LO and RF Hardware/Firmware Failures (300 to 399)

YTO Loop Errors (300 to 301)

These errors often require troubleshooting the Al4 Frequency Control assembly (Synthesizer Section) or the ADC circuits.

300 YTO UNLK YTO (1st LO) Loopis unlocked. The ADC measures YTO-ERR voltage under phase-lock condition.

301 YTO UNLK YTO Loop is unlocked. Same as ERR 300 except ERR 301 is set if the voltage is outside certain limits.

Roller PLL Errors (302 to 316)

These errors indicate a faulty roller oscillator on the Al4 Frequency Control assembly. Refer to Chapter 10. The A3 Interface ADC circuits may also be faulty. If error codes 333 and 499 are present, suspect the 10 MHz Reference, the A21 OCXO, or on the Al5 assembly (Option 103).

302 OFF UNLK Offset roller oscillator PLL is unlocked. May indicate loss of 10 MHz reference. The 10 MHz reference should measure greater than -7 dBm at A15J303. The ADC measures OFFSENSE at the beginning of each sweep and, if the voltage is outside certain limits, the offset oscillator pretuned DAC is adjusted to bring OFFSENSE within the proper range. ERR 302 is set if this cannot be accomplished.

303 XFR UNLK Transfer roller oscillator PLL is unlocked. May indicate loss of 10 MHz reference. The 10 MHz reference should measure greater than -7 dBm at A155303. The ADC measures XFRSENSE at the beginning of each sweep and, if the voltage is outside certain limits, the transfer oscillator pretuned DAC is adjusted to bring XFRSENSE within the proper range. ERR 303 is set if this cannot be accomplished.

304 ROL UNLK Main roller oscillator PLL is unlocked. May indicate loss of 10 MHz reference. The 10 MHz reference should measure greater than -7 dBm at A15J303. The ADC measures MAINSENSE at the beginning of each sweep and, if the voltage is outside certain limits, the main roller pretune DAC is adjusted to bring OFFSENSE within the proper range. ERR 304 is set if this cannot be accomplished.

305 FREQ ACC Unable to adjust MAINSENSE close to 0 volts using the coarse adjust DAC. The coarse adjust and fine adjust DAC are used together to set MAINSENSE to 0 volts with the loop opened. ERR 305 is set if the coarse adjust DAC cannot bring MAINSENSE close enough to 0 volts for the fine adjust DAC to bring MAINSENSE to exactly 0 volts.

306 FREQ ACC Unable to adjust MAINSENSE to 0 volts using the fine adjust DAC. The coarse adjust and fine adjust DAC are used together to set MAINSENSE to 0 volts with the loop opened. ERR 306 is set if the fine adjust DAC cannot bring MAINSENSE to 0 volts.

6-18 General Troubleshooting