I’ve just finished the assembly of the VU2 kit,
Meter lights work, meters move very slightly on turn on,
But,
No response to input signal.
I’m using balanced inputs driven for testing with a Neutrik Minirator.
+4 DB gives nothing, I’ve adjusted the trim pots and still nothing.
Any suggestions on where to start trouble shooting?
Also what sort of voltage would I expect to measure from the meter outputs ?
Thanks,
Blake
What meters are you using with the VU2 kit?
Do you have diodes fitted to the VU2 or not?
Send me some photos of the VU2 top and bottom and wiring to the meters and 12v power to check for you.
I have not added any diodes to the meter or between the meter and the VU2.
The meters have functioned with a couple of other brands of driver board,
But the Boards were unbalanced and introduced hum into the system.
The VU2 is powered from a regulated 12v board,
The lamps in the meters light up fine with the bypass resistor. They came supplied with their own to put in parallel with the meter lights.
I have several other meters I’ll try out.
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Just got mine assembled and am having an issue. Possible user error as I didn't notice that R2R and R2L weren't installed before powering up. Both meter outputs showed around 0.2 DC volts regardless of input. Once I did notice the missing resistors and installed them, not much changed. Meter output voltage dropped in half is still basically invariable to input. I'm pretty sure I've turned the POTs enough and even tried replacing R7 with a lower value.
Did I damage the opamp or is there some other basic debug I should start with?
Just got mine assembled and am having an issue. Possible user error as I didn't notice that R2R and R2L weren't installed before powering up. Both meter outputs showed around 0.2 DC volts regardless of input. Once I did notice the missing resistors and installed them, not much changed. Meter output voltage dropped in half is still basically invariable to input. I'm pretty sure I've turned the POTs enough and even tried replacing R7 with a lower value.
Did I damage the opamp or is there some other basic debug I should start with?
The buffer outputs have a cap so no dc can make it to the meter. Leaving those resistors out will not damage anything. Best first to send me some photos of the wiring and setup you have so I can see if I can spot the problem. Otherwise, as always top and bottom photos of the pcb helps to check for problems as well.
The buffer outputs have a cap so no dc can make it to the meter. Leaving those resistors out will not damage anything. Best first to send me some photos of the wiring and setup you have so I can see if I can spot the problem. Otherwise, as always top and bottom photos of the pcb helps to check for problems as well.
Top Side. Not using lamp power, so no RLAMP resistors.
Bottom Side
XLR's tied together on PCB. (Blue goes to red, white to white, sleeve to sleeve)
Input end. Looks messy, but verified conductors are not shorted.
The buffer outputs have a cap so no dc can make it to the meter. Leaving those resistors out will not damage anything. Best first to send me some photos of the wiring and setup you have so I can see if I can spot the problem. Otherwise, as always top and bottom photos of the pcb helps to check for problems as well.
Looks fine. Not sure if that 24v is tied to the same 0v as the power amp voltage. You should be able to measure the ohms across the gain pot on the buffer with the buffer off. Takes 25 full turns end to end.
What meters are you running as they may have an internal resistor and/or diode bridge?
Looks fine. Not sure if that 24v is tied to the same 0v as the power amp voltage. You should be able to measure the ohms across the gain pot on the buffer with the buffer off. Takes 25 full turns end to end.
What meters are you running as they may have an internal resistor and/or diode bridge?
I measured the pots and they are fully open, close to 0 ohms. I'm using some eBay Chinese 34mm round vu meters. I'm pretty sure these are all functionally the same?
I checked the other components on the board and they all seem to measure fine.
Please forgive my limited electronics knowledge, but at suggestion of Google I put the TL072 on a breadboard and put it in voltage follower mode. With VCC+ 12v and VCC- to ground I'm getting +12v output whether the non-inverting input is either 12v or ground. Is that the expected behavior? Is behaves the same on both sides of the IC.
Looks fine. Not sure if that 24v is tied to the same 0v as the power amp voltage. You should be able to measure the ohms across the gain pot on the buffer with the buffer off. Takes 25 full turns end to end.
What meters are you running as they may have an internal resistor and/or diode bridge?
I measured the pots and they are fully open, close to 0 ohms. I'm using some eBay Chinese 34mm round vu meters. I'm pretty sure these are all functionally the same?
I checked the other components on the board and they all seem to measure fine.
Please forgive my limited electronics knowledge, but at suggestion of Google I put the TL072 on a breadboard and put it in voltage follower mode. With VCC+ 12v and VCC- to ground I'm getting +12v output whether the non-inverting input is either 12v or ground. Is that the expected behavior? Is behaves the same on both sides of the IC.
