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the EG2 pin on the control board. While operating the amplifier at full power, by rotating the LOAD knob, IG2 can be
varied and the screen voltage can be measured. This way the current limit of the screen regulator and the ig2 indicator on
the front panel can be checked quickly, without the need for a special load.
However, the amplifier has to be opened and wires used to extend the screen voltage connection to an external current
meter and volt meter.
17.1.7 IPTRIP ADJUSTMENT
Adjustment: POT6, marking: IP TRIP
This is the sensitivity of the high plate current protection (cut-off).
When the plate current exceeds the adjusted limit, even for a very short time, the start-up timer is reset. The screen
voltage is cut off and the FAULT light turns on. To make the FAULT light go off, the amplifier must be put on STANDBY. If
left on OPR, the operation will resume automatically at the end of the (about) 2 minutes warm-up time. During this time,
any RF power applied to the input is bypassed into antenna.
Connect a DC supply to pin TP2 on the control board (in the top corner). Negative to TP2, positive to the chassis.
With the amplifier powered and the READY light on, put the front panel switch on OPR.
Apply a current gradually increasing from zero and check that the protection is triggered at about 2.5 A of current. When
this happens, the FAULT light will turn on.
If the current value found is much different from 2.5 A, adjust POT6.
To repeat the adjustment or checking, a waiting time of about 2 minutes is needed every time for the READY light to turn
on again.
To speed up, the resistor R20 (5.6 Mohm) can be paralleled briefly with a lower value resistor (1k – 100k). Touch R20
with, say 10 kohm in parallel and the Ready light will turn on immediately.
See picture below (Fig. 23) for the position of R20.
