Thanks for the response, I went through the steps on your other video but getting no change in my q-bias trimmer pot. I have a feeling that the trimmer pot is not functioning since I tested it turned both way and getting the same reading. This is also happening on my null adjustment. The other two trimmer pots seem to function fine with a multimeter. The only strange thing here is that the trimmer pots are malfunctioning and functioning exactly the same on both units. I guess I will get some new trimmer pots and see if that fixes it. Thanks again for the help!
For the qbias adjustment - yes. The part numbers on the board may differ but the steps are the same. For the meter calibrations, that applies only to the DIY Revision A and D boards with the discrete transistor meter circuit.
Yes, carefully hook up the POWER transformer as per MNATS wiring instructions and carefully test that you are getting the correct AC from the transformer before hooking it up to the board. Once you know that the power transformer is delivering the correct AC you can then hook it up to the power section of the PCB and test those points you mentioned as DC on your volt meter. No need to hook up ANYTHING else at this point. Be careful to wire your transformer correctly and you'll be fine.
At this stage, when everything seems confusing, unplug the unit and take a break! Then, with the unit UNPLUGGED (no power connected) run some audio or a test tone into the unit. The input goes to the t-pad input knob, into the input xformer and into the PCB - at the point where the input connects to the PCB you should be able to detect a signal. Grab an OLD pair of headphones and touch the tip on the pad where the xformer connects to the PCB - slowly turn up the input and to detect audio.
Hey Don I'm really having a problem with my 1176 RevD Im getting some feedback Im really not sure where to check for where the problem is. Is there any way I can get you to actually look at mine?
Thanks for a answer, i was able to trace my loud output from XLR, (unit shut down ofcourse) from Input transformator to pcb (i had to take of the ground and + from pcb, it detects sound. Very low volume. not even a high volume turned the t-attenuator knob to fullest..Should it be like this? (the t-attenuator is reacting to my turns on the knob)
Hi Don, I did the cal as you describe here. First I think I broke the stock trim pot 2k turning way more because the resistance was always 2 ohms. So both a similar one and did the cal with that. But the problem is I have very low gain when I open the unit, after 15 mins I get a very high input maybe a normal one. For 0.775 input I have 25 V output with attack off. With that gain I could make as you described here. I thought I got the bias now. But when I am tracking, it gets suddenly very low ( like output 1.6 max ) and again jump to the gain I got before with a strong ring. Can you guess where the problem might be. I checked the legs of q trim, no short seems there but can there be a trimpot problem or some other component problem in the circuit that is gain affecting (at 20:1 and attack off setting)
Hi Don, What type of trimmers are you using? Mine look exactly the same but do not tighten and stop but keep turning while clicking once at the end. I was told by mouser this was the way they are supposed to function but having a hard time calibrating my two units(both have the same exact problem). I get a nice signal in and out but get no change in the vu when I turn the q-bias. I measured all the trim pots and it looks about half of them do not stay at a specific reading but are gradually going up. The others are reading the way you specified in the video. Could I have some how blown them while soldering them to the board? I am also using a Pro tools signal generator for the calibration process. I have been trying to figure out this issue for some time now so thanks in advance for any help you can give me. Jeff
yeah, some of the better ones "click" at the extremes. try this trick to get the qbias right: 1176 qbias - trick to get it right Very unlikely you have hurt anything related to the trims while soldering.
Okay! thank you for the answer, my apologies for asking so much. I feel like i am the only one building a Rev F and could not find these answers anywhere else. Alright, that´ll be my next step then!, I ordere the Rev F kit from Hairball Audio with the Ed Andersson & Avel Lindberg transformers. If i have read it correctly you can use the wiring page for the the wires of these power transformers, right? Thnks in beforehand!
Okay thanks, i just got my parts and i just soldered the components on the power supply section on the PCB. Do i have to assemble the transofmers etc first to see if the power supply is working properly before soldering the other compoonents? Or is there a way to check with the DMM that everything is alright? i just checked the current between CT -> -10V & + 30V and it gave me 810 on the -10, and about 1840 on the + 30.
Hi again Don! Well i am done with my Rev F now, but i have one queston and one issue. My question follows: The calibrations, Which are necessary for the Rev F ? Only Q-Bias and the Zero Adj?I became a registered user in GroupDIY and have read the Rev F thread.i asked some questions but the thread seems to be dead..Then my issue, i dont get ANY signal going through the Input XLR..altough im feeding all sorts of signal. No compression nothing..net even sound out from the output xlr..whats wrong?
