Stage Lighting Followspot PCB in need of repair

Hello everyone,

I have two of these unit that were giving problems and I actually managed to troubleshoot and repair one but I am having problems with the other pcb. The units are fairly simple. They run on 12V ~ 18V DC and are powered by a 12V toroidal transformer and have three motors that control a shutter, an iris and a color wheel (the terminals for these motors on on the right of the image). The converter at the top converts the 12V power from the transformer to DC. The pcb I repaired before had a faulty relay and diac (located bottom left) but the other pcb has a different problem. When I power it up, I get 18V at the relay terminals and an audible click from the relay but I am not getting any output. Any ideas? I'll be grateful for any help I can get.

partyanimallighting

 

Here's the thing. My knowledge of electronics repairs is vague. I can check continuity, values, replace burnt out devices but as far as having a working knowledge of how pcb's work, forget about it. That's where I turn to the experts, you guys. So here is my response to your questions....The "normal" unit pulls the relay in when it's powered up and the red LED on the pcb lights up. I checked the relay in this pcb and I am getting an audible click and 18V in but nothing out. It's a new relay so this device should not be the problem. That's about all I can give you for now. If it will help, I'll compare the voltage out on the working pcb and let you know what I get.

 

Do you mean to test both pcb's at the same time? I'm trying that without much success. I have the pcb powered up and checked voltage at all the resistors etc. and I'm getting 18 volts at all solder points. Anything else I can try?

 

it looks like the relay closes to send continuity so I am getting a 0V readout on both. I did this comparison test before and both readouts are identical. Where do I go from here? When I short the legs on the diac or check the values on the three resistors just after the diac, I get a click on the relay. I get fluctuating voltage on these resistors, sometimes around 3V or 8V before, and after the click, 18V but the pcb still does not function. Any ideas?

 

I'll try to post a better photo of both sides as requested and label all connectors. And I really appreciate all the assistance so far.

 

PCB in need of repair

Hi again,

Here is the best I can do as far as picture quality is concerned. I tried to label all devices as best as possible with the exception of the resistors but when the picture is zoomed I think they can be seen clearly enough.

 

How do these look? Will they help?

 

Pix of rear of PCB

Hope these help.