Table 6-2: Diagnostic Leds - Tektronix SPG 422 Service Manual

Diagnostic LEDs
Table 6–2: Diagnostic LEDs
Board LED Indication
Digital DS1 Oven Under Temperature
Digital DS4 13.5 Loop Unlocked
Digital DS2 108 Loop Unlocked
Digital DS3 6.144 Loop Unlocked
Front-Panel Diagnostics
S1 Diagnostic Switch
SPG 422 Service Manual (B034000 and above)
There are several Diagnostic LEDs on the circuit boards that only light in the
event of a problem within a given circuit. See Table 6–2 below for the LEDs and
what problems they indicate.
Solution
Wait at least twenty minutes after power-on to assure that the crystal is
warm and stable. This LED could be on by itself or all of the other
LEDs could also be on.
If on in conjunction with DS1, Oven Under Temperature LED, just wait
until the crystal warms up then both LEDs should turn off. Otherwise,
the crystal could be out of the range of the 13.5 PLL. If you are using
internal genlock, this LED should never be on.
The 108 PLL is outside of its 50 kHz pull-in range. If DS1 and DS4 are
also on, wait for the crystal to warm up before continuing troubleshoot-
ing. Otherwise, there is a problem in the 108 MHz oscillator circuit.
The 6.144 MHz audio clock is unlocked. There is a problem in the
6.144 MHz oscillator circuit or data is not properly loaded in the Ado
Altera part.
These are explained completely in the user manual. Please see the discussion of
the front-panel diagnostics in that manual.
These diagnostics are in addition to the front-panel diagnostics and can help
narrow down a problem.
There are three types of diagnostics, including:
C. Diagnostic runs continuously until switch is moved to new position
U. User feedback only (using LEDs, LCD display, scope display, etc.)
P. Processor feedback (using LCD display or RS-232)
Maintenance
6–9