Info : Illumination of TK-760H

[stangmansvo]

Hello everyone !
Need some info on how easy it might be to repair the illumination of the digital display. The light is out now in our rescue unit's radio.
Thanks & Merry Christmas to all
steve

[k2hz]

I don't have a manual for the 760H but if it is the same as the 760G here is what to look for:

The illumination of the LCD and the keys is controlled by the shift register IC510. If IC510 MBL is high it turns on Q506 which both turns on Q505 to light the key backlight LEDs and also applies a voltage to the MBL pin on J501/CN501 connector. This is the connection to the display board and lights the LEDs D802-D805 above the LCD display.

If both all the key and LCD illumination is off, it would likely be a bad IC510 or Q506. If the keys are lit but all 4 LEDs that illuminate the LCD display are out, I would suspect a bad connection at J501/CN501 or damage to the MBL line somewhere on a circuit board.

First step would be to check for voltage on the MBL pin of J501.

If the LCD is partially lit and only one or two of the four illumination LEDs is out then it may be a bad LED. Very unlikely for all 4 LEDs to fail.

[stangmansvo]

Hi all
Thanks for the info !

ALSO< just found one TK760 with the lights flashing on and off !
Wow must be gimmets in these radios !!!!!
steve

[westcoaster]

Hi all
Thanks for the info !

ALSO< just found one TK760 with the lights flashing on and off !
Wow must be gimmets in these radios !!!!!
steve

We had one 760h with all led's flashing. it went on for a short time then stopped. with no light. I would be interested in finding out where to look to repair this...

[stangmansvo]

Hi all

Anyone have info on repairing the illumination on these radios ?
Have several that went dark. Letters & Numbers are ok just the back lighting.......
steve

[Wes]

This is a common problem with the older 60 series mobiles.

There are 3 surface mount LED/Bulbs, (not sure exactly what they are), anyway there are 3 on each end of the display. They are connected in series and if one does out, they all go out. Sometimes one end of the display lights will go out and the other will still be lit. The flashing on and off most of the time is the surface mount bulbs loosing connection to the display circut board. Sometimes the bulbs will not be burned out and only need to be resoldered. You can actually ohm them out to see if they are bad or not.

Usually once you get it tore down, it is just as easy to go ahead and replace them since they are fairly inexpensive anyway. Because even if you have good bulbs, there is no way to know how much life is left in them.

We are an Authorized Kenwood Dealer and Service Center if anyone needs anything done, email me direct and I can get you a quote on the repair costs.

Hope this helps.

============================================

Wesley C. Hutchens (wch36@yahoo.com)
Field Technician/Sales/Service/Installation
Ra-Tech Services Wireless Communications
Mount Airy, NC

[stangmansvo]

thanks Wes

I will be in contact with you regarding this issue

steve wendling