[BUILD] 1176LN Rev D DIY

[tazman]

No.  Mine basically was distorting.  When I strummed the guitar or hit the bass drum, the transient would produce heavy distortion which got worse with increased ratio or input.

 

[dandeurloo]

Way to stick it out and thank God for guys like Mr. Kulka!  Everyone of those little lesson add up.  I'm no genius when it comes to electronics or anything else but I have had a number of genius teach me a few lesson and I am thankful for them.  Glad you got it working.  Hopefully I can get mine doing something soon.  More parts showed up today.

 

[tazman]

I look at it this way.  I did all I knew to do.  I wanted the comp to work and having someone with more experience figure it out provided me with:

a.) a working comp
b.) a comp that works exactly how it should (so I know it's working as an 1176 should be and I can use it for reference on future builds)
c.) I learned new solutions to problems or better, new approaches.


Cheers,

Rob

 

[TijuanaKez]

Hey guys,

I made a new thread for this by accident, hopefully a mod will find and delete...

I built an 1176 revD with the hairball kit and mnats board and it passes audio and compresses but it doesn't sound right.
It has way more gain in the preamp stage when a/b'd with an origional and the g/r stage seems to react somewhat randomly to some signals. It also produces clicking and popping noises with heavy g/r. My UAD plugin version doesn't exibit any of these behaviours (haven't a/b'd the last 2 symptoms that with a real unit though).

Anyways I have double checked all the components with a DMM in circuit and %90 are reading correct. I started pulling the ones that didn't but they were all reading correct values when pulled out of circuit so i stopped as it was making things messy. Best get to the source of the problem.

The first thing I can see is that all voltages test points are reading correct except for the preamp stage which is way out compared to the schematic.

The first and most obvious is the C pin on Q3 is only reading 5V but it should be 12V according to the schematic. Same with Q14 pin E
Following the schematic: 30V -> R17(6.8k) -> R14(22k) -> Q3 pin C (12.58V)
I tested R17 and R14 and they are the correct values but testing each side of the resistors along the way I get this
30V -> 30V[R17]23.85V -> 23.85V[R14]5V -> 5V [Q3 pin C]
It would seem something is going wrong at R14 but it reads 22K exactly as it should.

Can someone help me solve this mystery? My electronics knowledge is fairly limited.

Here are some other Readings

      SCHEMATIC              MY UNIT
          C      B      E          C      B      E
Q2  1.75  1.05  0.54      1.5  0.71  0.21
Q3  12.58  --    1.15      5.0  1.5    0.85
Q14    --      --      12.0    30.0  5.0  4.39

And I'm getting exactly 30V and -10V at the test points in the power supply section.

 

[tazman]

Have you corrected R12 as per D Kulka's finding? 

 

[TijuanaKez]

Have you corrected R12 as per D Kulka's finding?

I haven't, it's still 920 ohms. Do you think that could be responsible for the missing 7 voltz at Q3-C and Q14-E ?
It's quite a big difference. I wish I could work out how 7v goes missing between r17 and Q3-C but I'm limited by my poor knowledge of electronics.

How does a 6.8K in series with a 22k resistor bring 30V down to 12V and why is mine bringing it down to 5V instead?
I have a feeling it's more complicated than using ohms law

 

[tazman]

What are you getting on the + side of C4 and at R13?

Could it be a bad solder joint at R17 (you did say that on one side of R17 you get the full 30V, right?)?

 

[TijuanaKez]

What are you getting on the + side of C4 and at R13?

Could it be a bad solder joint at R17 (you did say that on one side of R17 you get the full 30V, right?)?

I'm getting 30V on one side of R17 and 23.87 on the other.
+ side of C4 and R13 are also measuring 23.87V

 

[tazman]

I would look at R17 again.  From what you say, it sounds like something screwy may be happening there.  Unless it's something downstream, but maybe reflow the solder joints at R17.  You did say you tested it and it measured correct, though.

Have you tried lifting the other leg of R17 and measure the voltage there?  Basically 30V in and ?  on the other lifted leg.

 

[Nick-ES]

First of all I want to say hallo to everyone !

I built two Gyraf 1176 (last gyraf Rev.  aprox 5 years ago) and they worked troublefree
till 1 week ago.
I decided to retrofit them with with the Hairball Audio Stereo Link Kit.

