Volume control on a Bauman 312 board?

Well I finally got the power supply to give me the correct voltages so I plugged in the power to the pres. Turned up the gain knob and nothing.

I checked to make sure I was getting power on the boards. I think I may have the output transformer wired wrong.

Any help?

Okay I get no sound on channel 1 but channel 2 gives me a very faint signal. I had to yell into the sm-57 with the gain all the way up to get a signal out.

it's all colour coded - transformer wires to silkscreening on the board...brown and red to unbalanced, grey/purple to VU...uh, and the other wires to the other colours!! green yellow/blue orange...

Edit to add:
Ignore this post. It was late, saturday night, just got home from the bar. Didn't have enough to drink to slur-my-typing but enough to not have a clue.

The wires on the transformer are not the same colors as the ones silkscreened on the board.


http://www.waltzingbear.com/Schematics/API/API_xfmr_pg2.htm

it's the same colors as the 2623 on this page. I was reading somewhere that I had to wire the secondaries in series. I don't know how to do that.

heres the link to that thread...

http://www.groupdiy.com/index.php?topic=18810&highlight=26231

Also check that you have jumpered the 'line in' relay (I just put another relay in there) if you haven't already or if you didn't install one to go with this (line in) option.

Mine didn't pass any signal until I found that out....

I'm passing signal on both channels but the neither of the gain knobs are working. I took an sm-57 and yelled into it and i can see signal on the meters on the computer.

Well that and I got a 1 bad 2520 opamp.

I placed the resistors on the board at RG1 through RG12 in the right order and I ran a wire from each of the 12 points on the gain knob to the place on the board for it. Am I missing something?

I've been looking at the pictures of how everyone else did theres and it looks like most of them soldered the resistors directly to the gain knob then ran three wires from there.

What input transformer are you using? Is it PCB mounted? If you are using a PCB mounted Cinemag and you did not specifically wire the input transformer primary for series or parallel, then I believe it is open. That is to say, the pads for one end of each input primary coil are not connected which allows you to decide whether to connect them in series or parallel (or to use a switch like several of us have).

Remember--if you ask for debugging help, please provide relevant info (which iron, which DOA, which options you used, etc.) so we can help.

A P

I used a sowter 9820 input transformer, a 2623-1 output transformer and 2520 opamp.

sorry for the blurry pics my camera phone is really bad hopefully it will help out though.

:?: Please guys it's passing audio I just need to know how to wire the pot correctly.

tie the wiper to the side coming from the op amp and the other side goes to the ground network. if it operates in reverse, reverse the leads to the pot. I have seen it happen when the output primary leads are reversed, it cancels out almost all the output audio.......

How do you know it's the gain control that is the problem? It looks like you wired the input iron to the pads with the color code labels. Again, the "grey" and "yellow" pads are isolated from everything else. You have to decide to wire the coils in series or parallel (or to a switch) and then connect those pads appropriately. Perhaps you inadvertently bridged grey and yellow on the working channel and therefore have them in series.

If the audio sounds "thin" you may have the problem described and solved in this thread a little while back:

http://www.groupdiy.com/index.php?topic=21341

If one channel seems to work you can compare it to the broken one and find the fault. I would start by measuring resistance between all the pins of the input primaries (white, grey, yellow, blue).

A P

I'm sorry AnalogPackrat but I really don't understand.

What is a a pad? The PCB board or the wires out of the transformer?

I don't understand bridged grey and yellow either or wire to a switch. Which switch?

The reason I think one of my opamps is bad is because I powered it down and switched the opamp of the one that wasn't working with the one that I was getting a signal through and I got the same faint signal through the other board.

The reason I'm thinking I have Gain knob wired wrong is because I can yell into the mic and see a level on the meters and it doesn't matter where I have the knob poistioned I get the same low level.

I honestly don't know if I'm getting a "thin" sound. I know I'm picking up alot of hum with the sound of me yelling. I recorded it and will post it if you think that will help.


Both channels seem to work when I swap opamps.

