High power XPR4550 maxed out at ~20 watts
Posted: Fri Jun 02, 2017 11:45 am
Hi. I have a few questions about my 403-470 XPR4550. It's a 20-40 watt model, but I've never been able to adjust it beyond 20-22 watts. The model number as seen in CPS and on the sticker indicate it's the 20-40 watt model.
The PA bias current is set correctly. One thing I find suspicious is that TUNER won't accept the correct measured wattage readings I enter in the softpots. For example, a given softpot value might be set for 20.xx watts, but I measure only 17.xx watts. I am able to lower the values but only by a few hundred milliwatts -- not enough to be correct. After taking and entering measurements, attempting to WRITE to the radio using TUNER displays a message that my entered value(s) are out of range. I have no choice but to re-enter original values.
The radio otherwise performs as it should. On-frequency with good deviation. On a side note, the radio had a much older firmware version. I figured it couldn't hurt to upgrade it to the latest (R1.12.x), and though the upgrade went smoothly, it didn't have any effect on the transmit power issue. I'm out of ideas as to what might be wrong, so I'm wondering if my P.A. is defective. If so, does anyone have any experience or tips replacing the P.A. transistor on these radios?
Any suggestions will be appreciated.
Thanks,
Norman
W6OG
The PA bias current is set correctly. One thing I find suspicious is that TUNER won't accept the correct measured wattage readings I enter in the softpots. For example, a given softpot value might be set for 20.xx watts, but I measure only 17.xx watts. I am able to lower the values but only by a few hundred milliwatts -- not enough to be correct. After taking and entering measurements, attempting to WRITE to the radio using TUNER displays a message that my entered value(s) are out of range. I have no choice but to re-enter original values.
The radio otherwise performs as it should. On-frequency with good deviation. On a side note, the radio had a much older firmware version. I figured it couldn't hurt to upgrade it to the latest (R1.12.x), and though the upgrade went smoothly, it didn't have any effect on the transmit power issue. I'm out of ideas as to what might be wrong, so I'm wondering if my P.A. is defective. If so, does anyone have any experience or tips replacing the P.A. transistor on these radios?
Any suggestions will be appreciated.
Thanks,
Norman
W6OG