[BUILD] 1176LN Rev D DIY

[Echo North]

Hey guys,


I just finished building a Rev D a few days ago. It worked perfectly ofr about 2 days, but now when I fired it up, the VU meter light bulb doesn't seem to work. The sound still sounds the same though. Nothing else weird going on so I suspect it's just the light bulb? How can this get broken by just sitting there? Would there be something wrong with my wiring? I would suspect not.. How can I fix this? Add 2 colored leds at the back of the VU meter?


Thanks in advance! I'll be buying some more kits in the near future for sure!


Mr.Franky

What is the V across the lamp pins?  Should be about 11VAC.  If that's what it is probably just  bad lamp.

You can string two LEDs in series across the lamp holder but you'll need to drop the voltage.

I can send you a new lamp.

Mike

 

[dbonin]

OK-first off, thank you guys SO much for helping us all out with our 1176s!

so i got both of mine working, and passing signal. i got thru the 1st two steps of calibration, however, i'm not having problems. 2 questions:

1-if i sweep my release pot from L to R, i get a huge sweep on the meter. even at GR, it will sweep from full L to pegged in the red. is this normal?

2-in step 3, when i disengage the comp(i've got the attack pot "off" function; should i be doing the 22 pad jumper to ground thing as well?), and the input level is set to 0, i get NO drop in DBs on the meter. it stays at 0. what am i doing wrong here? no combination of pad 22 jumper and comp disengaged will show a drop of 10db, not even 2db!

thanks again for the help, getting close!!!

Make sure you don't have the output and release pots swapped - if they ARE swapped you will typically get through the first two calibrations but not be able to do the final meter calibration.  Ask me how I know this.  :
To check the pots AFTER they are wired up  and attached to the face plate, just set your dmm to measure resistance and put your test leads on the middle wiper and one of the outside wipers - turn the knob all the way to each extreme and note the largest resistance reading for each of the pots.  The OUTPUT pot should read close to 250 k if it is the correct pot.  NOTE!...  to test this properly, disconnect the output pot from where it is wired to the PCB (if using terminal connects) - if you are hard wired to the PCB your resistance will read LESS than 250k on the pot at the highest setting. That's normal.  If you are wired up completely and you measure 250k on the output pot you have the WRONG POT on the output.

 

[Echo North]

<You could try hitting all of the solder joints in that section to try and eliminate a cold joint.>

Good advice. I retouched every solder joint in the GR section, and also removed the GR "0" set trimpot and tested it too, works fine, reinstalled. Even confirmed continuity between every soldered connection in the GR meter driver!

<Which voltages are a little high?>

I'm getting 11.37VDC instead of 10.56VDC on Q11. Since the meter is driven by a differential voltage, all that seems to matter is the differential between X and Y.
The GR meter voltages are +/-10% out in several places with R44 in circuit, but look perfect when it's not in circuit (null mode). And I'm able to null the meter perfectly.

I'm starting to suspect the problem is not in the GR meter driver, but the voltage Q11 is being sent by the GR control amp via R56. What voltage should I be seeing at R65 or Q11 when in GR mode with no input? Just to be 100% sure, I went through the meter null and Q bias adjustments again, confirmed they are all done correctly. Seems like I have to turn up the input pretty high to get -10dB GR with a 0.775VAC 1kHz test signal. It's on 9 (in between 6 and 12). Did the exact same test on my bluestripe. I'm getting -10dB GR with the input on 17. Output on both units is almost the same (48).

I've confirmed all the resistors in the GR control amp and meter driver are correct. Have not checked out the ratio board though. I can't find a drawing of that PCB or a pic online unstuffed, so I can see what the values are supposed to be on the PCB. That would be very handy at this point.

Any other ideas where I should look? Thanks!

Setting it to 9 is WAY high.  Maybe there is a larger issue?

Are you passing signal?  If you measure the output in bypass and then hit GR are you seeing reduction on the output?

I wonder if there is an issue in the GR amp itself.  Double check all of the wiring and check the voltages in the GR amp.

Let's get this sorted! 

 

[Echo North]

I'd be very curious to see what the voltages that set the threshold in the GR amp are doing.  If you need help with that let me know.

 

[Echo North]

If you're only getting say -5dB of reduction at the output with the input that high, then there is an issue with the ratio board (threshold) and or GR amp voltage.

Ok I'll stop rambling!

 

[rjd2rjd2]

ok, two things seem off for me:

1-the lowest "offset" i can get at the release pot is a differential of about 2-3db. with the zero adjust pot all the way CCW, a full sweep of the release pot will move the meter about 3db. zero adjust pot at fully CW, a full release pot sweep will move the meter from L to R completely. if i do step 2 with the jumper in place, and disregarding voltage at R74, i can ALMOST get the meter to zero out and only have the release pot cause a 2-3db change in meter with a full sweep of release pot.