After all wiring was done  with the stereo link kit I mounted the two LN1176 back to the rack
and fired them up. Everything worked fine. Tested them in Mono Mode and everything was ok !

Than onnected the TRS Cable and linked them and put the switch to stereo position - everything worked ok !

I tested them for an hour and everthing was ok in Stereo Mode .

Than I decided to switch one unit back to Mono Mode (while it was switched on and audio was passing thru both)
There the ACCIDENT happened and in the moment I switched to Mono the unit stopped passing Audio and the
Gain reduction Meter went to 0
Now this unit does not work in Mono mode anymore and also does not pass audio in Stereo Mode.

Where can I start to search for the Error ?

Any help would be highly welcome as I loved the both units.

 

[TijuanaKez]

I would look at R17 again.  From what you say, it sounds like something screwy may be happening there.  Unless it's something downstream, but maybe reflow the solder joints at R17.  You did say you tested it and it measured correct, though.

Have you tried lifting the other leg of R17 and measure the voltage there?  Basically 30V in and ?  on the other lifted leg.

Retouched all the solder points in the preamp section but nothing changes. I lifted the non 30V side of R17 and it tests 6.8K exactly out of circuit. But I testes voltages and it's 29.87V on the 30V side and 29.82 on the lifted leg. Can that be right?

 

[tazman]

It doesn't sound right, I hope someone else chimes in too.

If you have a spare resistor I would replace it. 

 

[Mixmaster-Nate]

Hi Y'all, I made a new thread for the Mnats 1176 Rev-D before I found this one...

Anyway, copied it here again - I'm new, my first post and a very amatuer DIY'er.

I've built an Mnats Rev D 1176, no worries building the unit so far.  I've got one remaining component to fit and I'm wondering if anyone can help with a a component substitute.

C1 in the signal preamp section; BOM lists it as a    WIMA Polyester Film Capacitors 100V 1uF 5% (PN; MKS2D041001K00JSSD)

I've had some on order for 3 months with Mouser, and it was supposed to ship 20th July, but it has been back ordered again for the third time to October 

I can get the same WIMA component but with a 10% tolerance, will this make much difference to the operation considering it's in the pre-amp section??

Also - can any one suggest another manufacturer of a similar component that would suffice??  I can't wait until October for mouser only to be let down again...

Appreciated in advance 

 

[s2udio]

I can get the same WIMA component but with a 10% tolerance, will this make much difference to the operation considering it's in the pre-amp section??

Nah,thats fine, sling it in ,any cap of similar type/spec will do.

 

[Mixmaster-Nate]

Thanks, I'll give it a go 

 

[canidoit]

Anyone know if there is the distortion adjustment video or tutorial out for this unit yet?

 

[mnats]

Anyone know if there is the distortion adjustment video or tutorial out for this unit yet?

I haven't found time to complete the planned video for my site yet but the complete procedure is outlined in the original service manual in section 5.3.5 along with some additional information that has been added to that document under the heading "1176LN Limiter Tests".

 

[Hyder]

Hello, First time poster so I hope I am doing this correct. I am Building a REV D and the BOM calls for a .022/100/5 Wima film cap located on the attack pot (C27).
Well Mouser sent me a.022/250/10 Wima Polypropylene Film Cap instead.
Is this a problem? All the pics. I see it looks like a ceramic cap or something.
Thanks,
Chuck

 

[Hank Dussen]

Hello, First time poster so I hope I am doing this correct. I am Building a REV D and the BOM calls for a .022/100/5 Wima film cap located on the attack pot (C27).
Well Mouser sent me a.022/250/10 Wima Polypropylene Film Cap instead.
Is this a problem? All the pics. I see it looks like a ceramic cap or something.
Thanks,
Chuck

No problem.
Capacitance is the same. Yours has a higher voltage rating and 10% margin instead of 5%.

 

[TijuanaKez]

I checked all the resistors in the preamp section by lifting one leg from the board if they didn't measure up in circuit. Everything is as it should be but I still have around 5V on Q3-C and Q14-B and Q14-E, all places where I should be getting 12V. So I decided to start lifting the 2N3391's. I pulled q14 and now Q3-C (and Q14-B solder point) read 12V is they should. Could this mean Q14 is faulty or more likely something downstream from Q14-E? I wish I knew enough about transistors to work it out.