Technical, Techniques, Hints, and Tips > Radio Equipment
Digifleet FM Tx service manual
scimitarjohn:
I've just bought this Tx unseen (big mistake) in a bad state, I can fix the cosmetics but the circuit board is a tad corroded (again fixable) but a couple of wires are hanging off the board so want to be sure where to refit! I love Digifleet gear, I've had an AM set from new (yes, I'm and old geezer) I use this with my steam launch[/size]. I[/size] bought this FM Tx to convert to 2.4GHz, it was cheap but I really don't want to throw it away and would like the project.
HMS Invisible:
Here I'll expand on what I wrote weeks ago (link) by saying the one I have beside me and in the attached photo looks the same vintage as yours and is from mid 1984. There are so many variants and board versions.
The basic Fleet circuit architecture was unitary gain inverting opamps (LM 324 with 33k resistors) handling servo reverse, span, mixing then feeding four of the encoder inputs. Three decades ago I drew a full circuit for my own reference but the basics are retained in my head.
I can't help you with a service manual but I'll give you a link to the encoder datasheet and reference to the 2.4 GHz module for connection. Fleet was return-to-base and working from his attic or kitchen table. Service agent? {-)
Just a decent photo or two from you is all the boat club electronic slaves need to say what the wires are for on the stopwatch.
NE5044 data is here https://www.alldatasheet.com/datasheet-pdf/pdf/17948/PHILIPS/NE5044.html
I likely don't know you John. If you were J.B. of Gravesend-Chantry I'd draw you a circuit from photo or do any repair or conversion or swap with this pristine 35MHz after rejuving the NiCd and putting in a 2.4G module.
scimitarjohn:
Hi, very much like mine but tad better nick. Have taken some photos and will send them just as soon as I find out where my grandsons put the cameras download cable! Many thanks John
HMS Invisible:
Your camera may have Bluetooth wireless even if it has mini USB and certain to do so if it has hdmi.
Beforehand, what I guess about the wires:
A photo of both sides of the printed circuit is what is of interest. If the loose cables are not battery, or added charge wires for battery or a connection a missing din style trainer/charge it may be one of the channel inputs or a switch to one of them like the switch that connects two throttles to one stick.
Four channel controls go to the LM324 via 33k resistors. Extra up to number seven go via resistor networks to the encoder as per datasheet.
A previous attempt to a 2.4G module will trace through components to the dil encoder chip output ppm.
scimitarjohn:
Hi, all OK, wife had put lead 'somewhere safe!'. It's probably a lot simpler than you suspect. The loose black wire is negative from the battery pack and the loose white wire is from the middle contact on the ON/OFF switch. I've attached photos, your PCB looks very similar, a tad newer and certainly in better condition than mine. Oh, and while I'm asking, if I get it powered up I can check around with a scope but it would save some trouble if you know where to pick off the pulse train for the 2.4 module. Sorry photos not working, message come up - 'message field left blank' ??
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