[BUILD] 1176LN Rev D DIY

[weiss]

feed a 0dBu 1K signal directly into the meter terminals.  Does the needle react?

jup. straight to the right

 

[John Peacock]

I'm dusting off this old project...  I purchased the original Mnats rev D board back in 2007.  My board is stuffed and I am partially through hooking up the wires in a Hairball case, which has brought me to a few questions.

1. On the original board there is no ground terminal next to pad 7, as shown on the current hook-up instructions provided by Mnats and Hairball Audio.  I have found some old connection guides that suggest not bothering to connect the shield to ground from the main wire attached to pad 7.  Another guide suggests connecting the shield from the wire at pad 7 to the shield/ground from the wire attached to pad 22.  However, I would think connecting it to the non-connected shield from the input transformer may be easier (as it's closer), if that would work.  Or is there any real trade-off to leaving the pad 7 shield not connected to ground?

2. I am using the Cinemag CM-96731 output transformer.  As stated on Mnats guide about halfway down the following link in the section marked "Output transformer options:"
http://mnats.net/1176_revision_d.html
the output of the transformer can be terminated into a 619ohm resistor.  Where exactly do I place the resistor in terms of the circuit (between ? and ?).  Also, I read that some folks put this resistor on a switch as mentioned in the second to last post in the following link:
http://groupdiy.com/index.php?topic=18209.msg212586;topicseen#msg212586
How exactly can I wire the resistor on a switch.  Meaning, what kind of toggle switch do I need to buy (number of poles?, etc.), and any specifics on the wiring of the switch/resistor would be greatly appreciated.

3. Finally, when I started this project there was no Hairball Audio to make this process, especially the sourcing, much easier.  I bought expensive push-button assemblies directly from UA.  Mike at Hairball has a post here:
http://groupdiy.com/index.php?topic=26998.msg326843#msg326843
where he very clearly explains the connections from the UA ratio board.  He attempts to explain the meter board hookup in the next few posts, but I don't follow.  There are 7 terminals on the UA meter board rather than the 6 found on every diagram I can find (new or old) from Hairball's push-button boards or those old green ones from Mnats (I actually have a set of those, too).  The 7th is for +8 metering?  If this is the case, what does the +8 button do on the modern Hairball/Mnats units?  If someone is able to refer me to a diagram or simply tell me which connections to make from the UA meter board to the Mnats board, that would be great.  Or would I be better off biting the bullet and just buying new meter boards and push-button assemblies from Hairball to make it easier to follow the current wiring diagrams?  Any links, diagrams, insight, etc. would be greatly appreciated.

Thank you!

Just a quick bump to my questions since the thread has rounded another page.  Feel free to pick just one to answer.  Thanks again!

 

[Winetree]

On a Rev. A build, can I use a .01uf Wima Poly Film Cap on the attack pot,
instead of a .015 cap?

 

[ericfergus]

Audible tones can happen when the output is loud enough.

No Compression, but passing signal:

Something is wrong with your side chain.  Things that can cause this:

- Improper QBias adjustment.
- Component error on the Ratio PCB
- Component error on the Attack/Release Pot
- Component error on the side chain section of the PCB
- Wiring between all of those parts.

After checking all of that troubleshoot.

Troubleshooting:
Feed a 1K 0dB signal into the compressor.  In/Out/Att/Rel all set half way. Confirm that you see 0.775 VAC between input pin 2 and 3.

Post your AC voltage between pad 22 and ground for:
20:1 -
12:1 -
8:1 -
4:1 -

Post your DC voltage between pad 21 and ground for:
20:1 -
12:1 -
8:1 -
4:1 -

Post your DC voltage between pad 19 and ground for:
20:1 -
12:1 -
8:1 -
4:1 -

Mike

Hello!  This is my first post here.  I have built a Rev D and it is passing signal.  I do not appear to have any compression through and although the Q bias and Discrete Meter Circuit/Null Adjust seem to calibrate fine, I get no compression when following the "Gain Reduction Meter Tracking Adjustment" steps.  Turing on/off the attack does nothing.

If done my best to check everything.  Connections look fine.  I double checked all resistor codes and cap value stencils.  I haven't found a short.  I also checked the voltage values of all transistors to the MNATS troubleshooting schematic.  Although not perfectly the same, all were close and were proportional between pins.

I did check the HFE on a pile of 708s when stuffing the board and they are closely matched.  Although I purchased a complete kit, I failed to check the HFEs when first stuffing the board, so I purchased a bunch of 708s after the fact and made a matched pair.  If I recall, they measured around 320.

As suggested in Mike's post several months ago, I took the following measurements.

Thanks to anyone who is willing to help!

