anyone have schematic for 1206MX PDS controller?

[Roy Beaty]

Im working on my first cart. The controller 1206MX is bad. I found several bad components and replaced. R66, D4, D5, Q3 and J1(burned pin 5). It still does not work. No voltage out of pin 9, to key switch.
It seems to enter diagnostic mode. I get a long beep after toggling the reverse switch but no beeps follow.
Pedal press causes solenoid to click on and off, about every 1/2 second. No voltage to motor.
Does anyone have a schematic for this controller? I've looked for some time with no luck.
Thanks

[biphase]

Perform this bench test

[JohnnieB]

Here is a drawing showing the various voltage paths through a 1206MX.

The 1206xx family of controller were made exclusively for EZGO and you cannot get a schematic or manual for them from Curtis and EZGO doesn't consider them to be field repairable, so they don't release much of any information about them to the public.

The best thing to do is replace the 1206MX with an Alltrax XCT48400-PDS, user programmable, controller and hold onto your hat. With a stock motor, a PDS cart will do about 24MPH on stock height (18") tires with a 36V battery pack.

[Roy Beaty]

Thanks for the replies.
I fail the bench test step 4 part 2. No connection at all from J1 pin 6 to J1 pin 8. I do have continuity, 0 ohms, from J1 pin 7 to pin 8. I cannot find any other connection on the board to J1 pin 7 or 8. There is no connection from pin7 to J4 pin 2 either. Any advice there?
What components are the "key in"? This is a multi layer board so difficult to follow the traces.
All other tests are good.
I did find a faulty key switch. Very intermittent.
Just to confirm, Battery power comes in thru the reed switch and is series through all the switches all the way to the solenoid and pedal switch?
Thanks again

[biphase]

The banded side of D4 should be connected by traces to both J1-7 and J1-8.
You probably have a burned trace between the banded side of D4 and J1-8.
You should also check continuity between J1-7 and J1-8.

[Roy Beaty]

Thanks Biphase. that is what I needed. I will try an external jumper. Hopefully it will fix it. After buying new Trojan batteries, the wife is asking how much it is gonna cost.

[cgtech]

Ahhh, a bad device is a bad device. Making a new "bridge" usually just fries again, or finds the "next thing up the chain to fry". Add a fuse to your new bridge. And start making plans for a "new one of that device".

[biphase]

Originally Posted by cgtech

Ahhh, a bad device is a bad device. Making a new "bridge" usually just fries again, or finds the "next thing up the chain to fry". Add a fuse to your new bridge. And start making plans for a "new one of that device".

The burned trace was caused by the failure of D4. He has replaced D4 so the failure should not recur. When the solenoid driver transistor fails it is common for D4 to fail as well.

[biphase]

Originally Posted by Roy Beaty

Thanks Biphase. that is what I needed. I will try an external jumper. Hopefully it will fix it. After buying new Trojan batteries, the wife is asking how much it is gonna cost.

Unfortunately there is no way to access the banded side of D4 externally so you will have to find a way to do it internally. D4 is the diode closest to the J1 connector and the banded side must connect to both J1-7 and J1-8. Be sure to run the test procedure again to verify that the connection is correct.
You mentioned that you found no connection between J1-7 and J4-2. There should be a connection there so you should double check that as well. The controller does seem to be responding to the pedal switch so it seems like that connection must be OK.

[Roy Beaty]

Well success!!! Looks like it works now. I installed a jumper from D4 to J1-8. Now have connection to J4-2 also.
Thanks for all the help. Now on to stress testing it :)