Mode Zero

The last of my recently acquired Tx's:

World Engines England Blue Max
This is a black vinyl clad Tx based, as far as I know, on the similar US World Engines Tx. There are 4 channels wired up, but you can see in the pictures that there are slots cut in the top of the ali case for 2 x additional pots for extra channels. Apart from needing a good clean, and a little bit of the vinyl peeling in a corner, it appears to be in good shape.
Next is a Royal Tech R/C Tx:
This is just a case & hardware, the electronics having been removed at some stage. Of note is that the stick pots only use 2-wires, with a jumper spanning from the wiper to the other end of the pot track. This Tx definitely needs a good clean The holes and one slot left open suggest that it probably had at least another 2 channels at some stage. The Tx uses D&R stick units. Personally, I have found these sticks to be very nice to use. Does anybody know what encoder the Royal tx's used? I suspect it may have used an early IC type encoder. I'm considering using either Phil's 7ch encoder or Mike's F3A variant.


The last Tx is a Sankyo Digital:

Now, this one really does need a good clean It appears to be a 5 channel set with the 5th channel being a retractable undercarriage style switched channel.

In contrast to the outside, the inside is nice & clean. The PCB is immaculate.
That wraps up the Tx's I've come into possession of - thanks Barry

As I do the conversions, I'll post details. I've currently got 3 of Phil's FHSS rx's and 2 encoders doing soak testing on the bench. These are such a great alternative, cheap as chips and ideal for several of these Txs. There is also Tobe's Tx board which accommodates either encoder software and will drive either the NRF24+ RF module or one of my Frsky hack modules. Spoilt for choice

oops - hit the submit button by mistake

Mike - please delete

The First Restoration - The Royal Tech R/C

OK, the first Tx out of the chop shop is the Royal. As reported earlier, it came minus any electronics, just being a case with D&R sticks. Contrary to what I wrote (in error) in the previous post on this Tx, the stick pots use 3 wires while the trim pots only use 2-wires.

First job was to strip everything and give it all a good clean using the spray degreaser I posted details of previously viewtopic.php?p=11623#p11623 . Sticks: The stick pots were all checked - none had any noticeable wear on the Bourne pots, which were all lubricated, and the wipers had no tell-tale silver wear marks on the whiskers either. I re-wired the separate trim pots and main control pots through a conventional 3 pin servo connector, then checked all of them for correct operation with a multimeter.

Encoder I used Tobe's terrific encoder board in the Royal Tx, running Phil's FHSS code - A full NRF24L01 FHSS Single Channel outfit -viewtopic.php?f=42&t=968 . Phil's original code is 4 channel, but with help from Tobe, I was able to get it to 6 channels, with ch.5 a 5k rotary pot and ch.6 a 2-position switch.

On the version of Tobe's encoder board that I have, there is a bank of DIP switches across D0 - D8. In Phil's code, D8 is used for calibrations and for the single channel button. Consequently, I wired a 3 pin header across the D8 DIP switch to connect the single channel button to - crude, but works a treat.

I followed up with Tobe and he advised me:
You could have used D0 as there is a pin header for it. In my updated board D8 D7 D6 and D5 have pin headers parallel to the Dip switch, .... and you just swap the position of what you like on a separate button/extension ... Be well, Tobe So, I now know better for next time

The S/C button is a tactile micro pushbutton soldered to a piece of board with a fly lead back to the main encoder board I'm very happy with the finished product. Power is 2 x 18650 cells, giving heaps of capacity. A zener and resistor on the original meter give me battery voltage. Next step is to fly it

Nice job , hat off!
Just a quick note, the board has a 3.3V regulator with all the necessary capacitors as recommended in earlier posts by Phil so, if I'm guessing right what you have behind the shrink is probably not necessary if you are using the shielded version of the nRF2401+
Once again very well done.

Tobe wrote: 12 Sep 2021, 08:54 Nice job , hat off!
Just a quick note, the board has a 3.3V regulator with all the necessary capacitors as recommended in earlier posts by Phil so, if I'm guessing right what you have behind the shrink is probably not necessary if you are using the shielded version of the nRF2401+
Once again very well done.