Eric


Post your AC voltage between pad 22 and ground for:
20:1 13.9mv
12:1 12.5mv
8:1 11.5mv
4:1 7.4mv

Post your DC voltage between pad 21 and ground for:
20:1 -9.69v
12:1 -1.09v
8:1 -1.088v
4:1 -1.089v

Post your DC voltage between pad 19 and ground for:
20:1 -.872v
12:1 -.872v
8:1 -.872v
4:1 -.872v

 

[weiss]

anyone?

 

[leitrim_lad]

Hi there, im wondering if someone can help me..

I posted a few messages on page 211 in relation to problems i was having with the calibration. I havent been able to resolve this since.

My output knob when i turn it it causing a really strange noise. I cannot complete the calibration properly. When i add a 1khz 0db tone and follow calibration instructions the most i can get my vu meter to increase to is -10.. Iv included a video to show the issue. I set my ratio to 20 meter to +4, attack to all the way off and release to clockwise position.. I also have  q bias completely off.. Used a meter to make sure of this.. Something i noticed thought is when i turn the q bias half way its not showing 1 km both ways.. This is when i have it connected to the board.. Is this normal?

any help would be really really appreciated as im really beginning to pull my hair out over this and i havent got much hair left!!! ;-)

Thanks in advance..

link to video:

https://www.youtube.com/watch?v=V3AHr7PCewg&feature=youtu.be

 

[leitrim_lad]

i cant seem to get a reading at all for the 1st calibration step.. I get set 0.775 on the between pin 2 and 3 on the xlr lead coming from the tone output.. when i connect it to the input xlr on the compressor and read between pin 2 and 3 at the back of the xlr im not getting the 0.775 v.. is this normal?

Plus when i read between 2 and 3 on the output xlr im not getting anything near the 2.75vac..

Any help would be great..

Thanks

 

[dbonin]

i cant seem to get a reading at all for the 1st calibration step.. I get set 0.775 on the between pin 2 and 3 on the xlr lead coming from the tone output.. when i connect it to the input xlr on the compressor and read between pin 2 and 3 at the back of the xlr im not getting the 0.775 v.. is this normal?

Plus when i read between 2 and 3 on the output xlr im not getting anything near the 2.75vac..

Any help would be great..

Thanks

check out this post - read at the bottom about the scratchy output - check C7 for polarity.
http://groupdiy.com/index.php?topic=20058.msg693250#msg693250

 

[leitrim_lad]

Hey thanks for that.. i checked c7 and all the others and they all seem ok.. ive attached some pics of the board.. maybe someone might spot something really obvious im missing..

thanks

 

[dbonin]

Hey thanks for that.. i checked c7 and all the others and they all seem ok.. ive attached some pics of the board.. maybe someone might spot something really obvious im missing..

thanks

c7 is in backwards mate

 

[leitrim_lad]

c7 is in backwards mate
[/quote]

Hey Thanks for that don.. I changed C7 and scratchy output has gone. I went through the 3 calibrations as u described in your youtube videos.. Thought everything was good, got through all the calibrations and everything seemed ok but the unit is not compressing.. One thing i did notice is that in calibration step 3 i had to have my input knob for lower then you had yours set to get the 0dB to -10dB.. I seem to have to drive the input knob like mad when a signal is going through the unit. If i put the compressor or ratio 4/8/12 the needle doesnt move at all.. When i put it on ratio 20 the needle moves up to max -3 db and thats with the input  knob up fully.. Would you have any other ideas or advice?

Thanks a million..

 

[leitrim_lad]

Something i did notice is my voltages on Q8 seemed high.. I was getting 24v in the centre.. Is this normal?

 

[leitrim_lad]

Doubled checked everything again today.. went through the 3 calibrations again and everything seemed to calibrate ok but when i put something through to compress im not getting any compression.. In ratio 4 and 8 in GR mode the meter doesnt even move. At ratio 12 and 20 the meter moves slightly but the signal is not being compressed.. Would anyone have any idea of what i might be doing wrong?

Thanks a million

 

[leitrim_lad]

I think i can see the problem.. Someone ight tell me if this is correct or not.. I done what was done in this comment to check voltage drop on output when different ratio of compression is enabled

http://groupdiy.com/index.php?topic=20058.4020

On ratio 4 and 8 and 20 im getting no drop, on 12 im getting a very slight drop..

I take it this isnt normal?

 

[junkface]

having a problem on step three of the calibration and I thought I'd see if anybody had an idea off the top of their head. Steps one and two went easily and I double checked my work JIC. I'm getting the proper voltages in and out for 0db and -10db with and without compression. my problem is the R44 trimmer for tracking adjust doesn't seem to be doing much of anything, so I can't get the meter to read -10db in GR mode.
Is this one of those issues where a 5k replacement trimmer would help? Or do I just have a bad R44 that needs to be replaced with another 2k?

thanks for any first impressions. I'm gonna triple check my work now.

