[BUILD] 1176LN Rev D DIY

[Spencerleehorton]

ok well just tried 3.9k resistor in series on + of VU meter, input 0.775v and needle does nothing!!!
Im using the same Vu meters for both Rev A and Rev D so i'm assuming my problem is the Vu meters.
I would like to use these Vu meters but now need to figure out a way to get them working with the setup procedure also being correct!!!
first i need to establish what value these VU meters are!!!

 

[Spencerleehorton]

ok, now i've tried it directly connected to my MM and i'm getting a reading on the VU meter, set to ohms, the MM is reading 600ohms and the needle sits at -3db.
I have several other Vu meters and have tested all of them, the only one i can get sitting at 0db on diode mode is a sifam copy meter. this one reads 50ohms.
i do like the A&H style vu meters as i have about 20 of them!!! but i am perplexed as to what resistor to use for these as ratio wise if the Sifam copy is 50ohm and the other is 12 times as big (600ohms) should i try a 47K or does this have nothing to do with it?

 

[Spencerleehorton]

right, here goes replying to myself!!!

on further investigation i do remember on my Rev A changing the +8 and +4 (VU) resistors for trim pots (10k) on after thought i should probably have changed R67 3.9k which is the GR resistor for a 10k trim as well!!
tweaking the two R67 and R16 should hopefully give me the required amounts?
the only thing is, is there a way to roughly calculate what i should be looking for?

 

[scott2000]

47ohm in parallel with 600ohm will give you just under 50 ohms...... not sure what you are trying to say about the meter.....or the 47k

Changing resistors for trim pots shouldn't be an issue unless you wire them wrong. You can end up changing the pot start value to the resistor in series and the tapers can get wonky if they are wired a certain way????

Trying to follow better what you are doing so apologies for my rambling....

 

[alamine]

Hello,

several weeks ago I used my 1176 Rev D (ordered in September 2015)  with a faulty mixing desk and sent a signal with way too much gain to it.
I didn't notice it right away but I think the signal was going through the compressor for at least a minute before I turned it off.
The signal had such a high level that the metering light bulb started blinking and the needle was just sticking to the right side.

When I tested the compressor at home after that, it didn't work properly anymore.

1.) The compressor now outputs a fairly loud hum. (sounds like a mains hum) If I touch the chassis or the XLR jack it goes away. This might just be a ground loop in my setup at home but I didn't experience this before with other equipment.

2.) The gain reduction doesn't work like usual. It appears to be slower (not too sure if that's it), needs a higher level to start reducing gain and behaves really wonky overall.

3.) The meter behaves really strange. It doesn't detect any input until I crank the input knob all the way to the right.

4.) Audio Input and Output seem to be O.K.

I tried recalibrating the compressor but that didn't fix my problems.

I want to measure the control voltages shown in this file: http://mnats.net/files/1176REVD_VOLTS.pdf
but im an electronics noob and I'm really not sure how to do it. Where do I connect the second probe of my multimeter to measure these voltages?

What do you think did most likely break?


Regards, Adam

 

[Echo North]

Hello,

several weeks ago I used my 1176 Rev D (ordered in September 2015)  with a faulty mixing desk and sent a signal with way too much gain to it.
I didn't notice it right away but I think the signal was going through the compressor for at least a minute before I turned it off.
The signal had such a high level that the metering light bulb started blinking and the needle was just sticking to the right side.

When I tested the compressor at home after that, it didn't work properly anymore.

1.) The compressor now outputs a fairly loud hum. (sounds like a mains hum) If I touch the chassis or the XLR jack it goes away. This might just be a ground loop in my setup at home but I didn't experience this before with other equipment.

2.) The gain reduction doesn't work like usual. It appears to be slower (not too sure if that's it), needs a higher level to start reducing gain and behaves really wonky overall.

3.) The meter behaves really strange. It doesn't detect any input until I crank the input knob all the way to the right.

4.) Audio Input and Output seem to be O.K.

I tried recalibrating the compressor but that didn't fix my problems.

I want to measure the control voltages shown in this file: http://mnats.net/files/1176REVD_VOLTS.pdf
but im an electronics noob and I'm really not sure how to do it. Where do I connect the second probe of my multimeter to measure these voltages?

What do you think did most likely break?


Regards, Adam

Try running through the troubleshooting guide. See where you see issues.

http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

With that older unit, you're going to see some different voltages through the signal chain, but they should be roughly in the ball park.

