Progress update on Futaba to Jeti migration for a larger jet...

Based on feedback from Wayne, Danny and others, the hybrid PSS 2018/CB200 setup, while it worked fine, was seen as a bit of a kludge. I have to agree.

So I decided to go more "native Jeti" and put a CB400 into the plane. But I wanted to still hang on to the nice Sbus Emcotec wiring and connectors.

For the tail, I placed a CB100 "satellite" in the tail area. Since there is only one servo in each elevator half and in the fin, I was able to keep the Emcotec connectors and just solder up an adapter to go into the servo outputs of the CB100. I arranged the wiring at the CB400 to send the EXBus on the white wire of the former Sbus feed, and took power and ground from one of the BEC outputs on the CB400. The spec says they are good for 6A. So this is a nice clean setup. 6A should be plenty for the rudder and elevator. In-flight telemetry from the CB100 is confirming this.

For the wings, I have two servos (ail and flp), thru one Emcotec connector, classic Sbus. So i could replicate the tail setup with a CB100 in each wing as the Esprittech video did. But instead I used the SlinkE device that converts EXBus to Sbus (https://www.rconix.com/collections/s-bus-converters). Very nice device (and a very nice guy too!).

The SlinkE feeds the white/signal wire of the wing connectors. That left me with one BEC output open and I was concerned from prior measurements that 6A would be marginal for the two flaps. I've set telemetry alarms on 4A draw for each battery (from the CB400 telemetry signals) and it's actually interesting/slightly alarming how often this triggers in flight .. which means a total of 8A being drawn... yikes!

Since I am trying to be a good Jeti citizen, I had been reading the manual AND release notes on the CB400, and saw in a recent note that Jeti commented on the polyfuse devices in the CB400 possibly being tripped by high torque servos and explicitly contradicting the manual, they recommended paralleling power and ground (but of course not signal) from multiple servo outputs on the CB400 (up to 8 they said!) to gain additional current drive capability for high-draw servos. I know a little about polyfuses, and let's just say using them in parallel is controversial, but I went ahead anyway based on Jeti's recommendations.

So what I have is a parallel connection of three servo power + grounds from three CB400 outputs, that feeds the red + black (power) wires .. for each wing .. and white/signal wires fed by the Sbus output generated by the SlinkE device. This then routes thru the standard Sbus wiring to the wing and its one connector. Channel numbers on the Jeti and EXbus were purposely set up to be the same as on the Futaba Sbus system.

The two Rx's connect to the Cortex pro, the Cortex connects to the two primary 2.4GHz inputs on the CB400, and the 900MHz to its CB400 input as recommended by Jeti.

Net: much simpler, much cleaner system, all works exactly as I hoped.

For others doing PSS/DPSI 2018 conversions, I think if all you want to do is two 2.4GHz Rx's and a Cortex or Cortex Pro, then it's easy to keep the 2018. It really was the proper integration of the 900MHz that drove all the complexity with the 2018 setup. But to me the 900MHz backup is a major reason to use Jeti so to convert without it seemed like a waste of time.

I do have some more work to do to characterize the multiple parallel polyfuses and make sure I know how they really operate ... I've got a stack of power resistors on hand to do the testing and once I have the work done, I'll report back. I could not find a specific spec on the polyfuses used in the CB400 but I am guessing approx 4A. If anyone knows more, please let me know.

The only irritating issue left: I setup the remote on/off with the RF switch for the CB400. (I added one of the locking switches to the TX as recommended). Jeti gives a spec for the current draw with the CB400 in this configuration when turned off (140 uA) .. but I see MUCH larger current draw than that, and it is draining my RX packs in a few days .. so I am realistically going to have to unplug the batteries between flying sessions which really limits the attractiveness of the remote on/off. If it really met the 140 uA spec, which would take about 2 yrs to drain a 2.3Ah battery .. so something is up. I'll be checking into this. Again, if anyone knows more, I am all ears... My current theory is that the R3/RSW does not come close to meeting the 140uA spec .. Jeti must be referring to what happens with the magnetic switch or perhaps some other RF switch. If that's the case, then I can just switch off the R3/RSW instead of actually unplugging the batteries...

Oh .. one more thing .. given all the questions I have about individual servo current draw, I am really interested to know if/when we will have Ditex servo capability in the CB400. ZB's original postings suggested this was coming but unless I missed it in the CB400 release notes it's not out yet. Only the RX support it for directly-connected servos. I humbly submit that this is cute but useless .. if you were worried about these measurements you would not have servos connecting direct to an RX!

(sorry for all the posts! catching up after travelling!)
Dave