All things G1176 - the new "repost" thread.

[dissonantstring]

hi synthetic,
you should have it wired like the split secondaries +/- power supply
example. with your center tap (0) and the two other secondary leads giving 24V.
-grant

 

[dissonantstring]

hi synthetic,
is this the power tranny you have: model #266J48?
i got this off the hammond site (48V/24V+24V @ 2A)?

 

[synthetic]

Correct, it's a Hammond 266J48. I have Orange and White connected to the AC input, Brown and black connected to the other AC input leg. Blue and red (1/2 of the secondary) go to the two 24VAC inputs of the board, the other two are not connected. No part of the transformer is connected to ground.

OK, I was measuring from one side to ground each time. If I measure from one leg to the other, I read 26VAC. So pilot error again, I guess. No audio yet, so I'll be spending the day troubleshooting.

Thanks for your help, -jl

 

[dissonantstring]

hi synthetic,
looking at the hammond site - the blue and red are on the same winding.
i've only got a couple of diy stuff under my belt so i'm kinda new at this,
but i believe that you should tie the blue and grey wires of the secondaries together (this will be your center tap 0V to the board) and the yellow and red (one each) go to the 24V connections on the board.
your primaries seem to be connected correctly. just make sure that the AC inlet is grounded via the input XLR 4th lug or chassis.
i tied my center tap connections together and soldered a single lead to it and connected it to my mnats G1176 board. i believe mnats did it the same way as it looks on his webpage pictures. my test points checked out a little under but within voltages. though i'm using the avel lindberg toroidals.
-grant

 

[synthetic]

I get 26VAC from the secondary when I measure from one side to the other. If I measure from one side to ground, I get 13VAC. I assumed that I only want one half of the transformer secondary wired up, since it's a 48V transformer.

I'm not getting the correct voltage at the input to the regulator. I'm seeing 4.5VDC at pin 1 and 3.2VDC at pin 3. (I think it's pin three: on the other side of the regulator from pin 1.) I've checked my solder joints and capacitor orientation. I checked the diodes with a continuity tester and they seem to be working correctly. I get -10VDC at R85, which is correct according to mnat's instructions. Any clues as to what might be my problem?

Thanks again, -jl

 

[gyraf]

JL,

As mentioned, you'll need a transformer with at least 2x24V secondary voltage. Otherwise you won't be able to get the needed +30V.

Jakob E.

 

[synthetic]

I have a 48V/2x24V transformer. I assumed I would only want to use half of this secondary for 24V. Should I be using the entire (48V) secondary and grounding the center?

 

[synthetic]

OK, I get ~30V now, but no audio. I'll troubleshoot some more today.

 

[Mr. Dave]

Hi Everybody,
Should the rotary switches on the Mnats boards be shorting or non shorting?
Thanks,
Dave

 

[gyraf]

dosen't matter much - but non-shorting may be preferable by a small margin..

Jakob E.

 

[Kristian]

Hi
I'm building two 1176 on mnats board. I'm done with the first one but I have some problem.(reversed output Lundahl)
No compression what I can hear. No diffrent sound when I switch bypass and 4+.
Input and output pots are working fine. Sound OK but quiet, maybe 15-20db down.(input and output set at half)

I´ve tried some callibration, but I have chep VU with Ge diode bridge so I have to change 3,6K resistor later on.

I should hear compression? never worked with the real thing, but somethings appers to be wrong.

Kristian

 

[FotisGR]

I has exactly the same problem few days ago. Change the 2 fets.
Must be BF245A or 2n5457.
For VU meters , i used in the past some no cheap but dc vu meters (without diodes for GR metering) that worked excellent for me.

Cheers
fotis

 

[thedug]

I just got the 1176s up and they are doing some funny stuff.

When the input is all the way up the signal drops out.
The attack doesn?t seem to do anything unless the meter isn?t reflecting it. More investigation may be in order.

One unit stops passing signal when the attack is set to slow.

Also, the output knob doesn't really do anything on that unit.

 

[gyraf]

When you turn up input level, GR SHOULD set in heavily at one point. This might be alright.

The attack time goes from fast to damned fast. I'm not sure it would show up on the meters anyway.

But on the second one look for the usual suspects (specially wireing)...

Jakob E.

 

[synthetic]

I got as far on my 1176 to figure out "it's not working" before I went on the road. I've been sitting in hotel rooms every night wishing I could work on the compressor, then I figured out something I could do. I created an image that labels the expected voltage readings (from Gyraf's annotated 1176 schematic) on top of mnat's checkplot. Perhaps this will be useful for someone -- I'm hoping it will save me time this weekend. PM me if you find any errors and I'll try to keep it accurate.

http://home.earthlink.net/~synthetic/1176_revh_checkplot_volts.gif

Cheers. :guinness: :guinness:

 

[Kristian]

No compression what I can hear. No diffrent sound when I switch bypass and 4+.
Input and output pots are working fine. Sound OK but quiet, maybe 15-20db down.(input and output set at half)

I changed FET's but without sucsess. When I pull out Q1 I've got full volume. I guess the gate never opens. Then I saw I had Q15 C=29,6V B=26,4V E=25,9V. I Changed Q14 and Q15. Checked resistor some resistor around that area but I can't find anything wrong exept the voltage on Q15. If anyone has any ide

Kristian

 

[mfdu]

synthetic

that volt plot is a pearler!!!! good on ya, mate.

i've been meaning to trim through this excessively large post and trim out all the facts and details. you've inspired me.

chris.

 

[Kristian]

Very nice synthetic.
I found my problem. Wrong value on R67(38,3k). Still not working rigth. No voltage drop on Q15 B=16,77 E=16,82 .

 

[synthetic]

I created a second version of the checkplot with voltages. This has the circuit board a little lighter which makes the text more readable.

http://www.jefflaity.com/misc_pix/1176_revh_checkplot_volts.gif

I did another one where I flipped this diagram horizontally, which makes it easier to find test points from the back:

http://www.jefflaity.com/misc_pix/1176_revh_checkplot_volts_rev.gif

I left the old one up at the previous link in case anyone prefers that.

Now, on to my unit. I have it to the point now where it passes audio and seems to compress it, but the input pot doesn't do anything. Voltages look reasonably correct overall, and I don't see any obvious solder bridges. I can measure the change from 10k to 0 with my meter as I turn the knob.

Now, I have the entire board stuffed: both transformer and op amp inputs. I planned to listen to both and choose one, or possibly add a switch. I added a jumper from pad 1 in the middle of the board to pad 1 of the input pot for the transformer balanced section. I tried desoldering this jumper but this doesn't help. I get no input from the transformer balanced section. Audio passes from the op amp section, only with the input knob doing nothing.

Again, this is using the mnats board (which is now famously featured on analogindustries.com). Let me know if you have any guesses. Thanks, -jl

 

[synthetic]

If I measure the input pot connections on the board, I can see the resistance change as I turn it. If I disconnect the pot, the signal goes away. If I short connections 1 and 2 together, it acts the same as if the input pot is connected. Any clues? Thanks.