2-i don't seem to get any drop in DB when engaging the comp via attack pot. if i engage the comp, with an input/outpit signal that would be at zero with the meter at +4, i don't HEAR any drop in gain, nor do i SEE a drop in gain when checked via meter at GR.

i have quadruple checked my wiring. its all right. the only possible thing i'm unsure of is the R value across the pins of the release pot- i can't seem to find that in the BOM, so i code matched off the wiring notes.

should my first order of operations be to get voltages in the GR section of the PCB against the voltages i should be seeing? thanks for the help.

 

[dbonin]

For rev D:

R57 on RELEASE pot "270k" "Resistor - 1/4 Watt
R54 Located on Attack Pot "470R" "Resistor - 1/4 Watt

Mike has a document listing all the ratio resistor values here:
http://www.hairballaudio.com/docs/FET%20Compressor%20PCB%20Board%20Info%20V3.pdf

I'm also curious why you are moving the release pot for anything to do with calibration - i set it to full CW position for all three calibrations.  Did you mean to say attack pot?

ok, two things seem off for me:

1-the lowest "offset" i can get at the release pot is a differential of about 2-3db. with the zero adjust pot all the way CCW, a full sweep of the release pot will move the meter about 3db. zero adjust pot at fully CW, a full release pot sweep will move the meter from L to R completely. if i do step 2 with the jumper in place, and disregarding voltage at R74, i can ALMOST get the meter to zero out and only have the release pot cause a 2-3db change in meter with a full sweep of release pot.

2-i don't seem to get any drop in DB when engaging the comp via attack pot. if i engage the comp, with an input/outpit signal that would be at zero with the meter at +4, i don't HEAR any drop in gain, nor do i SEE a drop in gain when checked via meter at GR.

i have quadruple checked my wiring. its all right. the only possible thing i'm unsure of is the R value across the pins of the release pot- i can't seem to find that in the BOM, so i code matched off the wiring notes.

should my first order of operations be to get voltages in the GR section of the PCB against the voltages i should be seeing? thanks for the help.

 

[AusTex64]

<Setting it to 9 is WAY high.  Maybe there is a larger issue?> Agreed!

<Are you passing signal?>  Yes

<If you measure the output in bypass and then hit GR are you seeing reduction on the output?> Yes. With .775VAC 1kHz tone (0dBu) on input, meter reads 0 on +4 setting, I'm getting 1.223VAC (+4dBu) on output with GR bypassed. With GR engaged,  I get .410VAC, which is -5.53dBu, so about -9.5dB gain reduction on output.

<I wonder if there is an issue in the GR amp itself.> Checked all resistors, even lifted one leg and measured each. All are correct.  Additionally, we checked the ratio board resistors too, all are correct.

<Double check all of the wiring> Will do that next.

<check the voltages in the GR amp.> Did that. Voltages are pretty close, but not exact.

Q7 - 14.75, 4.47, 3.92
Q8 - 14.2
Q9 - 16.94, 3.39, 2.83
Q10 - 16.37

Also replaced all four transistors with HFE tested good parts, just to rule that out. In fact, I've confirmed tonight that every resistor and cap on the main PCB is correct.

In the signal preamp, all voltages were perfect except 11.59 on Q3 (should be 12.58) and 11V out from Q14 (should be 12V).


<Let's get this sorted!  > I'm ready!!!

 

[rjd2rjd2]

For rev D:

I'm also curious why you are moving the release pot for anything to do with calibration - i set it to full CW position for all three calibrations.  Did you mean to say attack pot?

thanks for the help. nope-i meant release. i tried doing the calibration with the release pot CW, but i couldnt get anywhere on the tracking step, cause of the non-GR issue stated previously, so i swept the release pot just to see if it would change anything about the calibration procedure. and sure enough, it had a BIG effect on the meter portion.

i was moving the release pot because i noticed the issue of the release pot sweeps making the needle go nuclear, and it seems like "well if it's going to do that to the meter in normal usage, what's the point of even having a zeroed meter in normal usage conditions?" is a 3db nudge normal?

just to clarify, the jumper pin should be in normal/"high" position for step 1, bypass/"low" position for step 2, and then normal position again for step 3, right?