 

[Nedrum]

I would like to know what is optimal for C7, C10 and C17. The schematic specifically designates 1uf electrolytics, and there are other 1uf capacitors where electrolytic are not designated (C1), so I'm inclined to go with the electrolytics, but then I saw the following post. Add to that that the PCB doesn't designate polarity for these while it does for the other electrolytics. I have 1uf WIMAs on hand. Would the films in fact be superior? I've read that similar valued electrolytic and film capacitors should not be considered interchangeable (e.g. http://www.apec-conf.org/wp-content/uploads/2013/09/is1.3.2.pdf), so is there a specific reason these capacitors should be electrolytic or does it really matter?

I assume that you checked all resistors and capacitor values...
Transistors:
2n3708 are well placed
Did you use 2n3391 or equivalent?
Did you placed in proper order all bipolar transistors?
What FET did you use? If 2n5457 - both are wrong placed.
Yes, C7 is wrong placed. Also check tantal capacitors polarization, cause i don't see them from this angle.
For C7, C10, C17 is better to use film caps.

 

[ln76d]

I would like to know what is optimal for C7, C10 and C17. The schematic specifically designates 1uf electrolytics, and there are other 1uf capacitors where electrolytic are not designated (C1), so I'm inclined to go with the electrolytics, but then I saw the following post. Add to that that the PCB doesn't designate polarity for these while it does for the other electrolytics. I have 1uf WIMAs on hand. Would the films in fact be superior? I've read that similar valued electrolytic and film capacitors should not be considered interchangeable (e.g. http://www.apec-conf.org/wp-content/uploads/2013/09/is1.3.2.pdf), so is there a specific reason these capacitors should be electrolytic or does it really matter?

If am not wrong, 1176 original  were made with electroytics in place of C7,C10,C17.  Referring to mnats manual (BOM especially), there's  "CAP ELEC OR FILM" description - so that means you can use both types. Capacitor types are interchangeable only in some cases, it depends from the job in the circuit.  If you  can use a film cap, use film cap - that's always better - more stable, not aging etc.

 

[Nedrum]

Thanks ln76d for the confirmation and noting the info on mnats' BOM. I'm going to go ahead and use the WIMAs.

 

[ericfergus]

Audible tones can happen when the output is loud enough.

No Compression, but passing signal:

Something is wrong with your side chain.  Things that can cause this:

- Improper QBias adjustment.
- Component error on the Ratio PCB
- Component error on the Attack/Release Pot
- Component error on the side chain section of the PCB
- Wiring between all of those parts.

After checking all of that troubleshoot.

Troubleshooting:
Feed a 1K 0dB signal into the compressor.  In/Out/Att/Rel all set half way. Confirm that you see 0.775 VAC between input pin 2 and 3.

Post your AC voltage between pad 22 and ground for:
20:1 -
12:1 -
8:1 -
4:1 -

Post your DC voltage between pad 21 and ground for:
20:1 -
12:1 -
8:1 -
4:1 -

Post your DC voltage between pad 19 and ground for:
20:1 -
12:1 -
8:1 -
4:1 -

Mike

Hello!  This is my first post here.  I have built a Rev D and it is passing signal.  I do not appear to have any compression through and although the Q bias and Discrete Meter Circuit/Null Adjust seem to calibrate fine, I get no compression when following the "Gain Reduction Meter Tracking Adjustment" steps.  Turing on/off the attack does nothing.

If done my best to check everything.  Connections look fine.  I double checked all resistor codes and cap value stencils.  I haven't found a short.  I also checked the voltage values of all transistors to the MNATS troubleshooting schematic.  Although not perfectly the same, all were close and were proportional between pins.

I did check the HFE on a pile of 708s when stuffing the board and they are closely matched.  Although I purchased a complete kit, I failed to check the HFEs when first stuffing the board, so I purchased a bunch of 708s after the fact and made a matched pair.  If I recall, they measured around 320.

As suggested in Mike's post several months ago, I took the following measurements.

Thanks to anyone who is willing to help!

Eric


Post your AC voltage between pad 22 and ground for:
20:1 13.9mv
12:1 12.5mv
8:1 11.5mv
4:1 7.4mv

Post your DC voltage between pad 21 and ground for:
20:1 -9.69v
12:1 -1.09v
8:1 -1.088v
4:1 -1.089v

Post your DC voltage between pad 19 and ground for:
20:1 -.872v
12:1 -.872v
8:1 -.872v
4:1 -.872v

Hello everyone!  I posted the above over a month ago but received no response.  In the meantime my poor 1176 is gathering dust without compression.  Is there anyone that  might be able to point me in a new direction of troubleshooting?  Thanks aplenty for your time!

E

 

[Echo North]

I also noticed that the ratios seem odd. I get the most compression when 4:1 is engaged.

That's normal.  The threshold is higher at lower ratio's.  There is more GR on the meter, but the actual RATIO is lower.

You need to triple check you wiring, calibration, and components.

Check your voltages against the schematic w/ voltages on the MNATS site.