Joe's Broken Golden Arrow

[JosephS]

I bought a broken golden arrow a while ago because it came with all of the original packing, manuals including the ni-cds and original charger.

I put some batteries in it.
It takes 6x AA batteries for the transmitter
4x AA for the car and 1 Tamiya plug 6 cell nicd

The controller is on channel 6 27.255Mhz

As advertised the car does not work, but in an interesting way, The controller powers on. The car will only power on with the 6 cell nicd attached.

I but batteries in it but used my 5 cell Nicd battery that I use for vintage and testing .
The steering works left and right full proportional.
The throttle only works full forward or full reverse and does so in response to the controller. There is no stop. Adjusting the throttle trim gets to where I can make it flip from forward to reverse, I can't coax it to a stop.

Importantly when I turn off the power to the car, the motor continues running in the last direction selected.

Does anyone know if this is an easy fix? Since the servo and radio appear working.

How do I test if a relay is working properly? Is there anything to check before I de-solder them?


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There is a wall of notes below.

I am going to guess that it is the motor driving circuit.

I found this excellent Spanish language website
https://reparar-cochesrc.blogspot.com/p/averias-y-preguntas-frecuentes.html

This page is devoted to older toy grade RC and how each component works. I found this schematic on the page

I was going to guess that the relay was bad, they seems to be working, switching between forward and reverse. So maybe the circuit that drives the relay in having this issue?

The circuit was also shown this way( or this may be from a different board)


the relay is described as

On the electronic plate of the Dictator, the two relays are type H500S03-2-C or MR301-3HS with 3 volt coil and resistance of 25 ohms. The coils are in parallel, so if we measure on the plate it would be about 12.5 ohms. There is a transient suppression diode in parallel with the coils.

I found an image online of a golder arrow receiver board

showing the NEC MR301-3HS relay.

[JosephS]

Tutorial on how to test a relay with a multimeter
https://www.etechnophiles.com/test-relay-with-multimeter/

[Dadio]

I don't know much of these but I fixed one of these type boards for a friend by going over all the solder points on the board with a reflow gun but you could just touch then up with a soldering iron , these old boards were usually pretty robust in the components but suffered from dry solder joints .

[JosephS]

Thought I would see if I can make this work.

I think the buz11a fets I got for my Novak repairs might work to replace the ones on the board. I also found some cheap relays that look like that may work.



I’m taking some photos in case I break a wire off the board

Wire

Black - antenna
Pink -power switch
Brown- power switch

Orange- servo
Black - servo

White- aa battery box to power switch
Blue- aa battery box to board

Green -servo
White -servo
Blue-servo
Yellow- servo

Thick
Blue-motor
White-motor
Black -battery
Black-shunt wire between relays
Red battery

[JosephS]

Someone on the internet had the same trouble as me on

https://forum.digikey.com/t/nec-n8700-to-220-transistor-cross/7978/6


They used this one and reported getting the device to work.

I’ll see how much that overlaps with the devices I have.

First going to test the device again before I tear it down and make sure it’s not working

[JosephS]

Looking at the bottom of the circuit board there is an obviously broken trace near the motor white wire on the board

[TRX-1-3]

Looking at the bottom of the circuit board there is an obviously broken trace near the motor white wire on the board

Can broken traces be repaired?

[Frankentruck]

Looking at the bottom of the circuit board there is an obviously broken trace near the motor white wire on the board

Can broken traces be repaired?

A wire could be soldered to each side as a jumper to bridge offer the damaged area.

[1911Colt]

I would cut away the bits of trace that have lifted off the board, and run a wire from the solder connections on either side of the break.

[JosephS]

I would cut away the bits of trace that have lifted off the board, and run a wire from the solder connections on either side of the break.

I just found 2 components that were on the trace a a soldered a small wire between them.

That didn’t work. I pulled the board from the car and will replace with some general purpose hobby gear.

I may try and find a am 27?mhz radio to use the original transmitter , but I don’t want to spend much at all on this car.

[juicedcoupe]

I may try and find a am 27?mhz radio to use the original transmitter , but I don’t want to spend much at all on this car.

Even though they are 27mhz, most toy grade and hobby grade electronics aren't compatible. They usually just cause interference with each other.

[JosephS]

I may try and find a am 27?mhz radio to use the original transmitter , but I don’t want to spend much at all on this car.

Even though they are 27mhz, most toy grade and hobby grade electronics aren't compatible. They usually just cause interference with each other.

For now I am just going with a flysky setup and some old speed controllers to get this working.

I have heard that the fully proportional tyco radios are compatible with hobby grade gear and the right crystals.