 

[dbonin]

For rev D:

I'm also curious why you are moving the release pot for anything to do with calibration - i set it to full CW position for all three calibrations.  Did you mean to say attack pot?

thanks for the help. nope-i meant release. i tried doing the calibration with the release pot CW, but i couldnt get anywhere on the tracking step, cause of the non-GR issue stated previously, so i swept the release pot just to see if it would change anything about the calibration procedure. and sure enough, it had a BIG effect on the meter portion.

i was moving the release pot because i noticed the issue of the release pot sweeps making the needle go nuclear, and it seems like "well if it's going to do that to the meter in normal usage, what's the point of even having a zeroed meter in normal usage conditions?" is a 3db nudge normal?

just to clarify, the jumper pin should be in normal/"high" position for step 1, bypass/"low" position for step 2, and then normal position again for step 3, right?

The jumper at r69 only need to be off for the second calibration step and on for everything else.

Are you 100% sure your output pot is the 250k and your release pot is the 5M?

 

[rjd2rjd2]

OK-got full voltage readings per the mnats voltage sheet. signal preamp section looks roughly right, but GR meter driver and GR control amp don't look right. i can post full voltages in a minute, but i noticed one thing right away:

where R79, R67, and Q11 meet, the voltage should be 10.56V,but i'm only getting about 2.2 V there. i never saw this in the build notes, but on this voltage sheet, is says "R77 not used in rotary switch version". i'm doing the rotary switch version, so do i jumper, or just remove it? hope this solves my problems!

EDIT: problem not solved. removed 8.2k R77 from meter board, still see 2.1V downstream of R79.

i checked-R79, R67, and R74 are all verified proper values(15k, 3.9K, 2.7M respectively). i socketed Q11. if i REMOVE Q11 from the circuit, this point where R79-R67-Q11 meet reads 13V. if i seat Q11, it drops back to 2.1V. i doubt it is a bad transistor, as i have tried a brand new 2n5457 and i get the same results.

any ideas? (Dbonin-yes, release pot is definitely 5Meg pot, thanks)

 

[mnats]

i checked-R79, R67, and R74 are all verified proper values(15k, 3.9K, 2.7M respectively). i socketed Q11. if i REMOVE Q11 from the circuit, this point where R79-R67-Q11 meet reads 13V. if i seat Q11, it drops back to 2.1V. i doubt it is a bad transistor, as i have tried a brand new 2n5457 and i get the same results.

What is the gate voltage of Q11?

 

[rjd2rjd2]

i checked-R79, R67, and R74 are all verified proper values(15k, 3.9K, 2.7M respectively). i socketed Q11. if i REMOVE Q11 from the circuit, this point where R79-R67-Q11 meet reads 13V. if i seat Q11, it drops back to 2.1V. i doubt it is a bad transistor, as i have tried a brand new 2n5457 and i get the same results.

What is the gate voltage of Q11?

when Q11 is seated:
D=6.6V
S=.9V
G=.03V

A little more info: on BOTH sides of R74, i am measuring 2.1V; looks like i should be reading about 9V. i have verified all of the R values and solder joints surrounding Q11 on the main pcb-everything looks right. i notice that both of these "error points" connect to the meter board; maybe something is wrong there? i removed R77 cause i have the rotary pot-should i have something there instead? if i disconnect the harness at the meter board, i get all the same readings. also, with Q11 removed, my voltages there look like: D=18V S=-7V G=-7V.

 

[Echo North]

<Setting it to 9 is WAY high.  Maybe there is a larger issue?> Agreed!

<Are you passing signal?>  Yes

<If you measure the output in bypass and then hit GR are you seeing reduction on the output?> Yes. With .775VAC 1kHz tone (0dBu) on input, meter reads 0 on +4 setting, I'm getting 1.223VAC (+4dBu) on output with GR bypassed. With GR engaged,  I get .410VAC, which is -5.53dBu, so about -9.5dB gain reduction on output.

<I wonder if there is an issue in the GR amp itself.> Checked all resistors, even lifted one leg and measured each. All are correct.  Additionally, we checked the ratio board resistors too, all are correct.

<Double check all of the wiring> Will do that next.

<check the voltages in the GR amp.> Did that. Voltages are pretty close, but not exact.

Q7 - 14.75, 4.47, 3.92
Q8 - 14.2
Q9 - 16.94, 3.39, 2.83
Q10 - 16.37

Also replaced all four transistors with HFE tested good parts, just to rule that out. In fact, I've confirmed tonight that every resistor and cap on the main PCB is correct.

In the signal preamp, all voltages were perfect except 11.59 on Q3 (should be 12.58) and 11V out from Q14 (should be 12V).


<Let's get this sorted!  > I'm ready!!!

Check you Pad 21/22 readings.  Read through a few pages here with Steve_H and I for reference.

http://groupdiy.com/index.php?topic=29981.msg614909#msg614909

 

[babaorum]

Hello,

Could you help me, I purchased a rotary switch but One pole and 12 positions.
Is it ok for the mnat's ratio board of the 1176 rev D (rotary version because stereo project)

Here that I have ...  ???

