Capacitor is messing things up

I think you meant capacitor...not pot..lol. Well I am not so sure a capacitor is even needed with these boards. But yes, you can use it on the input side. If you are using a switch just make sure you put the capacitor in the circuit after the switch. If it is across the batteries before the switch it will always be charged and will not absorb any spikes.

Yep I did mean cap

Why do you say these boards may not need caps? They have only 2 components, the regulator and the diode.

My second board works well with a pot, it is able to have a resistance low enough to dissipate all but about 40ma.

Gazoo, I notice u say that the output voltage should be same as input. This seems to be true but how can this be, I thought the diode on the board was in series?

pocketfluff said:

Yep I did mean cap

Why do you say these boards may not need caps? They have only 2 components, the regulator and the diode.

Click to expand...

Because the regulator should be absorbing any spikes. I feel the same way about the LM317. I don't have a scope to check it out but Daedal did and he did not see any spikes coming out of the 317.

As far as he diode...not sure. I will have to look into that later.

Gazoo, I really think that the source of supply to DX has changed the 7135 chip on the board or a different supplier altogether, which ever , the chip does not work  the same as the older ones. I will try to get a response from DX but don't really expect a solution from them.  Amazing how such a simple solution to driving an open can can present such a perplexing result.
LOL.

 Befuddled is what I have been over this for some time !

Joenobody purchased some boards and got them a week or so ago and I am waiting on his results.

Hmmm...I wonder if they changed the chips on the other DX boards...the ones that use the 7135 but supply up to 700ma's and more. Anyway it's a shame..the 7135 is so reliable when it works.

Gazoo, the #'s on the boards chips that I have are different from what you sent. I am guessing that is why they act differently.

Cat, Gazoo, are you guys able to measure current directly off the board? When I try the board reads nothing, I'm assuming this is some sort of short circuit protection. I'm also assuming that for this same reason my board will not reliably start up if I set the resistance too low across the outputs.

I hate to keep referring to another forum, I know this info originated here but I can't find it and it's bed time for me, but where I sent you before for the thread on these boards has a post on testing the LM317 circuit. Just test the circuit as you would with the 317, what ever feeds the load, the laser diode, is not important but the output to the diode is. You are feeding the diode what it needs to do what you want it to, this thread tells you how to simulate the load that you want to make happy and how to tell if it will like what you are giving it.
I still scratch my head and various other body parts working on these things, thats why I torment Gazoo. C. ;D

Hmm. i think I've got this board nailed now. The cap seems to be ok at the input, it might even be a good thing cuz its hard to zap the diode on the cap since the regulator will sap the caps charge. With the resistor at the output, every board seems to be unique and I need to twiddle it a bit to see what resistance will cause it not to turn on.