anyone know anything about this cheap 8 channel mic pre?

[SonsOfThunder]

Yep, okay, be sure when you check those wires that you are set on AC volts! Blues and black will be the +/- 15V, the whites are for the phantom.

HTH!

 

[wiz1der]

Hope this is right, but it appears to be the transformers. I have 120v going in via the red and black wires, but i do NOT have 15v at the blue and black. Same for the phantom, 120v in, and 0v at the 2 white wires.

Also, a simple comtinuity check of the transformer with no power should give me a beep when connecting both sides right? say either red or black to blue or black on the other side right? Sorry if this is a dumb newb question.... there is no continuity through neither transfrmer.

My next question is, what could cause both of these transformers to go out? Is there more components blown out as well? And if I wanted to head down to an electronics store for transformers, what would I ask for?

I do have to say that it feels good to be making headway on this thanks to your guidance. I feel that I WILL get to the bottom of this, and it will give me confidence to start my other projects!! I guess everything happens for a reason after all!!

 

[SonsOfThunder]

I find it very strange that both trafos are dead. Are you sure you measured AC volts?

I can check the o/p voltage and or ask SM Pro about the spec for the trafos. Just guessing that the bipolar supply trafo is maybe 25-0-25, and the other is probably ~ 75V.

HTH!
Charlie

 

[wiz1der]

[quote author="SonsOfThunder"]I find it very strange that both trafos are dead. Are you sure you measured AC volts?

I
HTH!
Charlie[/quote]

what I did was just a simple continuity check. (the beeping signal?), to see if the out was connected to the in on the trafo. I got no beep at all, This would indicate a broken winding inside correct?

If I would replae one trafo just to try it out, It would be the main 15v one as I do not really need phantom on this unit.

 

[pmroz]

what I did was just a simple continuity check. (the beeping signal?), to see if the out was connected to the in on the trafo. I got no beep at all, This would indicate a broken winding inside correct?

Hi, i'm a newb also, but ... don't know if you should get 'continuity' through the trafo. primary and secondary windings are separate, so if you're checking in to out... hmm...

someone that really knows should jump in...

 

[SonsOfThunder]

As i understood wiz1der, he was calling out wire colors on the secondary side of the trafo. I have the unit he is talking about so I thought I udnerstood.

I think he meant to say continuity from either secondary lead to the center tap lead. That's the reason I was trying to get verification that he was measuring AC volts on the o/p. But perhaps i am assuming too much.

I have 120v going in via the red and black wires, but i do NOT have 15v at the blue and black. Same for the phantom, 120v in, and 0v at the 2 white wires.

If the measurement is with the meter in "AC volts", this would indicate bad trafos to me. If the measurement is with the meter in "DC volts", this is the expected result! I hope I was clear about that in my previous post.

:green:

Peace!

 

[pmroz]

yes sons of thunder, you're helping more than i ever could... i just noticed wiz1der's full post above: he quotes your ac question, then replies:

SonsOfThunder wrote:
I find it very strange that both trafos are dead. Are you sure you measured AC volts?
I
HTH!
Charlie

what I did was just a simple continuity check. (the beeping signal?), to see if the out was connected to the in on the trafo. I got no beep at all, This would indicate a broken winding inside correct?

...so just thought.... well you know....

 

[wiz1der]

WHEWWWW!!!!

Thanks for hangin in there guys! Even a new guy trying to jump in and help! i LOVE THIS PLACE!

Anyway, After reading you guys' responses, I didn't want to give up so I went back to the unit and really started seperating wires, following them and there were a couple brittle connections, I gues from transit? I hooked them back up, and IT WORKS!!

:sam:

now ON WITH THE UPGRADES!!

First of all i want to remove C13/14/15, and replace with jumpers, as was discussed earlier. I will do that on 1 channel to see (hear) th difference.

Being new, I see them in the schematic, but I am not confident enough to just get started, so maybe someone can help me identify these parts?

My best guess is:

http://groupdiy.twin-x.com/displayimage.php?pid=115&fullsize=1



Can someone confirm? I will also go purchase 16 sockets to prepare for my OPA 2134's

 

[SonsOfThunder]

Wiz,

Could we move this discussion back to here:

http://www.groupdiy.com/index.php?topic=344&highlight=pr8

Your pic is much better than the ones I took a while back. They were so bad I didn't want to post them. Can you take a pic of the o/p board too and I'll upload them at work and put locators on the whole thing. :thumb:

Thanks!
Charlie