Mike

 

[francesco vitaliti]

Hello
newbie here, and trying to calibrate my first 1176 rev D, it's based on an old kit (v2.2 pcb) and the only mod is orange drop cap instead of electrolytic on C1,C7,C8,C10.
But i'm having trouble in q bias calibration.
The trimmer is having very low influence on the output level, so i measured the dc to TP18 and values doesn't match (-5,48;-6,35).
I also checked the values of R59 after unsoldering and should be fine(1ohm:1,87 Kohm).
Any suggestions?

Thanks in advance

 

[Echo North]

Hello
newbie here, and trying to calibrate my first 1176 rev D, it's based on an old kit (v2.2 pcb) and the only mod is orange drop cap instead of electrolytic on C1,C7,C8,C10.
But i'm having trouble in q bias calibration.
The trimmer is having very low influence on the output level, so i measured the dc to TP18 and values doesn't match (-5,48;-6,35).
I also checked the values of R59 after unsoldering and should be fine(1ohm:1,87 Kohm).
Any suggestions?

Thanks in advance

CR2/CR3 oriented correctly?

 

[francesco vitaliti]

CR2/CR3 oriented correctly?

yep, stripe on the right side.

 

[Echo North]

yep, stripe on the right side.

You might want to pull them and test them with the diode tester on your meter.  Also make sure R35 and R60 are the correct value.

Mike

 

[francesco vitaliti]

Hi Mike,

You might want to pull them and test them with the diode tester on your meter.  Also make sure R35 and R60 are the correct value.

Mike

Diode CR2 and CR3 have no current flow in one direction, and reading of 0.817 and 0.792 in the other way when using the DMM in diode test, with a resistance of 20.5 K - 21k. Should be fine, right?
R35 and R60 correct value.

 

[francesco vitaliti]

Diode back in pcb, but still wrong values and q-bias adj is not affecting the output at all.
Just double checked the power supply and values are ok,  checked all the connections and looks good.
Any other suggestions?

 

[francesco vitaliti]

additional info: just checking the DC values and all the transistor works fine except Q12 and Q13 whose values are quite high (-4.4 G, 19.6 S, -2.4 D)

 

[Echo North]

additional info: just checking the DC values and all the transistor works fine except Q12 and Q13 whose values are quite high (-4.4 G, 19.6 S, -2.4 D)

Those need proper calibration to read correctly.

You have a ton of extra DC in your bias rail. If you remove CR2/3 what does Pad 18 read?

Mike

 

[francesco vitaliti]

Without Cr2 and 3 still having same value:
-5,43 with qbias adj CCW and -6,30 qbias adj CW. 

:-\  :'(

 

[Echo North]

Without Cr2 and 3 still having same value:
-5,43 with qbias adj CCW and -6,30 qbias adj CW. 

:-\  :'(

Check the value of R58, R61, R62, R63, R64.

Mike

 

[jefepeters]

Hello,

I'm attempting the calibrate the Q bias (using this procedure: http://www.hairballaudio.com/blog/resources/build-guides/calibration)

The input and output voltages are correct (0.775 and 2.75 VAC, respectively), but adjusting  R59 as no effect on either the VU reading or the output voltage.  Any suggestion on where I should start troubleshooting?

Thanks,
Justin

 

[Echo North]

Hello,

I'm attempting the calibrate the Q bias (using this procedure: http://www.hairballaudio.com/blog/resources/build-guides/calibration)

The input and output voltages are correct (0.775 and 2.75 VAC, respectively), but adjusting  R59 as no effect on either the VU reading or the output voltage.  Any suggestion on where I should start troubleshooting?

Thanks,
Justin

Most of this applies:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

What are your QBias voltages?

 

[jefepeters]

Most of this applies:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

What are your QBias voltages?

The initial voltage was -1.1 and I could twist it CCW to -2.4 VDC. What is considered the "extreme of the pot"? When I turn it, there is no obvious point where I feel it stiffen up.  I turned it  until I heard a click, but nothing was stopping me from turning it further.

The range of travel is 25 turns (per https://www.mouser.com/ds/2/54/299-776927.pdf), correct?

 

[Echo North]

The initial voltage was -1.1 and I could twist it CCW to -2.4 VDC. What is considered the "extreme of the pot"? When I turn it, there is no obvious point where I feel it stiffen up.  I turned it  until I heard a click, but nothing was stopping me from turning it further.

The range of travel is 25 turns (per https://www.mouser.com/ds/2/54/299-776927.pdf), correct?

20 or 25, I can't remember. The click is the end.

It should go down to 0 VDC, that is your issue. Until you can get it below -1 VDC you are not going to see much compression.  CR2/CR3 in the right orientation?  What are you Pad 21 voltages per the guide?

Mike