Green pre troubleshooting

[peterc]

For testing, you can use 2N3904's, they are the same pinout as BC550 but not particularly low noise parts.

Peter

 

[dustartist]

I used a couple of the NTE 123AP for Q1 and 2 until the BC550's arrive, and the pin voltages before IC's inserted seems normal now.

 

[dustartist]

Got the voltages right, the CMRR dialed in, all the parts back on the board and........back to square one. Still hissing on - side. :sad: :sad: :sad: :sad:

 

[dustartist]

All of the voltages are correct with IC's inserted, EXCEPT IC2 Pin 7. Where I should have 0V I have .89v, which has got to be my noise. Where could this be coming from? I have tried different 5532s with the same result.

OK. 3 consecutive 5532's from the same batch were bad. No wonder I couldn't find the problem. The new ones I bought with different #'s on them are fine. That was a long and arduous hassle-a-thon. I guess the zeners that failed destroyed the first IC, but that was IC1. The problem showed up in IC2. The zeners probably failed because I had the transistor oriented the wrong way. That still doesn't explain IC2, except maybe I got a hold of a bad batch. I hope that it works after I close the box. thanks for tolerating my "research". :guinness: :guinness: :guinness: :guinness: :guinness: :guinness:

 

[matta]

Hey Man!

Glad to hear you are all up and running. It has been a long road but you can now sit back and enjoy your pres! I am still loving mine and thinking of building more.

Cheers

Matt

 

[3nity]

never mind.

 

[Hammond]

Are the CTBC550C the same as BC550?

 

[3nity]

For testing, you can use 2N3904's, they are the same pinout as BC550 but not particularly low noise parts.

Peter

figure if they share pinout!!

 

[sam system-d]

Hello to everyone,
First of all, I would like to thank everyone from this forum for their great work.
I started diy stuff one year ago, with simple guitar gear.
I'm a sound technician, so I moove to studio gear.
My first try is a green preamp, 4 channels.
I've just got a problem on it, and I was searching on the web, apparently no one had this before.
I've read that 3 caps need to be 63v, others can be less.
My power supply delivers +14.8v/-15.2v.
On all channel, the "green" 10R resistor burn everytime.
On all channel, the second "green" 47u caps blow up the frst time I powered the unit.
On all channel, the first "green" 47u cap seems to be not fine...
They are elna 47uF 25v.

I will replace all caps with higher voltage, but if anyone has an idea on this, I'd be happy to know it.

have a nice day!

 

[peterc]

I cant see the pic, but if the caps are blowing up, then there is a dead short somewhere.

Did you follow the setup docs & test the voltage with the ICs removed?

 

[sam system-d]

Thank you Peter for replying!
This is my next move, but I'm surprised that it happened on the 4 channels.
I took the V14 pdf, and etched the board myself.
here is the link for the picture
http://img97.imageshack.us/img97/7235/v14all.gif

 

[peterc]

Sorry, still cant see the image, but try testing for shorts between the power rails, after the 47uf caps etc.

Peter

 

[sam system-d]

So I finally had time to do this...
Newbie mistake...
As on every board, the same thing blow up/burn everytime, I thought I f#*k up my mods (putting 48v, phase, led meter & hpf on a separate board). I was right.
4 NE5532 dead, few resistors, few capacitors...

Conclusion :
YES SAM, DOUBLE CHECKED IS NEEDED!  ;D
Thanks to every one, this forum is just awesome, I'll post pics around here (where exactly in the forum?) of my 4 channel Green mic pre, and soon, my Gyraf G IX...

 

[peterc]

Well done, good to be able to  find mistakes like that and learn from them.

Post pics in a new tread.

Peter