Microcontroller Troubleshooting; Deviation Problems - Shure SLX2 Service Manual

MICROCONTROLLER TROUBLESHOOTING

25A1090 (Rev.3)

DEVIATION PROBLEMS

If TR200 can't be adjusted to obtain proper deviation, try to isolate the problem to the Audio
or RF section. To check the RF section, set the transmitter frequency to the frequency listed in
Table 1.2 in Section IV and verify that the tuning voltage of the VCO is correct. To check the audio
section, apply -10dBu at 1kHz to TPA0. Set the gain to "0 dB". Check for audio with a scope at
TPA1. The level should be approximately 0dBu. Next, check the audio level at TPA2 for -0.8dBu.
Finally, check the level at pin 14 of IC150-4. If the level is correct, check the values of R504,
R510, R511, and C513-C5126 in the VCO area. If there is no audio, or the level is wrong, the
problem is in the audio section. Trace backwards through the audio stages until you find the prob-
lem.
This paragraph describes what digital signals need to be seen to have audio running through
a SLX system. The first thing that needs to be checked is, if the microcontroller is running its soft-
ware.
If you see numbers or only fragments of numbers on the display after the unit has powered
up, the microcontroller is running fine. Fragments of numbers in the display point to an open LCD
driver pin or an intermittent LCD panel connection.
To test the microcontroller for normal operation, please test the following pins and conditions.
Microcontroller Pin Number
Across 10 and 9
Across 20 and 21
Across 28 and 29
The turn on procedure of the SLX transmitters includes several stages:
T = 0.000s: The power is turned on (soft switch). 5V and 3.3V are established
approximately at the same time.
T = 0.480s: 32.768KHz crystal oscillates in a stable manner (~300ms) and internal reset
cycle (~180ms) is over. From now software gets executed.
T = 0.???s: Microcontroller pin 5 (RF_VCC_OFF) goes from 5V to 0V. Synthesizer is
powered on.
T = 0.???s: PLL data gets sent. You should see a signal similar to the graphic on an oscilloscope.
1 to gnd
4 to gnd
VDD and VSS
VDDAD and
31 to gnd
29
Net Name Condition
~RST 3.3V
~IRQ 3.3V
3.3V
3.1V
VSSAD
VDDA and 3.3V
VSSA
OSC2 Square Wave
f0=32768Hz