Help Adjusting Dave's Dual Drivers

[tribble]

Are the grounds from both your mod power supply and drive supply tied together somewhere?

Yes, they are actually the same supply. The modulation voltage is obtained through a voltage divider network with a pot to vary it between 0 and 5V.

[tribble]

Yep. Have you linked Dave up to the thread? He was great when I did my best to kill a couple of mine.

Not directly. I will send him a PM and point him to the thread.

[logsquared]

Strange., Maybe you need a lower value pot?

[tribble]

Have you tried setting your drive current a bit higher? 140 seems very low even for testing

150mA is the maximum recommended current for that diode per the spec sheet I have... 200 is the DTR suggested max.

[tribble]

Strange., Maybe you need a lower value pot?

Dunno... 5v is 5v, right? There is no appreciable draw or drop through the pot.

[norty303]

Sorry, was assuming you were using a multi mode 445/462/637/520 diode which needs higher current.

[logsquared]

Dunno... 5v is 5v, right? There is no appreciable draw or drop through the pot.

Yeah, if you are measuring voltage at the wiper with it connected to the driver. I mentioned it because i built a rgb pot box with 1k pots and with the input impedance of most drivers it takes a 1/5 to 1/4 of a turn or so to hit a 1/4 volt. So, a 5k or 10k would be really bad. Not sure what the Zin on daves are?

[tribble]

I got a PM back from Dave. In summary, Dave says that all drivers are tested before shipping and asks if I've tried using 5v straight out of the PSU (yes) and have I tried actually using laser software (no). I have Beyond and an FB3 here but figured I would dry-fit some things on the bench and see how they worked before cutting metal. Apparently that is not a supported use case... I suppose I will wait until I obtain the rest of my parts and get the projector actually built and see how things work and give up on the bench testing.

If it works when everything is assembled, great! If not, I guess I will ship it back to Dave and see if it works for him.

Best,
Mike

[tribble]

Yeah, if you are measuring voltage at the wiper with it connected to the driver. I mentioned it because i built a rgb pot box with 1k pots and with the input impedance of most drivers it takes a 1/5 to 1/4 of a turn or so to hit a 1/4 volt. So, a 5k or 10k would be really bad. Not sure what the Zin on daves are?

Interesting. Yes, in any case, modulation voltage was measured across the modulation input pin wires.

[tribble]

OK! I think the final diagnosis is in, and here are the results: tribble is a dope!

Per a question Dave asked in a PM, I hooked up the other side of the driver board (channel 1 vs. channel 2) and it worked like a champ! No standby lockout weirdness.

I have a second board and I have not tested it to see if it has the same behavior, but for the moment I am just assuming that I somehow cooked channel 2 when soldering the pin headers on to the board. Either that or the board doesn't like to have just one channel hooked up, but my money is currently on me messing it up somehow.

SO! I apologize for the whole business, but I sure was puzzled... usually when I cook something it doesn't work at ALL, none of this "kind half works when the moon is 3/4 phase" business. :-)

Thanks again for all the support. I'll get there eventually, by golly.