The VU buffer pcb makes a half voltage rail reference for the TL072. So all the pins of the TL072 except pin 4 = 0v and pin 8 = V
So your setup measured from 0v on the buffer pcb pin 1,2,3,5,6,7 = 12v and pin 4 = 0v and pin 8 = 24v. Let me know if the voltages are correct on all pins of the TL072
The VU buffer pcb makes a half voltage rail reference for the TL072. So all the pins of the TL072 except pin 4 = 0v and pin 8 = V
So your setup measured from 0v on the buffer pcb pin 1,2,3,5,6,7 = 12v and pin 4 = 0v and pin 8 = 24v. Let me know if the voltages are correct on all pins of the TL072
Pins 1, 4, 7, 8 look correct. 3,5 are low and 2,6 are high
The VU buffer pcb makes a half voltage rail reference for the TL072. So all the pins of the TL072 except pin 4 = 0v and pin 8 = V
So your setup measured from 0v on the buffer pcb pin 1,2,3,5,6,7 = 12v and pin 4 = 0v and pin 8 = 24v. Let me know if the voltages are correct on all pins of the TL072
Pins 1, 4, 7, 8 look correct. 3,5 are low and 2,6 are high
The opamp and power are working fine as pin 1 and pin 7 outputs are still at 12v. The rest are a bit out because you have the gain fully cranked which for a XLR input should be way too much gain. Something is wrong with the input or the meter wiring. You do have the meter going to +M-? and remember if they are reversed the meter it will push downwards which you can be hard to see as it will not move far. I would wire the meter directly to the input XLRs without the amps and see if you can get the meters working on their own without the amp input attached.
The opamp and power are working fine as pin 1 and pin 7 outputs are still at 12v. The rest are a bit out because you have the gain fully cranked which for a XLR input should be way too much gain. Something is wrong with the input or the meter wiring. You do have the meter going to +M-? and remember if they are reversed the meter it will push downwards which you can be hard to see as it will not move far. I would wire the meter directly to the input XLRs without the amps and see if you can get the meters working on their own without the amp input attached.
Joe,
Thankyou for being so patient with me. I tried hooking up the xlrs directly to the meters and was pleasantly surprised that that even works. Now, it didn't really do anything until I cranked my source to near 0 dB, but it was promising to see. (Curiously, at that level the meter starts to act like a speaker of sorts. You can actually hear it playing.)
Now comes the part where I admit to being an idiot . After that experiment I was convinced that the buffer had to be working. Turns out it was all along, at least, I'm pretty sure. After turning my source up a decent bit louder than expected, suddenly there was movement on the meters. The problem before was that I was attempting to adjust the buffer while listening to music with the amp on and connected to speakers. Naturally, I didn't turn it up very loud because I was right on top of the speakers. There seems to be a minimum input threshold where the buffer doesn't really do much of anything and I was simply never reaching that point.
I may still play around with some resistor values to see if I can drive the meters at lower listening levels, but at least now I know things aren't completely broken.
The opamp and power are working fine as pin 1 and pin 7 outputs are still at 12v. The rest are a bit out because you have the gain fully cranked which for a XLR input should be way too much gain. Something is wrong with the input or the meter wiring. You do have the meter going to +M-? and remember if they are reversed the meter it will push downwards which you can be hard to see as it will not move far. I would wire the meter directly to the input XLRs without the amps and see if you can get the meters working on their own without the amp input attached.
Joe,
Thankyou for being so patient with me. I tried hooking up the xlrs directly to the meters and was pleasantly surprised that that even works. Now, it didn't really do anything until I cranked my source to near 0 dB, but it was promising to see. (Curiously, at that level the meter starts to act like a speaker of sorts. You can actually hear it playing.)
Now comes the part where I admit to being an idiot . After that experiment I was convinced that the buffer had to be working. Turns out it was all along, at least, I'm pretty sure. After turning my source up a decent bit louder than expected, suddenly there was movement on the meters. The problem before was that I was attempting to adjust the buffer while listening to music with the amp on and connected to speakers. Naturally, I didn't turn it up very loud because I was right on top of the speakers. There seems to be a minimum input threshold where the buffer doesn't really do much of anything and I was simply never reaching that point.
I may still play around with some resistor values to see if I can drive the meters at lower listening levels, but at least now I know things aren't completely broken.
Regards,
Kevin
Yes is always best to run VU meters and the buffer of pre volume level as the meter only shows 23dB range so after the volume will only work for a small range of the volume control.
I purchased two VU buffer kits with the intent of using the original Radiomixer's VU Meter Bridge in conjunction with my existing setup. I've gutted the Radiomixers of all their original parts, except for the VU meter bridges, and I am in need of some assistance.
Below is a link to a photo of the VU meters in question. They are labeled with these markings: SIFAM 1.734V Ext 3K6 NO. 54997/3 -010B S24 I'll also add the photo as an attachment if the link does not load or vise versa.
. After that experiment I was convinced that the buffer had to be working. Turns out it was all along, at least, I'm pretty sure. After turning my source up a decent bit louder than expected, suddenly there was movement on the meters. The problem before was that I was attempting to adjust the buffer while listening to music with the amp on and connected to speakers. Naturally, I didn't turn it up very loud because I was right on top of the speakers. There seems to be a minimum input threshold where the buffer doesn't really do much of anything and I was simply never reaching that point.