Sanwa transmitter and futaba receiver will this work?
 

Sorry for the daft question but it's probably 15 years since I did this. I've got my old losi xx all wired up with a futaba 40mhz receiver in it. I always used a sanwa exces which I've found and charged up. First time I switched everything on the car went mad, thought it might be crystal related so found some new sanwa crystals and now the cars steering works but power is constantly on, trimmed it right back with no joy

Do I need to be using a sanwa receiver or is something else wrong?

I'm going to ask a load of daft questions so please forgive me if you know all this :blush:

Is the RX 40MHz FM? (I am assuming the TX is 40MHz FM)
Are the Crystals FM?
Is the RX just a standard 40MHz (not HRS or PCM?)
Rather than just altering the trim have you reset the end points on the speedo? Is the speedo brushless?

Cheers,

Ian

Reset the speedo maybe ?

No daft questions lads I'm a noob with this stuff

Receiver is this one doesn't say fm on it but assume it must be due it's age

http://m.ebay.co.uk/itm/FUTABA-R133F...-/400482526004

Both crystals say fm as does the module in the transmitter

Tried it in a car with a sanwa reciver and it does exactly the same :(

Not sure what PCM hrs mean

Speedo is brushed on old mtroniks pro digi rmx, it has a set button which stops the wheels turning but when I let go they start again. As it did the same in the other car I'm guessing it's not that

The sanwa exzes is a good radio I used them back in the day I know they were receiver fussy but futaba did work with them but use sanwa crystals only.
it don't sound like the radio is at fault more the speedo.
they pro digi was nick named the pro dodgy for a reason:)
try reseting the radio and speedo.
good luck.

is the throttle light on the speedo working? try re-setting everything and see if the throttle light is changing or lighting up when you move the throttle stick, if the steering is working, plug the speedo to the steering channel and the servo to the throttle channel, see if the servo moves on the throttle channel this will rule out the receiver;)

if it does work the servo ok on the throttle channel then its speedo, running full all the time is usually the brake fet blown in brushed speedos.... if you know how to use a dvm unsolder the motor and test from battery neg to motor neg, if it reads short then its brake fet in the speedo;)

hope this helps:)

Thanks will give that a try bit strange it does the same in 2 different cars I'm wondering if it's the transmitter

Running all the time can be caused by one of the forward drive FETs being blown as these switch the battery negative to the motor negative.

If the brake FET was blown short circuit (motor negative to motor positive, the forward FETs would get hot when throttle was applied because the blown FET would be shorting them out.

swapped the channels round and both the steering and throttle now work, light comes on the speedo etc etc. I think it maybe transmitter related, any ideas?

managed to stretch the receiver wires across to a car i know is working with a 27mhz receiver, and it does exactly the same with that car, so definitely not the speedo

If the brake FET was blown short circuit (motor negative to motor positive, the forward FETs would get hot when throttle was applied because the blown FET would be shorting them out.[/QUOTE]

sort of..... the brake fet sits between motor negitive and battery positive and is pulsed on the other leg to effectivly short the motor out to slow it down on braking....but they normally have a diode ( tekin, novak, m troniks did from memory) the brake fet can blow and short the diode and this gives it running constantly, it protects the forward fets....of course a shorted forward fet would do the same but i aint seen a forward one go as there is too many of them in parallel....it also depends how they blow....could go short on either side or could also blow open;)

yes light works....but car still runs all the time or the throttle is working as it should?

I am a bit lost here:lol: you know that this 27mhz receiver works......so how do you conclude it aint the speedo when it has the same fault?

Because the speedo was attached to the 27mhz receiver and radio and worked fine

When swapped round in current reciiever all seemed to be working but wheels weren't straight

And as another car does the same thing the only constant is the transmitter

with you now....hence the throttle question in my previous post;)

Any ideas what the issue could be with the transmitter?

interesting problem you have here..!

Do yourself a favour n bite the bullet! Go get yourself some modern gear.. buy a 2.4ghz set up n a cheap speedo and take it from there.. spurious equipment failure is a pain in the butt, n even if you get it working you will always have in your mind the fact that it once didn't work very well!! this is especially amusing if your car is heading straight for a marshal or a brick wall or disappearing into the distance at the time...

2.4ghz radio sets are available at a very reasonable price.. Spektrum 2.4ghz wheel type tx/rx sets on an auction site are going at 40 quid brand new.. you can even get lesser known brands at 30 quid or less..

A new mtronik brushed speedo is less than 20 quid.. or you can pick up some brushless systems for around 50 quid or less..

I mean these comments as helpful nothing more.. I once had a radio problem I thought I had cured and suffered the consequence..

I would say the pot has slipped in the transmitter, it could be something else but this can happen and is the most common cause:) i'v seen it on the sanwa super exzes and repaired it no problem

Ok thanks guys