Batboard

I have a UHF CDM1550LS+ that I received, at first there was no audio out of the speaker.(I receive 5 of these, was warned 1 had no audio out, that's how they used it). I thought at first the speaker was just unplugged, but was wrong. I got digging further and when I flipped over the board I found 1 component,I believe to be the audio processor, had 1 leg that was gone and it looked like the component was burnt. I then tried to solder a lead from the pad to the processor. When I reassembled the radio would not turn on.

The component that I am referring too, if you flip the board over, it is on the right side(front facing you), and has 6 or so legs coming off one side. It also has heatsink compound on it as well. From left to right, it was the 3rd leg in, with the legs looking at you.

I'm not sure if I damaged the processor in the process of soldering or if there was a short in it and it blew the fuse. I am not familiar with this series of radio and do not have a service manual.

I was going to just buy and replace the component and see if that fixed it. I hope someone here can help me fix this without spending a lot of money.

This has become a nightmare of a deal that I got into and just trying to make the customer happy.


Jordan.

I see a 5-pin device as you described.

U0641 Mot# 5183308X01 Description LM2941

http://www.ti.com/lit/ds/symlink/lm2941.pdf


Theory of operation from the manual:

The DC power distribution throughout the radio board is shown in Figure 3-2. Voltage regulation for
the controller is provided by 4 separate devices; U0651 (MC78M05) 5V, U0641 (LM2941) 9.3V,
U0611 (LM2941) SWB+ limited to 16.5V and VSTBY 5V (a combination of R0621 and VR0621). An
additional 5V regulator is located on the RF section.

The DC voltage applied to connector J0601 supplies power directly to the electronic on/off control,
RF power amplifier, 16.5V limiter, 9.3V regulator, Audio PA and 5.6V stabilization circuit. The 9.3V
regulator (U0641) supplies power to the 5V regulator (U0651) and the 6V voltage divider Q0681.

Regulator U0641 is used to generate the 9.3 volts required by some audio circuits, the RF circuitry
and power control circuitry. Input and output capacitors (C0641 and C0644 / C0645) are used to
reduce high frequency noise. R0642 / R0643 set the output voltage of the regulator. If the voltage at
pin 1 is greater than 1.3 volts the regulator output decreases and if the voltage is less than 1.3 volts
the regulator output increases. This regulator output is electronically enabled by a 0 volt signal on
pin 2. Q0661, Q0641 and R0641 are used to disable the regulator when the radio is turned off.

From the trouble shooting guide under power up:

9.3V DC at Pin 5 of U0641? No? Check U0641, Q0641, Q0661, D0660 & D0661