Okay so ive completed all the other parts now i just need to fill the board with all the components..But still, i cannot get the readings right between CT -10 & 30 V, altough i have resoldered every component in that section to be sure that there is no cold solderings etc. I could get near 10 V on the 10v pad, but no life between CT - 30 V.. Is this normal? Every video ive checked up is about the Rev D. maybe i just should go and get that board and components instead.The impatience is growing
Hey Don, so i allowed your video step by step only problem is my Q bias resistor is click when i turn it passed a certain point in either direction. So once i've got the meter to +1 dialing the resistor back doesn't seem to do anything. Is my Q bias resistor messed up?
set your DMM to measure AC and put your leads on pins 2 and 3 on the output - with your .775 volt/1k input signal being fed into the unit adjust the input to at least half way up, then slowly turn up the output and watch the DMM voltage rise until it hits about 2 volts. Now twist the q-bias and see if you can see a change in the output voltage - either up or down makes no difference. I just want to know if changing the qbias effects the output voltage, which is should. For now ignore the meter on the front of the unit.
Don Bonin ok so I did that first the output at pin 2 and 3 is reading about 1.5 thats with the input set to 12 on the dial, and the output all the way up, the ratio is 20;1 the meter is set to +4. Im using logics signal generator could that be an issue? I'm using a 1k Signal at -12dB, going from logic 9 through my scarlett 18i20 to the input of the 1176. When i change the q bias nothing happens at the output. I have a Rev D is it different for the Rev D?
I have the exact same problem. Q-bias not reacting and DMM not dropping or increasing when I try what you suggest here. I have changed the q-bias but with the same result. What affects the q-bias? Can I change any components around the q-bias. Is it the wiring. Any suggestions? Ive recently soldered the C* C* C*2 and C*3 on the board. Not using any input. When I measure all the Q-points according to the schematic I get the right volt everywhere.
PS: Maybe the transformer is not providing the right AV altough its tagged as Passed, or maybe the circuit board has broken for some reason. Im 100 % sure ive soldered the components the right way, and the right direction.
Don, thanks so much for these videos! Very useful. I'm having some problems with my rev. d 1176 build and was wondering if you could help me out via Skype? I posted over on the group DIY forum.
Thanks for the response, I went through the steps on your other video but getting no change in my q-bias trimmer pot. I have a feeling that the trimmer pot is not functioning since I tested it turned both way and getting the same reading. This is also happening on my null adjustment. The other two trimmer pots seem to function fine with a multimeter. The only strange thing here is that the trimmer pots are malfunctioning and functioning exactly the same on both units. I guess I will get some new trimmer pots and see if that fixes it. Thanks again for the help!
For the qbias adjustment - yes. The part numbers on the board may differ but the steps are the same. For the meter calibrations, that applies only to the DIY Revision A and D boards with the discrete transistor meter circuit.
Yes, carefully hook up the POWER transformer as per MNATS wiring instructions and carefully test that you are getting the correct AC from the transformer before hooking it up to the board. Once you know that the power transformer is delivering the correct AC you can then hook it up to the power section of the PCB and test those points you mentioned as DC on your volt meter. No need to hook up ANYTHING else at this point. Be careful to wire your transformer correctly and you'll be fine.
At this stage, when everything seems confusing, unplug the unit and take a break!
Then, with the unit UNPLUGGED (no power connected) run some audio or a test tone into the unit. The input goes to the t-pad input knob, into the input xformer and into the PCB - at the point where the input connects to the PCB you should be able to detect a signal. Grab an OLD pair of headphones and touch the tip on the pad where the xformer connects to the PCB - slowly turn up the input and to detect audio.
Hey Don I'm really having a problem with my 1176 RevD Im getting some feedback Im really not sure where to check for where the problem is. Is there any way I can get you to actually look at mine?
Thanks for a answer, i was able to trace my loud output from XLR, (unit shut down ofcourse) from Input transformator to pcb (i had to take of the ground and + from pcb, it detects sound. Very low volume. not even a high volume turned the t-attenuator knob to fullest..Should it be like this? (the t-attenuator is reacting to my turns on the knob)
Cool - the power section is the same no matter what rev you are building.
Hi Don, I did the cal as you describe here. First I think I broke the stock trim pot 2k turning way more because the resistance was always 2 ohms. So both a similar one and did the cal with that. But the problem is I have very low gain when I open the unit, after 15 mins I get a very high input maybe a normal one. For 0.775 input I have 25 V output with attack off. With that gain I could make as you described here. I thought I got the bias now. But when I am tracking, it gets suddenly very low ( like output 1.6 max ) and again jump to the gain I got before with a strong ring. Can you guess where the problem might be. I checked the legs of q trim, no short seems there but can there be a trimpot problem or some other component problem in the circuit that is gain affecting (at 20:1 and attack off setting)
Thats a REVA by the way. And while the gain was high I got a great sound too from the box. So thought really it was done till the gain drop :)
Hi Don, What type of trimmers are you using? Mine look exactly the same but do not tighten and stop but keep turning while clicking once at the end. I was told by mouser this was the way they are supposed to function but having a hard time calibrating my two units(both have the same exact problem). I get a nice signal in and out but get no change in the vu when I turn the q-bias. I measured all the trim pots and it looks about half of them do not stay at a specific reading but are gradually going up. The others are reading the way you specified in the video. Could I have some how blown them while soldering them to the board? I am also using a Pro tools signal generator for the calibration process. I have been trying to figure out this issue for some time now so thanks in advance for any help you can give me.
