[BUILD] 1176LN Rev D DIY

[college101]

got it working..the new fuse I put in was bad!  its working now!

 

[dandeurloo]

sweet!  Gotta love cheap and simple!

 

[dandeurloo]

So, just gotta bump again for my issue.  Anyone have any ideas?

 

[TijuanaKez]

Ok I've noted what's happenning on the schematic in the hope the someone with more knowledge of electronics can help me. My original message.....

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.

So my question is, what could be happening to make Q3-C (Q14-B) and Q14-E drop 7 Volts when Q14 is in circuit??

I just got a new bag of 2N3391's so I know Q14 is not blown. I also tested all the resistors in the signal preamp section, and double checked the ones close to Q14 (marked as tested in red on the schematic).

All other voltages marked in the schematic read correct values on my board.

 

[TijuanaKez]

Anyone?

I feel I've narrowed down the problem to small area. I'm sure someone who understands this stuff could take a peek at that schematic and point me in the direction of where my problem lies.

 

[college101]

I would take a gander and say that the most obvious problem is the problem...replace that part and insert a new one, then take measurements again, and report back to us with what you find!!

 

[TijuanaKez]

Which part? The only suspect part was the 2n3391 at Q14 but I tried a fresh one and still the same.

 

[college101]

Im actually having some problems with the Gain reduction meter tracking adjustment..or Video#3 in mnats youtube videos on how to completely calibrate your 1176 ln rev d board...

In the video, when setting the initial controls for the front panel

After I set the input and output to mid position, and make sure that r44 is in the circuit...short 22 to ground(which is essentially turning off the compression via the attack switch-I turn off the compression) apply the 1k tone at .775 dc  ****RIGHT HERE*** in the video, the needle swings out to +3 (in the RED side of the VU) my needle swings all the way to the left...(This has to be wrong, HELP HELP HELP Guys-what do I do?   

Your supposed to adjust the output control to show ZERO VU...but I cant turn my input UP anymore to get it to reach zero vu! it is in between -7 and -5 area in the vu

HELP!

 

[college101]

Which part? The only suspect part was the 2n3391 at Q14 but I tried a fresh one and still the same.

I would start to change out multiple 2n3391 and see if that solves it...this is where troubleshooting comes into play...Sometimes a part is showing a reading because something else is causing it to read that way....

The new part could be bad too...That just happened to me with my fuse...Ordered a brand new one, popped it in, and my 76 wouldn't turn on...went back after Harpo told me to check it again, and it was the fuse..

I would change out all of the 2n3391's...and see if that makes a difference,before that, I would go back and check caps to make sure they are set correctly...and check your connections...If you have over heated a pad, its possible its not making a good conection

 

[college101]

OK... I figured out..for some reason, on my style audio generator, I have to connect my ground to one side of the 600 ohm output...I do that and my needle goes to the right side...

 

[college101]

im almost there..got the +4 settings!!!  now working on the GR settings!!!

 

[college101]

HELP GUYS..new problem...cant get the tracking adjust meter(R44) to adjust the needle, wether GR is on or off!? what to do guys?  I re heated solder joints and re checked the part....it tested fine...


I am also kind of wondering if setting the front panel controls is actually calibrating my unit..I can get it to show 0 and the with compression on..drop to minus ten...BUT now that I have that set, when I re-engage the GR off- the needle does not drop back to zero... Im so confused

 

[college101]

SO GUYS...I have pulled , and found that r44 was bad- replaced it, and now, same thing is happening again, once I go from the +4 meter setting, by calibrating 0 vu with no compression, and -10 with compression-I set to GR, and watch the meter drop back to zero vu- Your supposed to turn on compression and adjust r44 to adjust  the difference to set back to -10..when I switch on the compression while feeding the signal, r44 does nothing....

 

[college101]

OK..so R44 still does not work...Inserted it in place, re solder'd  and nothing...Once I go into GR mode from the VU or +4 setting back into GR mode...U re zero the meter using R71...then turn on the compression, and watch the needle drop to the LEFT from the zero...mine lands around -7 and no amount of turning r44 moves the needle to -10...HELP

I am also noticing a lot of Drifting by the needle....Does anybody else have a lot of movement in their VU meters needle movement?

Comments please...I am going on my third R44 2k trimmer...and now I have to order some more to change it again


Ive seen a few posts from other people where they were using the big pots with wire leads coming from their mnats boards to the pots, they replaced them with the small mini trimmers...Is this my next move to set r44 correctly?  Speak up fellow 76'ers~!!!????

 

[college101]

BUMB anybody got input on this?

 

[canidoit]

From my understanding, the big pot was for the zero adjustment going to the front panel hole. It's been a while since I did the 1176. Have a look at my journey thread and see if theres any useful info regarding callibration.
http://www.groupdiy.com/index.php?topic=34385.0

All the best mate!

OK..so R44 still does not work...Inserted it in place, re solder'd  and nothing...Once I go into GR mode from the VU or +4 setting back into GR mode...U re zero the meter using R71...then turn on the compression, and watch the needle drop to the LEFT from the zero...mine lands around -7 and no amount of turning r44 moves the needle to -10...HELP

I am also noticing a lot of Drifting by the needle....Does anybody else have a lot of movement in their VU meters needle movement?

Comments please...I am going on my third R44 2k trimmer...and now I have to order some more to change it again


Ive seen a few posts from other people where they were using the big pots with wire leads coming from their mnats boards to the pots, they replaced them with the small mini trimmers...Is this my next move to set r44 correctly?  Speak up fellow 76'ers~!!!????

 

[college101]

canidiot...thanks for the info..I have begun reading this...

From what I have recently checked...all of my voltages are correct =just having problems with r44

speak up people...

 

[uzak33]

hi i recently purchased a 1176ln hairball rev d kit with mnats board v2.2.
(input transformer: altran C3837-1, output transformer: 5002)

and got it totally assembled and wired, now i got following problems:

0,770V sinus 1khz on input

output measurements (input pot and output pot fully CW) - 0,3V on blue(pin2) 0V on
red(pin3)

as you see i dont get proper levels (sound is also very very thin and
> output unbalanced)
>
> further measurements with Scope:
>
> wave shows only before input transformer and on GREY output from board
>
> no wave behind input transformer (board sockets) no wave on Q2-Q6.
>
> DC measurements show correct values refering to mnats shematic with typical voltages.
> also resistors should be ok..
>
> Hopefully some has got an idee what could be wrong.

Thanks for any help!!

 

[TijuanaKez]

hi i recently purchased a 1176ln hairball rev d kit with mnats board v2.2.
(input transformer: altran C3837-1, output transformer: 5002)

and got it totally assembled and wired, now i got following problems:

0,770V sinus 1khz on input

output measurements (input pot and output pot fully CW) - 0,3V on blue(pin2) 0V on
red(pin3)

as you see i dont get proper levels (sound is also very very thin and
> output unbalanced)
>
> further measurements with Scope:
>
> wave shows only before input transformer and on GREY output from board
>
> no wave behind input transformer (board sockets) no wave on Q2-Q6.
>
> DC measurements show correct values refering to mnats shematic with typical voltages.
> also resistors should be ok..
>
> Hopefully some has got an idee what could be wrong.

Thanks for any help!!

Double check your connections from the XLR input to input transformer and input transformer to the board. Then double check connections from board to output xlr. I had a similar issue then realised I had the ground and pin 2 swapped at the terminal block that connects directly to the output XLR.

It's the blind leading the blind around here these days it seems ....

 

[uzak33]

i will double check again. but if that is ok, what else could it be..

is it possible that input or output transformers have problems.

best