I think Alec_t and I are pretty much on the same page. I'm probably more of a "suck it and see" person, his testing advice is more professional! You have shown that connecting only one of 7 or 8 works. Maybe connecting them both would work, but there is a risk of damage. His testing with a "temporary resistor (~10k) between the 'grounded' pin and Vcc" makes a lot of sense. Just connecting one of 7 and 8 via a diode will show if the IC output is sufficient to turn the Mosfet on - but it may stay on giving full speed regardless of the PWM mark/space ratio. Try this first?

Looking at the schematic, the red wire should be connected to the 5V output of the 7805, the white wire at the top left to the receiver? Not sure I'm understanding where you are seeing 8.5V.

 

The white wire is the signal (PWM) wire from the receiver telling this device what to do. Seeing 8.5v right at the red wire which powers the receiver.

 

The white wire is the signal (PWM) wire from the receiver telling this device what to do. Seeing 8.5v right at the red wire which powers the receiver.

Sounds like the 7805 is blown. Out of interest, what is the coil resistance of the relays?

 

Do I have this right?

Place a 10k resistor from pin 7 to Vc (5v)?
Place a 1n4148 from pin 8 to ground?
Then I should see one of the outputs running the motor at full speed possibly?

 

Until your recent post I didn't realise you were working with two boards.
DON'T use the board which is giving 8.5V on the red wire. As Sarah says, the 7805 regulator seems faulty. Fix that first. You don't want to smoke the '409 ! Perhaps the instruction about not connecting pin 10 was to allow for checking correct operation of the supply regulator before powering the '409.

Place a 10k resistor from pin 7 to Vc (5v)?

Yes, providing pin7 is still butterflied out. Then monitor the volts on pin 7 when moving the joystick for forward and reverse. The Volts should, I reckon, be 5V for one direction and something less for the other direction.

Place a 1n4148 from pin 8 to ground?

Not if I've understood Jerry's aim of providing a diode-OR arrangement for pins 7 and 8.

 

So what do I do with the diode?

 

I wonder if it would still work in one direction with either 7 or 8 connected via a diode? If the logic level mosfet still turns on with the lower voltage then both 7 and 8 could be connected via diodes

So what do I do with the diode?

If pins 7 and 8 are intended to pull down the R3/R5 junction to turn off Q1, adding a diode there would probably fail to pull the Q1 base down low enough to turn off Q1 (and hence turn Q2 on) reliably. So although I like the diode-OR idea I don't think it will fly.

 

I’m lost again. What to do.

Use only the 10k resistor on pin 7 to 5v and connect pin 8? And see what happens?

Working on replacing the 7805 now.

 

Golden rule. Only ever change one thing at a time. I recommend, leave 7 not connected and connect 8 via a diode to the transistor. I think one of three things will happen
1. It will continue to work in the one direction as before
2. It won’t work in either direction
3. It will work in the one direction but the speed won’t change with changing the input signal
I’m reluctant to suggest the next step until I know the result of that single change

 

I alway use that rule, especially when it comes to electronics.

Replaced the 7805. SUCCESS!!!! Now both are working identically!

You say connect a diode from pin 8 to what?

 

In following Jerry's suggestion the diode cathode goes to pin 8 and the anode goes to the R3/R5 junction.
Good that the 7805 replacement did the job.

 

I do not have many diodes so I used a 1N4001, all I had.

Cathode to pin 8 to anode to R3/R5 junction.
Moving the stick up the motor spins, let’s say clockwise. Move stick down no spinning.

Move the connection to pin 7
Move the stick down the motor spins counterclockwise. Move the stick up no spinning.

 

I do not have many diodes so I used a 1N4001, all I had.

Cathode to pin 8 to anode to R3/R5 junction.
Moving the stick up the motor spins, let’s say clockwise. Move stick down no spinning.

Move the connection to pin 7
Move the stick down the motor spins counterclockwise. Move the stick up no spinning.

Now it should be purely down to whether the relays are switching over, which is controlled by the adjustment of VR1 and its associated components. If you can adjust it such that the relays switch over when you move the stick to the "no spin" side, then try connecting both pins 7 and 8 back up, so that both are connected together.

 

I already have VR1 set so that when the stick is in the neutral center position, the motors are not active. I played with adjusting VR1 to either way to see if it functions correctly, which it does. I also played with VR2 how it controls the motor speed. It is functioning as expected.

Are you saying connect pins 7&8 into the circuit as they appear in the schematics? And without the diode that I inserted?
If that's the case I insert those pins back into the socket and solder pin 8 of the socket as it currently is unsoldered.

 

You have shown that it works with the diode. And you have shown that the reverse works. Now try it with both 7 and 8 connected via a diode.

I’m reluctant to suggest connecting pins 7 and 8 together as I think this is where we started?

 

I think the diode arrangement gives marginal operation, but hey, if it works it works.

Now try it with both 7 and 8 connected via a diode.

For the avoidance of doubt, that means each of pins 7 and 8 is connected via its respective diode to R3/R5.

 

I think the diode arrangement gives marginal operation, but hey, if it works it works.

For the avoidance of doubt, that means each of pins 7 and 8 is connected via its respective diode to R3/R5.

I think we should be getting a PWM signal on both pins 7 and 8, but only on one for each direction, hence they both need to be tied together. If only the TS had a scope!

 

I agree with that, Sarah, but Jerry is playing safe.

 

I agree with that, Sarah, but Jerry is playing safe.

I realise that, and it probably won't hurt, but as the 2 internal NPN's are driven out of phase as part of the bridge circuit, it won't have much effect (I hope!)

 

Unfortunately I do not have a scope.

So pin 7 and pin 8 will each get their own diode and the anodes connected to R3/R5 as Alec said.