Jeff
yeah, some of the better ones "click" at the extremes. try this trick to get the qbias right: 1176 qbias - trick to get it right
Very unlikely you have hurt anything related to the trims while soldering.
Okay! thank you for the answer, my apologies for asking so much. I feel like i am the only one building a Rev F and could not find these answers anywhere else. Alright, that´ll be my next step then!, I ordere the Rev F kit from Hairball Audio with the Ed Andersson & Avel Lindberg transformers. If i have read it correctly you can use the wiring page for the the wires of these power transformers, right? Thnks in beforehand!
Okay thanks, i just got my parts and i just soldered the components on the power supply section on the PCB. Do i have to assemble the transofmers etc first to see if the power supply is working properly before soldering the other compoonents? Or is there a way to check with the DMM that everything is alright? i just checked the current between CT -> -10V & + 30V and it gave me 810 on the -10, and about 1840 on the + 30.
Hi again Don! Well i am done with my Rev F now, but i have one queston and one issue. My question follows: The calibrations, Which are necessary for the Rev F ? Only Q-Bias and the Zero Adj?I became a registered user in GroupDIY and have read the Rev F thread.i asked some questions but the thread seems to be dead..Then my issue, i dont get ANY signal going through the Input XLR..altough im feeding all sorts of signal. No compression nothing..net even sound out from the output xlr..whats wrong?
Okay so ive completed all the other parts now i just need to fill the board with all the components..But still, i cannot get the readings right between CT -10 & 30 V, altough i have resoldered every component in that section to be sure that there is no cold solderings etc. I could get near 10 V on the 10v pad, but no life between CT - 30 V.. Is this normal? Every video ive checked up is about the Rev D. maybe i just should go and get that board and components instead.The impatience is growing
Note: The Rev F/G uses LM317 regulator and a resistor, instead of 7824 in PSU. But otherwise, yes they are the same.
Are these calibrations/adjustments necessary for the Rev F also ?
Hey Don, so i allowed your video step by step only problem is my Q bias resistor is click when i turn it passed a certain point in either direction. So once i've got the meter to +1 dialing the resistor back doesn't seem to do anything. Is my Q bias resistor messed up?
set your DMM to measure AC and put your leads on pins 2 and 3 on the output - with your .775 volt/1k input signal being fed into the unit adjust the input to at least half way up, then slowly turn up the output and watch the DMM voltage rise until it hits about 2 volts. Now twist the q-bias and see if you can see a change in the output voltage - either up or down makes no difference. I just want to know if changing the qbias effects the output voltage, which is should. For now ignore the meter on the front of the unit.
Don Bonin ok so I did that first the output at pin 2 and 3 is reading about 1.5 thats with the input set to 12 on the dial, and the output all the way up, the ratio is 20;1 the meter is set to +4. Im using logics signal generator could that be an issue? I'm using a 1k Signal at -12dB, going from logic 9 through my scarlett 18i20 to the input of the 1176. When i change the q bias nothing happens at the output. I have a Rev D is it different for the Rev D?
after trying it with the DMM I have i don't think I'm getting very accurate readings I'm going to try it with a better one
Kirk Cosier ok, please let me know how it goes. Also, please contact me via don.bonin@gmail.com for a more timely reaponse.
I have the exact same problem. Q-bias not reacting and DMM not dropping or increasing when I try what you suggest here. I have changed the q-bias but with the same result.
What affects the q-bias? Can I change any components around the q-bias. Is it the wiring. Any suggestions?
Ive recently soldered the C* C* C*2 and C*3 on the board. Not using any input.
When I measure all the Q-points according to the schematic I get the right volt everywhere.
PS: Maybe the transformer is not providing the right AV altough its tagged as Passed, or maybe the circuit board has broken for some reason. Im 100 % sure ive soldered the components the right way, and the right direction.
Don, thanks so much for these videos! Very useful. I'm having some problems with my rev. d 1176 build and was wondering if you could help me out via Skype? I posted over on the group DIY forum.
Please send me a private message over on the DIY forum and I'll help you out. We can set up a time to troubleshoot together via skype if you want.
Thanks so much, I sent you a PM there.