Thanks Tobe,

Your right of course - I did fit the little 3.3v reg. I actually assembled several RF units, shielded & un-shielded, ready for use with both your boards & my home-assembled versions (on perf-board), such as in my Futaba "bench Tx". All were intended to be powered from Vin, hence the use of the regulator. It's a learning process & sometimes I am really sloooow

Sankyo Tx - The next conversion out of the Kiwi branch of my Retrobate Chop Shop

Cleaning:
The Sanyo tx was the dirtiest, grubbiest tx I think I've ever seen "in the flesh" . So, the first task was to pull everything out of the case so that I could give the case a proper clean. Spray on the cleaner, let it soak a few minutes, then attack it with a tooth brush, then rinse clean with water. Repeat twice and voila Sticks
The stick assemblies presented several challenges. The tx came on mode 1, but I usually fly mode 2. However, the stick assemblies are asymmetric so swapping sticks from one side to the other also needed the sticks to be rotated 90deg. This wasn't a problem for the right stick (rudder & elevator became elevator & aileron respectively, all self centering) but put the (old) ratcheted throttle axis on the rudder function and the former aileron axis became the throttle. Swapping the spring centering required a complete dis-assembly of the stick mechanism,
a task that didn't go well
Both sticks had broken plastic pieces - brittle with age - previously repaired with CA. Like sand in your cozies, the CA had made its way into places it should not have! Consequently, undoing grub screws, pot nuts & screws took time, patience (most of the time) & an essential dose of verbal encouragement. Perseverance paid off in the end - both sticks + trims work freely, pot resistances measure correctly, the throttle function is now on the correct axis and the sticks are back in the case. Next step - the encoder.

Sankyo tx (cont.) Encoder:

I decided to go with another 6ch version of Phil's FHSS encoder, this time assembled on vero-board. The combination of encoder and RF stage made the best use of some bits in hand as well as some subassemblies already made, tested & "in stock". It also enabled me to make best use of the existing holes in the tx case!

I had to drill 2 holes in the case to secure the encoder on a 1mm thick plastic sheet - the plastic insulates the back of the encoder from the Tx case. The mounting holes are hidden behind the Sankyo Digital Tx label RF stage:
The encoder is coupled to an unshielded nrf+ module (one of those "in stock" items), mounted in one of Tobe's really neat 3D printed socket bases (viewtopic.php?p=8391#p8391). This insulates the module & antenna from the tx's metal case. I had to move the UHF antenna towards the back of the case to leave clearance between the RF module and the original battery meter. I couldn't shoe-horn anything into the vacant hole so I covered it with a name & phone number label. Tx power:
The original Tx had a 9.6v 8-cell AA NiCd battery, which was pretty much the standard for that era. In the Sankyo Tx, the battery pack is split into two packs mounted in a plastic housing fastened with screws to the bottom of the case. Each housing is meant to contain 4 x AA cells. I replaced the old leaking NiCds with 2000mah Enerloop NiMHs, but only used 6 cells, giving a nominal 7.6v. All power wiring was replaced. The 6-cell pack was wired to the existing DIN socket, using my 'personal standard' DIN wiring, which allows me to use the one DIN plug configuration to charge 2S, 3S and NiMH packs. A resistor in series with the meter provides an appropriate needle deflection, showing nominal voltage when the tx is switched on.

S/C Button:
I glued a small push-button into an existing hole in the case, rather than drill another hole. This push-button features a built in LED (not used) and is meant to be pcb mounted. Instead, I just hard wired a lead directly to a set of N.O. contacts. The lead then plugs onto the connector at encoder D2, for calibration and S/C operation. Fault Finding:
There is always something to challenge the grey matter (a euphemism for I always manage to stuff up and/or miss something!?!). This time, I had 2 challenges:

• While it all worked - i.e. move the stick & the servo moves - when I moved the aileron stick, both the aileron & elevator servos (Mode 2)
  moved in unison. The same happened when just the elevator stick was moved. Checked the mixer selections - both were off. Hmmm? Remove the encoder and check the wiring of the vero-board. All initially looked OK, but an ohm meter showed a short. When I used the most powerful magnifying loop I had, there appeared to be the tinniest of whiskers bridging between the A0 & A1 pins. Some careful & diligent scraping with a sharp blade resulted in a really tiny piece of solder dropping onto my finger and the ohm meter no longer showed a short.

• When I moved the aileron stick to the right, the servo moved to the right, but when I pressed and held 'right' (i.e. 1 press of the S/C button) the servo moved left. Grrrrr!! Swapping the positive and negative leads at the stick pot resolved that dilema.

Finishing Touches:
I keep a spreadsheet of the Mode Zero projects - Tx conversions or builds, Rx's, Pulse meters, etc. - that I've completed & when. I then nominally assign a "serial number" to each project, so I can affix a unique "manufacturer's label" if I so wish. The label is affixed to the bottom of the case. All in all, a great project and another Tx restored and ready for use