A12 Assembled, but no sound...

[Todzilla]

Passed the blatant short test, a little unsure about how to perform the tests in step 33, as I have the wiring harness. Not sure what is meant by "Connect the PS03 to J3" and with power supplies, i'd rather not guess.

Didn't smell anything scary, LED lit up fine.

I triple checked my work to make sure everything was in its right place and polarities were carefully observed.

Tim, or someone else, can you clarify how to do the power testing of step 33 with a wiring harness?

Also, I'm afraid I trashed a 470pF cap and had to borrow one from my second A12, which I'm not going to work on until I hash this first unit out. Should I order another cap from digi-key directly?

Thanks in Advance...

[tpryan]

Have you installed jumpers or load isolators at L1 and L2?

[Todzilla]

Yes, those zero ohm resisters with a single black band at both L1 and L2.

[tpryan]

Voltages measure fine and the op-amp is installed?

[Todzilla]

Voltages measure fine and the op-amp is installed?

That's my next step, but the instructions seem to have been written pre-wiring harness, so I'm a little hesitant to poke around speculatively.

Op-amp is installed, but does it need to be for voltage readings?

[Todzilla]

Voltages measure fine and the op-amp is installed?

Voltages measure as follows:

U1 Pin 3 to Pin 4: +14.1
U1 Pin 4 to Pin 3: -14.1

That should indicate I'm good, right?

Let me try a couple other things. I have tomorrow off from work and spouse and kid have work and school respectively, so I can devote some time...

[Todzilla]

Update: When I retest the voltages at U1, my DMM fluctuates. Sometimes it reads "0," other times it goes to +14 and -14. Should I suspect some problems with a solder joint?

[tpryan]

Read steps 33 through 35 again. Test your meter on a 9V battery. If you can't get the voltages right at the op-amp pins, there's no point in going further.

[Todzilla]

Tim, first off, let me apologize for being such a dimwit regarding basic electronics.

I think I didn't fully comprehend how to use my DMM. I think I figured it out and now my voltages consistently measure:

U1 Pin 4 to Pin 3 = +14.2
U1 Pin 4 to Pin 5 = -14.1

I take this as an encouraging sign. Now, I've adjusted R25, R29 and R16 to the desired voltages.

I'm ready to try again in the studio, but I noticed the Op Amp is very loose and falls out of its sockets readily. Any tips? Should I solder one leg in, just for security?

I think I'm very close and don't want to stumble at the finish line.

[tpryan]

I'm ready to try again in the studio, but I noticed the Op Amp is very loose and falls out of its sockets readily. Any tips?

Push it in firmly. You should be able to invert the board, shake it, and not have the op-amp come out.

Should I solder one leg in, just for security?

No. If the sockets won't hold the op-amp, something's wrong.

[Todzilla]

Will do with the Op Amps tonight.

FYI, I did solder in the MillMax receptacles, but thusfar, I've been afraid of pushing the Op Amp in too forcefully.

[tpryan]

I hope you don't mean you got solder inside the sockets. That would definitely keep the op-amp from seating properly.

[Todzilla]

I hope you don't mean you got solder inside the sockets. That would definitely keep the op-amp from seating properly.

No worries, I meant I soldered the Mil Max connectors into the board as directed.

Update: I did get the Opamp in. I took a little harder push than I originally wanted to push, but it snugged right in with a slightly harder than gentle push.

I verified all the voltages and adjusted those variable resistors (R25, R29, R16) to spec as indicated in steps 34 and 35. Everything checks out, but...

When I fire it up, plug in a mic and put the output into my MOTU converter, I get nothing. if I jack both gain and trim to max, i can hear a little hiss, as one would expect, but it won't pass signal for either a dynamic mic or a LDC mic with phantom power.

Tim, any suggestions? I'd rather not send it back if your policy is to just send me a refurbished unit for the assembly difference. I'm not faulting your policy, but I really would prefer to know where I failed (especially since I'm otherwise ready to start the second A12). It would appear to be a relatively trivial failure, since everything measures up.

I have a local electronics guy who could probably troubleshoot it for me with schematics and assembly instrux.

Any suggestions?

[tpryan]

Can you post a few photos?

[Todzilla]

Thanks Tim!

Here's the front

Here's the back

I am hopeful these are hi-res enough for you to see my handiwork and identify if there's a minor problem somewhere.

Cheers,

-Todzilla