OK, how bad did I screw up?

[Reggie]

Hey good people,
I really need to not build these things late at night. Did a couple dumb things. On one of my A12s, I managed to put one of the 1K trim pots where the 10K should be and vice versa. I didn't find this out until after I powered it up and checked voltages and moved on to my next A12. I seem to be getting the correct voltages, so maybe I am OK having the pots reversed?

The other dumb thing I did was not putting down the grey paper for the transformer like Nerdy did. I knew what to do with it and it was staring me in the face, but in my late night stupor I threw the thing in without it. Did you have any problems with this Nerdy? Anyone?

Other dumb stuff I did but fixed: soldered the ceramic caps in the wrong spots; busted one of the XLR jacks clamping it to run the tapping screws through; dam near got one of the tapping screws stuck in the hole. Miracle of God if these things actually work and sound good when I get done with them.
Maybe by the time I do a few dozen of these (if orders start going out again) I will finally get good at it. My second build has gone a lot faster.

Edit: Oh, and that light on the PCB doesn't light up on the card with the misplaced pots.

[Reggie]

Well, I went ahead and powered her up and......SUCCESS! Despite my attempts to screw them up, both channels work and sound as near to identical as I can tell. Phantom even works. Sounds very crisp and as they say, fast. Can't wait to try some drums through them, but I think Vox are coming up first. Next: J99's!

BTW: I would still like to know if any of those screwups are going to mess something up. And it would be nice to get that pretty red light to go on.

[Category 5]

The red ligh is a diode and will only light when installed according to the correct polarity. Perhaps you instaleld it backwards.

You should order new pots and put the correct parts where they belong. The pots are for setting the +/- voltage and trimming the DC offset. If the DC offset is too high the preamp will clip prematurely (which may or may not affect you in your particular usage).

Be careful removing the pots, and just don't try to save the part. The board is what's valuable, particularly after it's been stuffed! I have found it easiest to use solder wick to remove solder (use the very tip and clip the used part each time for effectiveness). If you can get at the pins of the components clip them and remove them with tweezers one at a time, then clean the holes with wick or a solder sucker.

Good luck! Next time only build when you are alert. Careless mistakes are often the most costly!

Shane

[Reggie]

The light looks like it is in the right way. Maybe just a burn out? I guess I will try to replace the pots, but I'd REALLY rather not due to the risk that I might screw other things up while I try to remove them. Anyone have a second opinion on this?
What is the difference between a 10K pot and a 1K pot (9K, duh) anyway? I mean, is it just a matter of having a wider range of adjustability, or will having the wrong one in there mess up the voltage when things like gain or phantom are applied? I honestly was getting the right voltages as is, although I didn't test the voltage as I messed with gain and stuff.

[Sean Halley]

Unless I'm wack, the LED on the A12 is not supposed to light up. Its purpose it to provide a stable voltage reference for other parts of the circuit (offset correction - from the A12 assembly docs).


S..

[Randyman...]

My LED's certainly light up on both of my A12's. Odd...

[Sean Halley]

Do they light up at idle, or only when signal is passing through the circuit? I've never looked when actually passing signal through it....

Just to make sure, I'm talking about the LED at D1....


S..

[Randyman...]

Mine light up as soon as I apply power, and they stay on IIRC. If you are not seeing any light from the LED, I would assume something is amiss. I'm still a DIY Noob . 2x J99's on the way, too!

[Sean Halley]

Interesting. They biased and setup WELL within spec, as per the assembly instructions. Other than being a tad bright (I'll be doing the ol' 1200 ohm mod here soon), they work as they should....

Beezarre.



S..

[Reggie]

Yeah, something I did made one of my A12's have a working LED (the one with the paperless-bottomed transformer), and the other one without the LED lighting up (the one with the trim pots in the wrong places). But they both sound pretty great! Ordering my J99's right. .... now.
Hopefully the wait won't be too crazy on them.

[Category 5]

LED's are diodes. They are polarized and will not light if installed backwards.

[Reggie]

LED's are diodes. They are polarized and will not light if installed backwards.

Or if you install them the right way, but install other parts incorrectly.

[Reggie]

Ordering my J99's right. .... now.
Hopefully the wait won't be too crazy on them.

Well crap, they're on there way already! Sorry I doubted you Tim!

[nerve346]

How does that idea sound to you? |)

[Reggie]

Sounds great!!??



How 'bout banning this troll-boy? I'm not interested in online casinos.