SG3524 Help

[nwolfman79]

I am trying to repair a motor control board for one of my machines. It has 24vac input and should put out 24vdc for the motor. I have traced everything back to a chip with SG3524 on it. I have measured the following voltages.
1 - 0.63vdc
2 - 10mvdc at idle / 20mvdc when I press the "go" switch
3 - 92.2mvdc
4 - 7.1mvdc
5, 10, 11, 14
6 - 3.7vdc
7 - 2.2vdc (When I ground this pin everything works, but don't know why)
8 - GND
9 - 12.6mvdc
12 &13 (connected together) - 13vdc (when this output goes low from putting pin 7 to ground the machine turns on)
15 - 13vdc
16 - 5vdc

Can someone help me figure out where to troubleshoot next? Or tell me what I should be seeing for pins 12 & 13 to go low when I press the "go" button.

Thanks for the help in advance..

 

[KrisBlueNZ]

Pin 7 is the oscillator capacitor. I don't know why you tried grounding it, and I don't know why grounding it would make the circuit start working. Perhaps it forces the SG3524 output permanently ON; in that case, the board's output voltage would be more than 24VDC.

I'm assuming it's a non-isolated buck converter, but it's impossible to say much without knowing more about the circuit. Even some photographs of the board would probably help. Take one of the underside at a slight angle (make sure there are no reflections of the light source).

Also it would be helpful if you could trace out the main power path - from the bridge rectifier and filter cap to the switching element (the biggest component on a heatsink) and to the output of the board.

 

[nwolfman79]

I failed to mention the machine is made to run on 230vac or 115vac. The transformer take 230-115 in and puts 24vac to the board. Although I've found when plugged in to 115 the trasformer only puts out 13vac to the board. But it has ran like this for 2 years. The board is a bi-directional 24vdc motor control, it has a speed control, reaction time control and sensitivity control (all variable resistors the operator can control). Here is a link of a demo machine on youtube

. I'm not that familiar with circuits, just like trying to figure things out. So I don't know what a buck converter is. At idle pin 12 & 13 on the SG3524 are at 13vdc when this changes to 0 the motor will run. Those 2 pins run to a HEF4093 on pins 1 & 2, the output from 3 goes to pins 9 & 12 on the same chip, on pins 8, 13 (the other two matching inputs from 9 & 12) are controlled by which direction the operator has the switch. The outputs from these (pins 10, 11) go to a HIP4082 in which the outputs go to transistors. Here are links to the pictures. (It didn't seem like the attaching them was working.

http://s286.beta.photobucket.com/user/nwolfman79/media/imag0520.jpg.html?evt=email_share

http://s286.beta.photobucket.com/user/nwolfman79/media/imag0519.jpg.html?evt=email_share

Thank you so much for the help!!

 

[KrisBlueNZ]

I doubt very much that the unit is designed to run at 115V with 13VAC going to the main board. I've never seen a product that uses a mains-frequency transformer which supports 115VAC and 230VAC without a jumper or switch change on the transformer primary. Have a look for an AC voltage switch connected between the mains connector and the mains transformer.

I need better pictures. Can you take the following pictures:
1. Component-side view of the whole board, viewed from almost directly above (about 10 degrees angle);
2. Component-side close-up view of the relevant section, including the power transistors along the edge, viewed from almost directly above (ditto);
3. Component-side close-up view of the relevant section, including the power transistors along the edge, viewed from about 45 degrees (like imag0520 you posted), but with illumination on the transistors and ICs so I can see their part numbers;
4. Track-side view of the relevant section, viewed from directly above.

For all the views I need clear illumination, but no reflections of the light source. Especially for the track view. Daylight (but not direct sunlight) is best.

It's probably best to put them on photobucket, since they'll probably be bigger than 100k (that's the size limit for forum posts).

Edit: On second thought, it's probably better to email them to me; I've sent you a PM with my email address. I'll post them here for others to view.

 

[nwolfman79]

I sent you an email with all the pictures. Let me know if you haven't gotten them.

 

[KrisBlueNZ]

Thanks, I got them. I'll get back to you.