Thanks

Regards

 

[babaorum]

ok, the two holes mean that it's a 2 poles (a 6 positions is enough for 5 real positions) ...  :-\ so I have to change my switch for 2 poles.

And for the GR off / GR / +4 what is required ? a simple pole with 6 position ?

Thanks for help,

baba

 

[AusTex64]

<Check you Pad 21/22 readings.  Read through a few pages here with Steve_H and I for reference.

http://groupdiy.com/index.php?topic=29981.msg614909#msg614909>


Checked pads 21/22, I see the changes tracking as I switch the ratio buttons from 20 to 4. Also checked wiring, all is correct.

Turns out I am a moron. I was not zeroing out the meter before finishing the GR meter cal procedure. I am both happy and humiliated, as the GR meter is working just fine now.  Doh!

When you refer to 0dbm/0.775VAC test tones, is this measured at the output of the oscillator (no load), or at the input jack of the unit (under load of the input transformer)? If I measure inside the unit I have to jack up the oscillator output a bit to measure 0.775VAC on the input jack. But if I do this, the input gain control seems to behave more like I would expect as relates to how much compression I can get. At 12 o'clock I can get -10db compression at 20:1, no problem. No more need to turn it almost all the way up.

Speaking of the input transformer, if I move the mu metal case, it shorts out the input. Should I put a bit of silicone between it and the PCB to hold it still? Should I be concerned?

Time to try thing thing with audio and test tones next to my bluestripe. Will know for sure then, but I have this nagging feeling this Rev D doesn't have as much gain.

Thanks for your support Mike! You bring the love to DIY...

 

[Echo North]

<Check you Pad 21/22 readings.  Read through a few pages here with Steve_H and I for reference.

http://groupdiy.com/index.php?topic=29981.msg614909#msg614909>


Checked pads 21/22, I see the changes tracking as I switch the ratio buttons from 20 to 4. Also checked wiring, all is correct.

Turns out I am a moron. I was not zeroing out the meter before finishing the GR meter cal procedure. I am both happy and humiliated, as the GR meter is working just fine now.  Doh!

When you refer to 0dbm/0.775VAC test tones, is this measured at the output of the oscillator (no load), or at the input jack of the unit (under load of the input transformer)? If I measure inside the unit I have to jack up the oscillator output a bit to measure 0.775VAC on the input jack. But if I do this, the input gain control seems to behave more like I would expect as relates to how much compression I can get. At 12 o'clock I can get -10db compression at 20:1, no problem. No more need to turn it almost all the way up.

Speaking of the input transformer, if I move the mu metal case, it shorts out the input. Should I put a bit of silicone between it and the PCB to hold it still? Should I be concerned?

Time to try thing thing with audio and test tones next to my bluestripe. Will know for sure then, but I have this nagging feeling this Rev D doesn't have as much gain.

Thanks for your support Mike! You bring the love to DIY...

Great!

Yes you want to feed the circuit 0.775 dBu under load.  Because of the 600Ω line input impedance you'll get some impedance loss.  You may actually need to feed 2V to see 0.775 across pin 2 and 3 of the input.

May be a bad input or loose connection.  You could try a little silicone.  Let me know if it gives you issues.

The D has 5 or 6 dB less gain than the A by design.

Mike

 

[rjd2rjd2]

thanks again for everyone who is able to help out on this site. 2 questions:

1-the 8.2K resistor on the GR meter PCB: if i'm using the rotary attack pot on/off version, should i have this R in place? if not, do i substitute anything, or just leave it open?

2-R79: i am seeing 30V on the "upstream" side of this, but only 2.1V on the "downstream" side. both sides of R74, both sides of R67, and the D pin of Q11 all read 2.1V. if i remove Q11 from it's socket, the D pin jumps to about 12V. Where should I be looking? (I have checked all of my R values in the GR meter driver section.)

thanks again for any help.

 

[mattvon]

Hi all, just finished up wiring a Rev D build and I'm stuck at the first calibration step.  I've tried both the mnats method as outlined in the video and the Hairball method.

The issue is that I'm not able to get the voltage to ever approach the base levels.  When using the Hairball method for Q bias, if I set the input pot at "24" and slowly increase the output pot from full CCW, turning CW, I get a peak of just barely over 1.0 VAC and then it diminishes back to near 0 VAC at full CW.  I thought I had the pot wired incorrectly, but it appears correct.

The mnats method is equally unsuccessful.  With the input pot all the way up, I'm able to sweep the VU needle up to -2 once the output pot reaches "24" and then it drops back again to -20.

Thoughts?  Bad pot?  Dumb newbie mistake?  I have really enjoyed this build and I'm hopeful you nice folks can help me get it sorted out...

Thanks in advance,

Matt