Hello,
I have a question and problem regarding my 5645MG and 5955 servos. Here is my setup:

Wild Hare 28% extra 300
Futaba FP-R138DP PCM 7 channel receiver
Here are my connections on the receiver:

Battery slot: 6 volt NiMh pack
slot 1: Left aileron HS-5645MG x1
slot 2: both elevators on wye harness -HS-5645MG x2 with one servo reversed using programmer
slot 3: HS-322 on throttle
slot 4: rudder 5955-TG
slot 5: HS-322 on choke with wye harness and second 6volt Nimh battery pack
slot 6: right aileron HS-5645mg x1
slot 7: sullivan skywriter smoke pump

Here are my problems:
1) the elevators won't work together on a wye harness. As mentioned above, I have two 5645's on the elevator halves. They were both puchased from tower at the same time. One elevator I had reversed with a hitec programmer at the LHS. Each individual servo will work on their own, but they won't work at all when I connect them with a wye harness together. Any thoughts?

2) this problem is related to the 5955 on the rudder. With power on, the servo emits a constant humm, that is fairly loud. There is no twitching or anything like that, just a loud humm. Is this normal?

There was some revision v1.04 servos released that would not work in multiples driven from a single channel source with Futaba PCM. Sounds like you have two of these servos.

I'd suggest you send the servos to Hitec Service for a component update to eliminate the OEM compatibility issue that was later realized and resolved. Or you could drive them elevator halves individually with separate channels and a mix, BUT you’re limited to seven channels with your RX. Or you can use a wye which is boosted and or amplified, this wye will isolate the servos from one another, this is the least desirable IMO.

There is no charge to update your servos. Simply include information with regard to your problem, ask them to update the software and perform the component upgrade for Futaba applications. Don’t forget to mention one servo needs to be reversed.

The 5995TG maybe reacting to noise or simply working as designed, premium digitals tend to buzzz-chater-beep when loaded. Try and remove the servo arm note if the servo still chatters, make sure there is no binding and the static load is minimal at neutral. You might even remove all the other servos from the RX and note if the noise your hearing is still present and being caused by some sort of electrical feedback.

thanks for the great explanation. I will try all those measures you mention and probably will send the servos in to Hitec. The best option, IMO, is to obtain an 8 channel PCM receiver and use different channels for the elevators, but I will try the update first.