PLEASE HELP!!!: 1176 BUILD....

[FatherSonteam]

Hello techno wizards! 
Me and my Dad have been working on an MNats 1176 rev D build for 6 months now. We have exhausted all of our friends who do electronics but we need some experts like you guys to help! My Dad worked for Sharp back in the day but hasn't done built anything for years but now as he's semi retired decided to build me this after much nagging. We did put a post on another forum explaining our issues but got no love, no idea why. I've uploaded a videos showing you our build which I'm really excited to use in my studio (peak Studios) in Bradford, UK. Also below is a load of pictures I've taken to show the wiring and board. There's no dry joints but its still not playing. The unit powers on fine and signal passes but the compressor doesn't kick in and the needle doesn't go to zero.
Any ideas where we've gone wrong?

http://youtu.be/0LsW2m-yT3k

Any Ideas?

 

[kato]

Hello fellow Hoosier! 

Very cool of your dad to help with this. I wish I had anywhere near that kind of rapport with my dad, so count that blessing.

Your wiring job looks very neat so I'd guess the hang up is something weird and hard to predict. So we'll start with the obvious, and please pardon the dumb questions that follow...

My first thought: passing signal but not compressing means it's not calibrated. Have you gone through the calibration procedures?  (Like I said, dumb questions, but I gotta ask.) As detailed on this page, specific to the rev. D:
http://mnats.net/1176_revision_d.html

 

[gemini86]

First thing's first, calibrate as Kato said. If things aren't grooving after that, then let's see all the DC voltages at each transistor in the side chain amps. (may as well check the whole thing)

This will start to help you eliminate sections of the circuit so you can focus your attention to problem areas.

 

[FatherSonteam]

Thanks gemini86 and kato for your replies! We did try the procedure but basically the needle never moves so we could turn the screw all the way both ways but that thing won't move from hard left. We tried every part but it still didn't budge. Ill get my dad to go over the resister values this weekend and well get back to you. Also is there a way of checking the tiny blue trimmers on the board actually work? They all feel different to me. Some screws you can see moving up and down and others stay the same level.

 

[gemini86]

I started out using those blue multi turn trimmers, but I ran into the same problems as you have, not knowing where in the world the wiper is. I swapped them out for single turn trimmers. It takes some finesse to dial things in just right, but it's much easier to see what's going on.

If you can't complete the calibration, take voltage measurements at each transistor, print out a schematic and write it all down at the corresponding points so you can get a good visual. Post the results in the official 1176 build thread here: http://www.groupdiy.com/dynamic-processors/(build)-1176ln-rev-d-diy/?topicseen so that all of the information is in one thread, that way others can find it easily and can learn from your mistakes.

 

[fpliuzzi]

Hello,
Maybe my eyes are playing tricks on me, but is there a reason that the 2K trimpot R71 appears to be missing from your PCB? (normally located close to Q11). It looks like R71 is the "0" set trimmer for the meter driver circuit.

Regards,
Frank

 

[berkleystudios]

Hello,
Maybe my eyes are playing tricks on me, but is there a reason that the 2K trimpot R71 appears to be missing from your PCB? (normally located close to Q11). It looks like R71 is the "0" set trimmer for the meter driver circuit.

Regards,
Frank

he has the pot wired to the bottom of the board.


is there a specific reason yo did that? why did you not use the dedicated though holes?

 

[gemini86]

on the original 1176, the zero trim pot is accessible from the front panel through a small hole.

 

[berkleystudios]

on the original 1176, the zero trim pot is accessible from the front panel through a small hole.

yes i understand that. he just connected it to other solder joints under the pcb, on mnats board there are dedicated through holes for the wiring of the zero trip pot, just curious as to why he id not use them...

 

[gemini86]

I gotcha...

probably just to hide the wires underneath.

 

[FatherSonteam]

I gotcha...

probably just to hide the wires underneath.

Yea. I think it was just to hide the wires. We'll go over those connection points on monday just to make sure.

If you can't complete the calibration, take voltage measurements at each transistor, print out a schematic and write it all down at the corresponding points so you can get a good visual. Post the results in the official 1176 build thread here: http://www.groupdiy.com/dynamic-processors/(build)-1176ln-rev-d-diy/?topicseen so that all of the information is in one thread, that way others can find it easily and can learn from your mistakes.

