[Kenwood] TS-50S Problem on LCD Board- Resistive runs-Update

[Don]

I removed the PCB from the front panel housing and I did locate L1 and L2.
Once I saw their location on the top side of the board, I found they are
marked on the manual layout. I just overlooked them. Now to find the
resistive trace and try to determine if the current is excessive causing the
vias to turn black.

Don  AF4Z 

-----Original Message-----
From: kenwood-bounces at mailman.qth.net
[mailto:kenwood-bounces at mailman.qth.net] On Behalf Of Don
Sent: Thursday, June 10, 2010 8:46 PM
To: Kenwood at mailman.qth.net
Subject: [Kenwood] TS-50S Problem on LCD Board- Resistive runs


Some time back I posted a note about my TS-50S have a problem with the
display and audio being slow to come on. It still has the problem but I have
isolated what I believe is the cause on the LCD Board. I have determined
that the 5V Supply from Connector CN1 pin 7 on page 29/30 of the service
manual is normal at C1 but not at C3. At C3, the voltage measures only
3.1VDC in RX and 2.5VDC in TX and this voltage goes to the display driver IC
as well and other components. My first thought was L1 is bad or a cold
solder joint. With a microscope, I can see some of the via that are in the
area have blackened as if they have got hot. In looking in the manual's
board layout on page 28 and on the board itself, there does not appear the
be an L1 or L2. Did Kenwood omit these parts after the schematic was
generated? I looked for the parts list of the LCD board but it appears to
have been omitted in the service manual. All the other major boards have
parts lists. Has anyone else seen the black via problem with their rig. I
guess my next step is to remove the PCB from the case and trace the runs to
see if there is an L1 and L2 and to find where the trace is resistive. Can
anyone provide any other history on L1 and L2 on the LCD board? Thanks,  Don
AF4Z

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