Hi everyone,

I’m working on restoring a vintage Yonezawa Wild Champs (also known as Wave Hunter) from the 80s and could use some advice.

the problems is:
the front wheel turn right and left when i activate the remote => this is ok
but when i activate the remote to go foward / backward this does not work, sometimes the wheel start to roll with no reason briefly when i dont touch the remote,
so i thought it was a transistor problem i replaced them (see below) but it's still the same

What I’ve already replaced:

• Q1 was a C380 transistor, replaced with a C1815.
• Q2 and Q5 were 945P transistors, also replaced with C1815.
• Replaced the large capacitors (not sure of their original values, but they were visibly bulging).

Current status:

• The car powers on, but I’m still troubleshooting the motor and steering controls.
• I noticed that the white and blue wires seem to be connected to the rear motor (propulsion)

please find photo of the car

if you have any idea of what i could do next it would be very helpfull

best regards

this is the model :









remote inside

remote

main board of the car

main board of the car

hi,
I find out the back motor is controlled by a 10 pins LB1640 as seen on the this picture,

i tested the motor with a 9v battery and its ok, (the wire blue and white are the + and - of the motor)

so the problem is the LB1640 does not get what its need on IN1 or IN2

on the pics below i inverted the picture on the bottom to match the circuit on the top and try to find out the componants before IN1 and IN2 on the LB1640

Hello,

i continued to try to restore it,

i didn't find how to fix the old electronic circuit
so i replaced all with an ESP32-CAM and a L298N Motor Driver
and used a ps4 to control it with a ps4-eps32 code found on GitHub : aed3 PS4-esp32

it is working , but i have a lot of bluetooth deconnexion of the ps4 pad, not easy to fix

as someone who has dealt with vintage electronics you most likely have to replace every single capacitor as there is a good chance a few if not most probably dried out.
Seeing you changed a few out, but aren't sure if you got the values right that could cause a lot of issues for example if it uses a tank circuit for tuning where the cap value can drastically change the frequency it will receive. Even if you didn't change them out the caps drying out could cause the capacitance to change, and cause issues too.

as for the ESP cam losing bluetooth connection. I can only take 2 guesses first guess is the motor is causing interference with the BT radio signal. Best bet IMO would be put the antenna in the front as far from the motor as possible.

Another guess is it is a possibility if you are using AA's (it looks like you are using the original battery compartment) the batteries voltage might be dropping low and causing it to lose power in blips.

honestly easiest option IMO (especially if you happen to own a 3d printer just guessing by having esp's lying around ) just buy a cheap brushed 80a ESC(it could probably be 40a I just like being safe in these things), a cheap servo, and a cheap radio, and mod it. Most expensive part will be the radio which looking cheapest I see are $30 usd... I remember when they used to be $15 >.> total cost would be like $60 usd if you go cheapest.
Only real modification needed to be made would be to make a servo mount for the steering.

Hi,

Thanks for your answer!
I tested one last thing and just fixed the Bluetooth disconnection issue!

I added a dedicated 4.5V battery for the ESP32 instead of using the 5V from the L298N motor driver.
Now the car is working perfectly—no more Bluetooth disconnections!

I’m not sure what the original issue was:

• Motor noise being transmitted to the ESP32 through the 5V line, or
• The shared voltage from the six 1.5V batteries dropping too low for both the motors and the ESP32, causing power loss and Bluetooth drops.

But it’s fixed now!
(the esp32 is the esp32-cam version so i will try to add the wifi cam to the car now, )

I got a chance to look up the data sheet today for the motor driver, and it was basically that.

From what I read the 5v output (the L298N uses a 78M05 regulator for 5V) will completely cut out due to the voltage sagging when the batteries are under load as the minimum voltage it can run on is 7volts. The 78M05 also has a max output limit of 500ma's. From what I could find the esp32 cam when using BT, and WiFi pulls about that much. The 78M05 was probably getting very hot if not close to burning out so it is probably a good thing it was shutting down like it was as if it didn't it would have probably burnt up the regulator eventually.

Also something minor that battery you plugged into the ESP 32 will probably cause issues when it discharges a little as the ESP32's min voltage is 4.4v. But if you keep it topped up it would probably last as long as the batteries in the vehicle.

BTW there is another reason I looked into this, and that is because I have 2 project ideas for ESP 32 cams that I have been thinking about implementing which could have ran into a similar situation you did