Downboy doesn't work

[tylerdurden]

Downboy doesn\'t work

I just built a Lux-III/Downboy700 McLux head for 2x123. Before I potted it in the head, I tested it and it worked fine - just the emitter clipped to the lead wires, the ground wire from the downboy soldered to the ecan, and the board epoxied in the bottom of the ecan. I then potted everything with AA like usual, let it cure in the toaster oven for 10 minutes, soldered the leads to the emitter, and then tried to power it up. Nothing, not even a flicker. How do I troubleshoot this without disassembling everything?

I have a cheap multimeter, but I have no idea how to use it. Is there something I can measure at the emitter to see what's going on?

 

[dat2zip]

Re: Downboy doesn\'t work

The LED isn't backwards is it?

You can use the ohmeter function on the DMM and measure between the ecan anode pad to the LED +. It should be near zero ohms.

You can use a single 123 to hook directly to the LED to see if it lites.

Bummer on your mod. Hope you can fix it.

Wayne

 

[Chief_Wiggum]

Re: Downboy doesn\'t work

You can also use the DMM to check the ground. Check the ground pin on the DB with the side of the McLux head. Should also be 0 or very near it.

 

[tylerdurden]

Re: Downboy doesn\'t work

The emitter is installed correctly.

Wiggum, you may be on to something. I touched one probe to the GND hole and one to the side of the ecan, and I get 20 ohms (not sure if I need to multiply that by some fraction or not). When I touch the probes to the GND hole and the head itself, I get nothing. Also, when I touch the probes to the ecan and the head, I get nothing. I'm guessing this means the ecan isn't in sufficient electrical contact with the head?

I then went back and tried Wayne's suggestion. Touching the probes to the Vin+ pad and the LED anode hole on the board produced the same "20" ohm reading. Probes on the Vin+ pad and the LED+ lead gave me nothing. Maybe I broke the conductor in the lead wire?

I have a 2xAA battery holder with loose lead wires, is it safe to try to directly power the emitter while it's connected to the converter or do I need to desolder?

Thanks for the hints.

 

[dat2zip]

Re: Downboy doesn\'t work

Let's see. As I recall, I goofed my first ecan and only had the LED wires after potting... DOH...

I was able to fix this by adding a small wire on the bottom of the converter board from the GND hole to the ecan. This would fix the GND problem.

Still, the battery anode to LED+ should measure continuity. That worries me.

You can safely test the LED in place with the 2AA adaptor.

 

[tylerdurden]

Re: Downboy doesn\'t work

The emitter does work. I haven't totally killed this thing yet!

I'm confused. If I read continuity between the Vin+ pad and the GND hole on the bottom of the board, I should be able to measure continuity between the Vin+ pad and the emitter + pad, shouldn't I? There must be a short somewhere, but I can't think of how it could have happened. /ubbthreads/images/graemlins/thinking.gif

Something tells me I'll be giving this thing the old acetone bath tomorrow.

 

[dat2zip]

Re: Downboy doesn\'t work

What?

Continuity between the battery anode pad, and GND?

I think I can explain this. The edge of the board might be touching the side of the can. The copper for GND and other components go right to the edge of the board including Vin.

This is really my mistake and I appologize for this. The bare copper at the edge should be de-burred with a dremel or sharp exacto knife and carefully inspected for any exposed copper on the edge. Otherwise, coat the edge of the board first with nail polish or something to ensure the bare edge won't make contact with the inside of the ecan.

Depending on how you glued the board to the ecan you can move the board. Try heating the board to 140F or so, then see if you can move the board laterally one direction or another. It won't take much and once you clear the short the module might start working.

Wayne

 

[tylerdurden]

Re: Downboy doesn\'t work

OK I will try that tonight. Luckily I only used a relatively small amount of AA when potting this module.

 

[tylerdurden]

Re: Downboy doesn\'t work

Hrm... OK... I got the ecan and downboy out. It works fine now that it's removed from the head! The downboy is still potted in the Ecan. WTF?? I'm now just touching an emitter to the lead wires and then touching a 2xAA or 4xAA battery holder to the Vin+ pad and side of the ecan. It lights up in direct drive or regulated mode as expected depending on input voltage.

 

[tylerdurden]

Re: Downboy doesn\'t work

OK, I think I'm got it. It appears that when the ecan is in the head the ecan and head aren't making good electrical contact. there was a bit too much AA on the rim of the can. I scraped the AA off with an xacto knife, filed the edge a bit to make sure the metal was exposed, and re-epoxied the can in the head, this time putting the glue on the inside wall of the cylinder of the head instead of on the rim and the bulkhead of the head. Resolderd the leads to the emitter, and we're in a go mode.

Thanks for the help.

 

[dat2zip]

Re: Downboy doesn\'t work

Interesting. Don't know what to say...

It sounds like it is working now. Why? How? I can't offer any additional input.

Maybe the board has shifted during the removal process and the short is gone.

If that is true, it could go intermittent and come back at some later time.

Wayne

 

[tylerdurden]

Re: Downboy doesn\'t work

/ubbthreads/images/graemlins/icon3.gif /ubbthreads/images/graemlins/thinking.gif

I think it will be OK. with the amount of AA inside the can, I can't see that this thing shifted. I'm pretty sure there just wasnt a good ground path between the can and the head. We'll see.

 

[McGizmo]

Re: Downboy doesn\'t work

Tyler,

I'm getting into this late so I am probably missing something simple but if the E-can is grounded, the head needn't be grounded anyway??!?! With the anodized heads, the electrical isolation makes it easy to bond the LED to the heat sink with no concern that it will be in electrical contact with the head when a DownBoy is used.

The ground path *should* be from the battery tube lip through the shoulder of the E-can. /ubbthreads/images/graemlins/icon3.gif