[BUILD] Hairball Audio "Lola" Mic Pre - On Sale Now

[ebremot]

I suspect one of my DI JFETs is bad - it seems only the positive half of the waveform is getting though when playing a guitar straight in - also giving a slightly ring modulated sound. Is there a good way to test whether one (and which one) has failed with test oscillator and a scope?

Otherwise everything works and sounds great...

 

[Echo North]

Check your signal at the source.  Probably just your Q3 is bad, they are not a push-pull set up.

You can fill out a missing parts form for a new set if you like.

 

[Echo North]

Hi Mike,
Please see attached photo. I did check all those things. Any thoughts? could it be the main board? any other thoughts?

Not the main board. Probably a damaged semi conductor and the soldering looks a little suspect (hard to see for sure). Make sure you LEDs are in the correct orientation, especially the ones not lighting.  You could replace the semi's. Or just send it in for repair.

 

[Carl Cress]

Hi Mike, Yes I hit them with an extra touch of solder when I was refloating them so a little more solder than I would use. In the photo you can see that the LEDs are configured correctly. I suspect one of the chips but have no way to test them except that I tested continuity from the bottom pad to the top of the legs and every joint is good. If I decide to send them to you what's the turn around?

 

[Echo North]

Usually 2 weeks. You can just send the meter and you can use the pre without a meter.

 

[ebremot]

Check your signal at the source.  Probably just your Q3 is bad, they are not a push-pull set up.

You can fill out a missing parts form for a new set if you like.

thanks - i just filled out the form for a new JFET. my signal looks good on the gate of Q3, but not at the output (forgot if that's source or drain).

 

[Echo North]

thanks - i just filled out the form for a new JFET. my signal looks good on the gate of Q3, but not at the output (forgot if that's source or drain).

Curious what your DC V is at each the source and drain?

 

[ebremot]

Curious what your DC V is at each the source and drain?

drain is about 16v, source is about 2.5v with the positive half of the signal on it.

 

[Echo North]

drain is about 16v, source is about 2.5v with the positive half of the signal on it.

Hmmm I'd have to check mine, but we'll get the new parts out.

 

[Carl Cress]

Usually 2 weeks. You can just send the meter and you can use the pre without a meter.

Could the fact that all the R114 are .723k instead of 723R in the LED meter bags have something to do with my meter issue?

 

[Echo North]

Could the fact that all the R114 are .723k instead of 723R in the LED meter bags have something to do with my meter issue?

That is the same reading. .723K=723Ω.

Be careful reading resistors in circuit, you can get complex/unexpected readings if they are in parallel with other components. Though that is not the case above.

Mike

 

[Carl Cress]

Had a duh moment. Grasping at straws. The second meter works fine? If I can't sort it out tonight I will overnight to you tomorrow...

 

[Echo North]

Had a duh moment. Grasping at straws. The second meter works fine? If I can't sort it out tonight I will overnight to you tomorrow...

Make sure you email us for a repair number.

http://www.hairballaudio.com/build-support-services

 

[Carl Cress]

I'm shipping tomorrow. Can you give me the ticket # now? If not the request is in your mail.

 

[Carl Cress]

Hi Mike,
Time is of the essense. I was wondering if I could just buy the Meter PCB kit box you pack with the Lola and have it shipped?

 

[Wazatron]

Hello all - this is a follow up from my initial post in Reply #255, as well as the follow up in Reply #256. I was out of town for a bit and have just been able to get back to troubleshooting. Quick refresher to hopefully avoid looking back, the root of my issue was:

So when you power on, the relay switch is either A) not getting power to it or B) the relay is damaged.
Start by making sure every leg on the relay is solder correctly.

I've been able to check soldering, and I've also gone ahead and re-flowed all the joins on all relays, just in case, but specifically looking at K4 as the switch to change the input from the XLR into the 1/4” DI jack.

I've had no luck at all, unfortunately. I'm attaching an image of the underside of my board to view the solder joints of the this relay, as well as the other two next to it. Any thoughts are appreciated!

Not sure why the image doesn't display inline, I'll have to read up on that. But if you right-click on the broken image and open-in-new-tab it should open okay.

 

[ebremot]

thanks - i just filled out the form for a new JFET. my signal looks good on the gate of Q3, but not at the output (forgot if that's source or drain).

The new JFET fixed it nicely - thanks! I just went ahead and built my second as well, everything clear, clean and quiet.

I'll be trying out this pair of Lolas in a couple recordings next week - and as soon as budget permits - I believe a pair of Elements Copper are in my future...

 

[Wazatron]

Sorry to be a bother, but I wanted to check again on my issue in « Reply #275 on: May 10, 2017, 12:50:58 AM ». It's been just over a week since I posted, and I'm anxious to get this Lola up and running. Thanks!

 

[TillM]

Hi Mike,
just want to thank you for the fast shipping and that you attched the bill outside. This makes the customs process really fast.

Build was very easy, took me 4 hours and the Lola runs up. I enjoyed it on all sources I test it.

@Wazatron
I can't see any picture, please post again.

 

[Wazatron]

@Wazatron
I can't see any picture, please post again.

Not a problem - attached is the image of the solder joints for the relays (at this location). I'm happy to provide any other pictures that could help as well.