My Dads away this weekend but should be back later today and can do a few replies then. I might swap out those multi turn trimmers for the single turn ones. I don't like not seeing how it changes as I turn it. In my head I'm thinking this thing could be threaded and spinning but doing nothing for all I know. Obviously if its working you'd know, but our unit isn't. ;-)
Thanks for all the help guys! Very excited to get this beast working!
Cheers!

 

[FatherSonteam]

Hi Fellas!!! Sorry its taken so long to get back with these its been a busy few weeks!!

So we've done a full layout of the readings. The readings seem to go pear-shaped at the Signal Pre-Amp stage, then really pear shaped in the Meter Driver circuit, which sort of all ties together. Any ideas why this is happening?

Q No. E B C
10 16.3 15.7 29.7
9        2.8 3.4 15.5
8 14.1 14.5 29.7
7   3.9 4.2 14.5
6   2.6 2.1 27.2
5   2.6 2.9 24.6
4   0.4 0.9 4.7
14   4.1 4.7 29.7
3   0.8 1.4 4.7
2   0.2 0.5 1.4
12   1.9 2.5 1.9
13   1.6 -0.4 0.5

G D S
1 0.6 0 0
11 2 2.9 2.5


voltages taken with the unit 'warmed up',
with no signal input applied, and un-callibrated as we haven't got the needle to move to zero yet.

Any help would be really appreciated!!

 

[jeff s.]

Hi,
I am having the same exact issue with audio going in and out but no trim pot adjustments functioning. after going over mine a few times to make sure everything was correct, I noticed my trim pots were soldered in differently than pictures I see of other peoples functioning units. In the photos (of the functioning units) pin two of all the trim pots seem to be one off from the other two pins going towards the drawn screw. Mine and the ones pictured by FatherSonTeam are all lined on the three top holes of the trim pot on the pcb. Could this be what the problem is? I want to make sure before I order new trim pots and pull these one out of the board.
Sorry if my wording and terminology is off and thanks in advance for any help somebody can give me.

 

[berkleystudios]

Hi,
I am having the same exact issue with audio going in and out but no trim pot adjustments functioning. after going over mine a few times to make sure everything was correct, I noticed my trim pots were soldered in differently than pictures I see of other peoples functioning units. In the photos (of the functioning units) pin two of all the trim pots seem to be one off from the other two pins going towards the drawn screw. Mine and the ones pictured by FatherSonTeam are all lined on the three top holes of the trim pot on the pcb. Could this be what the problem is? I want to make sure before I order new trim pots and pull these one out of the board.
Sorry if my wording and terminology is off and thanks in advance for any help somebody can give me.

 

[Hasse]

Hi there.
I've been following this thred for a while and find it really interesting.
I love to solve problems even though I don't completely undersand what I'm doing... :-\

I had some similar issues whith mine. Even though my meter was moving and I could calibrate it, it didn't work properly, but I was thinking: "well, close enough for rock'n roll".
I changed my trimpots to these:

It works now and is REALLY close for rock'n roll! The multiturn trimpots did'n twork... The viper did not move at all.
But your unit seem to have some other issue about the meter. Does it move at all? Not even when pushing the +4 button and adding a signal? If so, there must be something wrong with the meter.
If it moves to measure output but not the GR, check the wiring on the pushbutton panel or measure the connections between the meter and the Null adj pot / meter and the 3,6k resistor when the GR button is pushed. To be sure that the TL071 is working properly, you have to check the Tracking multiturn pot. (That was the pot that did'nt work for me). But first of all(!?) you have to check the Q-bias adj. pot. This is, due to the Mnats calibration guide, the most important adjustment on the unit.
This makes the transistors work in the right conditions. If that don't work/is set right, nothing work properly.

This may be obvious and you have probably already done all this but it worked for me and hopefully it might help you or someone else that are reading this thread.
Please be patient with my spelling and grammar  :-\

 

[jeff s.]

Hi there.
I've been following this thred for a while and find it really interesting.
I love to solve problems even though I don't completely undersand what I'm doing... :-\

I had some similar issues whith mine. Even though my meter was moving and I could calibrate it, it didn't work properly, but I was thinking: "well, close enough for rock'n roll".
I changed my trimpots to these:

It works now and is REALLY close for rock'n roll! The multiturn trimpots did'n twork... The viper did not move at all.
But your unit seem to have some other issue about the meter. Does it move at all? Not even when pushing the +4 button and adding a signal? If so, there must be something wrong with the meter.