The resistance on the pins read as follows...

white, grey = 13.63 kiloohms

yellow, blue = 13.63 kiloohms

white, yellow = 47.3 ohms

grey, blue = 47.3 ohms

white, blue = 13.58 kiloohms

grey, yellow = 13.67 kiloohms

Thanks for the help.

Are you saying that I shouldn't be following the color codes on the board?

If so which colors do i tie together and where do I put them?

[quote author="bigwillz24"]I'm sorry AnalogPackrat but I really don't understand.

What is a a pad? The PCB board or the wires out of the transformer? [/quote]

The copper area around a thru hole where you solder a wire or component lead is called a solder pad.

I don't understand bridged grey and yellow either or wire to a switch. Which switch?

Click to expand...

I had assumed you had read the 312 meta. You can eaitehr hard wire your input transformer primary as a series connection of the two coils, a parallel connection, or you can wire them to a DPDT switch and select at will. It's all in the meta.

The reason I think one of my opamps is bad is because I powered it down and switched the opamp of the one that wasn't working with the one that I was getting a signal through and I got the same faint signal through the other board.

The reason I'm thinking I have Gain knob wired wrong is because I can yell into the mic and see a level on the meters and it doesn't matter where I have the knob poistioned I get the same low level.

Click to expand...

Does one of them work as you would expect with the "good" op amp? Do you get output levels like you would expect and full frequency range?

The resistance on the pins read as follows...

white, grey = 13.63 kiloohms

yellow, blue = 13.63 kiloohms

white, yellow = 47.3 ohms

grey, blue = 47.3 ohms

white, blue = 13.58 kiloohms

grey, yellow = 13.67 kiloohms

Click to expand...

Seems like you have the problem I described. You should see about 100ohms between white and blue if you wired the primaries in series or 25ohms if you wired them in parallel. What you seem to be seeing is the two 6k81 PP resistors in series with the coils. You had the phantom switched on, right? Try switching it off and you will read no continuity between white and blue or yellow and grey. For simplicity I recommend that you wire the primaries in series by soldering a short piece of buss wire (or leftover component lead off-cut) between the yellow and grey solder pads on the back of the board. Do it neatly and it will be easy to change later. Be careful not to bridge over to the white or blue pads.

This should solve at least part of your problem. It sounds like maybe you have a questionable op amp, too, but fix this first.

Thanks for the help.

Click to expand...

No problem. Hope you get it working.

A P

Okay I soldered the yellow and grey wires together like you said. The hum has disappeared and I no longer have to scream in the mic for it to work. It sounds good!

Now I'm still getting a signal with the gain knob all the way to the left and it doesn't seem to amplify or attenuate.

[quote author="AnalogPackrat"]

Seems like you have the problem I described. You should see about 100ohms between white and blue if you wired the primaries in series or 25ohms if you wired them in parallel. What you seem to be seeing is the two 6k81 PP resistors in series with the coils. You had the phantom switched on, right? Try switching it off and you will read no continuity between white and blue or yellow and grey. For simplicity I recommend that you wire the primaries in series by soldering a short piece of buss wire (or leftover component lead off-cut) between the yellow and grey solder pads on the back of the board. Do it neatly and it will be easy to change later. Be careful not to bridge over to the white or blue pads.

This should solve at least part of your problem. It sounds like maybe you have a questionable op amp, too, but fix this first.

A P[/quote]

I am now reading 14.6 ohms between the white and blue. 27ohms between the white and grey. 27ohms between the yellow and blue.

Okay I don't know what happened but now I have 64 volts on the phantom power and niether of the cards are passing audio anymore. :sad:

check your voltages from the psu. You might have blown a regulator.

Just so you know: Even when the gainknob is on the lowest setting the amp will still pass audio.

Are you using the Sowter input transformer?

If so: connect the yellow and blue wires in one hole (or just bridge the pads on the pcb), and white and gray wires in the other.

good luck!
/J

Disconnect all of your power connections to both cards and then turn on the PSU and check voltages. Tell us about the PSU. Is is Bauman's? What relay voltage are you running? Did you do any of the mods discussed in the meta? What power transformer are you using? Pretend like we don't know anything about your system...because we don't! Don't assume anything and let the data lead you to the problem and then a solution.

A P