Why does the transmitter keep blowing fuses?

If the AC power supply board (SLP29910) is blowing fuses, the input power is hooked up incorrectly.

If the SPA or DMOD board is blowing fuses, do NOT replace the fuse and try again!!! There could be a problem causing the fuse to blow. Turn off input power and discharge the large blue capacitor to the left of the AC power supply board. Remove both the SPA and DMOD board from the transmitter. Using a multimeter, measure the resistance of the final transistors on both boards.

The SPA board should measure:

• Drain to Source is approximately 2.7 Meg ohms.
• Drain to Gate is approximately 2.7 Meg ohms.
• Source to Gate is approximately 5 ohms.

The DMOD board should measure:

• Drain to Source is approximately 130k ohms.
• Drain to Gate is approximately 130k ohms.
• Source to Gate is approximately 1.2k ohms.

If any of these measurements are significantly lower, the transistors will need to be replaced. It is best to replace both transistors at once versus one at a time.

For further trouble-shooting; refer to Section 2, Modulator and Power Amplifier sections in the Technical Manual.