Windell -

OK. Eight panels soldered in my spare moments, and the infant death LEDs culled...

Now, however, I have two boards where some LEDs remain lit, to wit:

Board the First: two sections, each showing four of the five LEDs lit. One section is fairly bright, the other quite a bit dimmer. No obvious solder bridges or cold joints under magnification.

Board the Second: one section, four LEDs in one section, fairly dim.

All of the sections in question appear to function correctly otherwise.

I've managed to securely file the manual so I don't have the circuit diagram to mumble at, so any guidance is welcomed!

Oh: version 4.1

Thanks!

Kevin

So the LEDs are arranged in sets of 5, in overlapped 'M' or 'W' shapes. When four of those LEDs are too bright or too dim, the fifth LED in that set generally needs to be replaced.

Got the "W"/"M", and identifying outliers. Should I replace the LED in each set that *doesn't* remain lit?

Yes, that's correct-- if one remains dark while the others are lit, it's the one dark one that's the problem.

OK, before I get the solder sucker out again, I want to be sure: all five of the LEDs in each set light up on cue - and at what looks like the same brightness. One in each set, however, goes dark at rest while it's partners remain a bit lit. So, replace the one that's "behaving"?

Just want to be sure, and not subject the boards to unnecessary trauma.

Yes, that's correct. Even says so in the assembly manual.

(And, to be clear, it's not behaving. If you have five LEDs in series, and put current through them-- that is, the same current through each LED --they should all light up equally. Every once in a while, either by construction or soldering, one changes enough that it no longer lights up when the others do. Its current/voltage curve has been skewed enough that at this constant current, it draws less voltage than it should, leaving too much voltage across the other LEDs, so they light up.)

OK.... pulled, cleared. and replaced.

One section still remain lit, but at markedly reduced levels. I hadn't noticed before, but is it normal for a few sections to remain barely lit? Just a hair over the forward voltage applied? (I haven't checked the voltage levels, but it's got to be just over 3.6 volts/led for white, right?).

Too used to digital.

I'm afraid that it may be normal. There is typically some variation. One thing to check for: in both the overlaid M and W (including the one that stays lit), check to see if one of those LEDs-- any of them --is a little bit out of balance-- a bit dimmer, or one that goes out sooner than the others. If so, you may be able to fine tune it a bit further. However, when it's down to "markedly reduced levels," we usually leave well enough alone.

Windell -

Thought I was done!

Had three panels cooking overnight - my two problem ones and the 'power supply'. This morning two are working normally, but the middle one barely lights. It functions, but very dimly. This is all four quads, all sections.

Thoughts?

Thanks -


Kevin

That's odd. Operation is fully normal, but the maximum brightness is lower, or is it the case that it's less sensitive?

Try turning the power off and back on. When it comes back on, is the middle panel less bright in the initial transient, or is the same brightness?

Max brightness *far* lower, but fully functional. Power recycle has no effect.

Is there a single path from the power bus to the electronics? If so, perhaps a defective component that would hit te whole board?

Power recycle has no effect

Say what? The LEDs should flash on, very intensely, when you first apply power-- are you really not seeing this? Or are you actually seeing it, but it's dimmer than the other boards when it does that?

Is there a single path from the power bus to the electronics? If so, perhaps a defective component that would hit te whole board?

Maybe one that is relevant, but it's a little hard to buy. There are actually a lot of taps to the edge power busses (that apparently power the other two boards correctly). The one place that could, perhaps cause a problem like this would be D1 and D2, but it would be surprising if they both went, *unless* there's a short circuit somewhere on the board-- so check carefully for any stray bits of metal or solder bridges.

If you have a multimeter, measure the voltage across D1 and D2, as well as the voltage across one of the op amps-- measure between pins 7 and 11 (the middle pin on each side).

Also, any effect different running with or without the extra two boards attached?

When misbehaving, no bright flash.

Note the "when"? After leaving it off for maybe 6 hours, it behaved for five minutes, then dimmed. Then awhile later, good. Then not.

I can't predict or force it; sometimes it seems fully bright (not often), often mid-bright, the rest of the time dim. Often, the photo transistors seem less responsive - but again, that condition varies...

Sigh.

Voltages: diodes, .6 -.7, op amps 22.8 or ---- wait. Zero. The power supply just died! Input good, output in the mv range! No pops, snaps, or crackles. No magic smoke escaping.

Unplugging it for awhile seems to help - in that it functions again. Right now, I don't trust the supply - even though it is powering five boards without problem, including the funky one.

Oh - the supply died while powering only the original board. I haven't found any bridges or other shorts that coulda stressed the supply, so it seems to be just bad luck. Acted like a hot reset, though... maybe I shorted something while measuring, even using needle probes? Darn.

I'll let it cook overnight again and see what happens.

Question: plugging in some boards that have been sitting for a couple months, I see a few more LEDs I want to replace. As the original parts bag is nearing empty, can I buy some more clear white 5mm LEDs suitable for the boards?

Thanks for the support!

If the power supply cuts out, that's also a *very* likely sign that there's a short circuit somewhere-- if too much current is drawn, it should shut itself down automatically. Try using the multimeter to see if you can detect a short somewhere on the board.

Question: plugging in some boards that have been sitting for a couple months, I see a few more LEDs I want to replace. As the original parts bag is nearing empty, can I buy some more clear white 5mm LEDs suitable for the boards?

Yes, I believe so-- please contact our store directly.