Post Number: 15138
|Posted on Wednesday, January 23, 2008 - 9:39 pm: ||
The information below was given to me by Sam Lewis today: 01/23/2008 and he asked that I post it for the Copper Forum Member's.
This information below describes the modification required to reduce noise (motor boating) in some Magnum S9 radio's.
This ONLY applies to S9's that have the new TDA2003 audio power amplifier on the new PCBX-0717.
Which were about 150 radio's or less produced with this problem.
S9 Serial numbers: S003869 and higher will have the TDA2003 audio power amplifier.
To determine if your S9 radio needs this modification; look at the panel of the radio and verify that the serial numbwe tag or the revision tag (if installed) on the back of the radio does not have an "A" marked on it.
If so, then this revision has previously been done.
If there are NO markings to indicate that this modification has been done, verify you have the new TDA2003 audio power amplifier by removing Top and Bottom covers and with the component side up and the front of the radio facing towards you, look underneath the Echo/AMT board attached to the right side wall. If you can see a small (1" x 1") pc board mounted vertically to the motherboard, then you have a TDA2003 audio power amplifier.
If there is NOT a vertically mounting pc board underneath the Echo/AMT board then you have an older model, which does not require this modification.
With the TOP cover removed and the solder side facing up, see FIGURE 1.
Figure 1: Solder Side of Radio
Add a 220uF 16V capacitor positive side to the third pin from the edge and negative side to lead R4 on Backlight board.
See Figure 2.
Figure 2: Installing the 220uF Capacitor
After re-installing covers turn radio on and receive a signal on any channel, then verify it sounds ok.
Tune to an unused channel and maker sure squelch is Closed (quiet) and adjust volume control up and down.
No noticeable noise should be heard on the speaker.
Set volume to 12 0'clock and adjust the dimmer slide switch and verify no noticeable noise is present.
Re-install covers to radio and with a black pen/marker mark a capital "A" in the upper right hand corner of the serial number tag located on the back of the radio.