10:06:37 PM by W9GB » Logged
KA4POL
Member

Posts: 2409




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« Reply #3 on: June 07, 2015, 10:13:21 PM »

As you got to repair it anyway, consider exchanging the incandescent lamps by LEDs. You'll need a resistor in series to reduce the voltage according to the selected LED. LEDs will not deteriorate if you follow the specs.
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W9GB
Member

Posts: 3148




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« Reply #4 on: October 30, 2017, 05:30:49 PM »

M1ABK recorded repair of sub-Rx display : burned out backlight bulbs.
http://m1abk.blogspot.com/2016/10/ts-790-repair.html
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