If it moves to measure output but not the GR, check the wiring on the pushbutton panel or measure the connections between the meter and the Null adj pot / meter and the 3,6k resistor when the GR button is pushed. To be sure that the TL071 is working properly, you have to check the Tracking multiturn pot. (That was the pot that did'nt work for me). But first of all(!?) you have to check the Q-bias adj. pot. This is, due to the Mnats calibration guide, the most important adjustment on the unit.
This makes the transistors work in the right conditions. If that don't work/is set right, nothing work properly.

This may be obvious and you have probably already done all this but it worked for me and hopefully it might help you or someone else that are reading this thread.
Please be patient with my spelling and grammar  :-\

Thanks Hasse,
As for me, on both my units the in and out pots are working fine. Its only the tim pots that are not functioning. I checked the wiring like you said and both seem to be set up correctly. I will look into how to measure the meter connections like suggested also. I am pretty new to trouble shooting like this so it might take me a bit to figure out how to do it. I notice on the trim pot you suggested that the pins are not lined up like the blue trim pots I have. looking at say R44 there are 6 places to place the trim pot that forms a "T". Mine and the ones ones pictured on this thread are on the top three of the "T" I see pictures of other units where it looks like they are wired differently and the trim pot you show seems like it has to be wired differently. Do you know if this makes a difference at all?
Thanks so much for your response.
Jeff

 

[Hasse]

The "leg" on the "T" is only for the option of 4 different kind of trimpots. The "upper" left/right holes are allways used, regardless of what kind of trim you use. The "Leg" has four holes for the option of having a trim like pictured for example. These holes are the same, only different places for the viper on the pot. The viper is the middle pin that moves from left to right inside the pot.
You can check it (the null adj for example. NOT the "0" set on the front) without turning the unit on. Just connect your multimeter somewhere on the board where it connects the viper (on one of the free holes that connects to the viper for ex) and the other lead to one of the other pins of the trim. Or on the nearest resistor connected to them. 1k or 8,2k resistors. Turn the pot on the trim and look for any changes on the multimeter (that is set to measure 0-100 ohms). From one side to another, all the way. In one direcion you should hear the multimeter sound with a beep, that means shortcut, or "connected".
Don't connect the cord to the wall.
That way you can check if it works at all.
If you are unsure, take it away and measure it alone without any connection to the board.
That is the most secure and accurate methode to check any component. Just take some time.

 

[jeff s.]

Thanks Hasse, You have been a tone of help. I checked out the trim pots and noticed some functioned and some did not. How could it be possible that I have this many bad trim pots? could I have over heated them when I was soldering them in the board. On one unit the Q bias trim pot is functioning fine but doesn't work in calibration. R44 and R86 are not functioning on that same unit. Do all the trim pots need to be functioning properly in order to get the Q bias to actually work? Do you have a  model number for those trim pots you recommended? I am going to try to order them tomorrow and see if this makes a difference at all.
Thanks again for all your help on this.

 

[Hasse]

Glad to hear that you did manage to find the components that did'nt work.
I don't know where you live but Mouser has a lot of different trimpots.
This might be what you're looking for: http://se.mouser.com/ProductDetail/Bourns/3319P-1-202/?qs=sGAEpiMZZMtC25l1F4XBU2VDyyiMO6RA%252bt4a1tLcKQw%3d
It's a Bourns trimpot 2kOhms.

 

[SaMpLeGoD]

Hey, just go for the multiturn trimmers, except for R71 (0 set) if you want, because it's nice to get it available at the front panel to adjust anytime you need.
Just a few questions:
Wich transistors did you used? be carefull if you did not used 2N3707... if you used 2N5088's mind the extra pad available, they have not the same pinout!!!
If you used the 2N3707, some of them need to be above 500 HFE If I'm not mistaken... really don't remind how much HFE needed.
Did you move the jumper to the right place when calibrating? if not, or no jumper, you have the GR always out of the circuit!

When GR is off pad 22 is connected to ground... check if you have always this situation... maybe you have a wiring problem on the attack's pot switch! by the way, I noticed that your switchable pot is on the release hole! the 25K SPDT switch should be on the attack pot! please check if you don't mess with the attack / release pot's wiring

Here some calibrating videos if you don't saw it yet.

Step one: http://www.youtube.com/watch?v=WuDdVY1R__w

Step two: http://www.youtube.com/watch?v=at82NxrPQzI

Step Three: http://www.youtube.com/watch?v=IOzaWP8ACLs

Hope it helps!
Cheers

Eddie