All things G1176 - the new "repost" thread.

[gyraf]

Takes a long time and a lot of brain work to analyze data like that to guesstimate an error - I don't have that these days, sorry. Have you tried reading through this very-long thread? It's almost unlikely that you have come across a whole new category of malfunction...

Jakob E.

 

[RyanB]

Hallo Jakob,

thanks for the replay, but that sounds not good for me!

Maybe you can help me though a little bit.

I measured again the signals on the base without the FET Q1 and I get the following voltages:
Input:            1Vpp
Q2:                0,9Vpp
Q3:                0,150Vpp
Q4:                21,8Vpp
Output Pot:    20,9Vpp
Q5:                20,9Vpp
Q6:                1,08Vpp
Q7:                1-2,4 Vpp
Q8:                30,3Vpp
Q9:                29,5Vpp
Output:        14,7Vpp

To understand the schematic I simulate it with Microsim (National Instruments).
On the base of Q5 I get 2Vpp with full output pot.
Then I reduce the output pot to get 500mVpp at the base of Q5. Then I get 357mVpp at Q6 and Q7 and 2,6Vpp at Q8 and Q9. The Output shows me 2Vpp.
But at the Troubleshooting at axtsystems the voltage on Q6 and Q7 must be 20mVpp and Q8 and Q9 must be 2Vpp, is that right?

Greetz,
RyanB

 

[L-event]

Hi
I am building the 1176 Rev #J and all my Voltages in the Signal Pre-amp section are wrong. All the other voltages, Q5-Q15 are correct.
I checked everyting 4 times (especially the resistors) but I am not able to find my mistake. I hope somebody has got an idea where to look closer.
An Audio Signal is passing through the whole compressor, so this at least is working. 
The blue Voltages are mine.



Thank u allready,
Levent

 

[gyraf]

Levent,

You have same voltage on both collector and emitter Q2 (1V) - this indicates a short, dosn't it?

Rule of thumb (npn's around here): Emitter must be ca. 0.6V below base. Collector must be higher than both.

Jakob E.

 

[L-event]

Hi Jakob,
I checked it. No connection between Emitter and Collector of Q2. Resistance is about 1 M Ohm.
I tuned a little bit on R16 to see what happens. Now there is a slight difference between E und C of Q2.  The Emitter has got now the lowest voltage! I also replaced Q2, nothing changes.
I uploaded a new pic.


Levent

 

[L-event]

When I turn on the power the Resistance between the Emitter and Collector of Q2 drops down to 80 Ohm. This is the Mistake.
I have already replaced it but, I am going to do it again. And I will replace the Capacities around. Just in case.

Thanks,
Levent

 

[SmitH]

Hi Guys.
I'm building a stereo 1176 J unit. OEP in and out transformers.
The left channel works fine, but the right channel has no signal passing through it. The VU is pegged in GR mode.
Checked with the scope, there is signal present at the primary of the input transformer, but not at the secondary. (I have swapped transformers between units and they work fine)
I have also replaced the IC. Any ideas what might be causing this?

 

[gyraf]

if no signal on the secondary side of transformer, either a short or a broken pcb trace.

 

[dgoszillai]

HI,

i'm finally wiring my dual 1176
i have a question about the "4" pad. it says :

When I wired this particular unit, I used ordinary stranded wire for this point. Looking at the schematic, the point between the ratio switches and the Gain Reduction Off switch is also shown unshielded. But it may be beneficial to use shielded wire here, since that is what is used after the switch.

ok i can use shilded cable but where to i solder the shield ? do i leave it not connected to any ground ? or do i solder it on the out pot ground on the ratio board ? 

and i can't find detailed info on how to wire the tranformer to the PSU board to the main pcb. there's lots of post + Mnats page but i'm too noob to figure out what to do with this
i have this transfo wich says :

14Va
prime 115v (blue/blue) / 115v (white / white)
second 24v (black / red) /24v (yellow / blue)
it's for europe (220v)
so what should i do with this + psu board + socket and fuse ? 

last question. for the moment i'm only wiring one channel of the 1176 because parts are missing on the other one.
will it be ok to wire only one channel from the psu board or could that be a problem ?

 

[dgoszillai]

ooh i got it.
i wrote on the 1st and didn't wish you guys a happy nu year ! soorryyy ! pff you were so upset you didn't answer naa i understand.  ;D

ok apologized now. .. anyone can answer me pliiz ?

 

[WNStudios]

Have anybody used UA's original pushbuttons? I got mine on auction and i managed to figure out how to wire the Meter PCB but i'm having a harder time with the Ratio. The labelings are ofcourse different so i could perhaps need some help tracing it.

 

[audiophreak]

Passes signal, but I'm getting a hum.
The hum is controlled by the output pot.
As I turn the output up, it gets quiet until about half way, then gets really loud.

I have both XLR's grounded to chasis, and using Mogami shielded cable.

Quite a common problem it seems.
1. Check the grounding of your front panel. I have seen ungrounded front panels cause this. Even though the rest of the chassis is grounded, unless the front panel is wired to gound it may have some resistance between it and ground. A quick check with a piece of wire.
2. Check the location of your mains transformer and its associated leads. Move them around and see if it changes amplitude. Find the quietest spot. If the contruction is really packed in you may need to add a metal shield in front of the transformer.

I've seen a few of these come up in the searches , but no one posts back with what worked ...

so this is what is happening in my dual unit , checked all of this - problem persists ,  I have the short leads from Input pin 1 to XLR jack screw with star nut and paint scrapped off , IEC Earth to Chassis Bolt, using an mnats +/- supply to both Rev.J boards .

  This is the WEIRD part ... using my cheep alligator test lead , I clamped on to Chassis Ground bolt and connected the other end to the 0v output from the PSU - Hum goes away - ran a permanent wire with soldered eye from bolt to 0v - Hum is still there !!  .. pull wire out of connector on PSU PCB and clip alligator test lead to it . start toughing things , and when 0v touched again - HUM GOES AWAY !!!!  it seems I have a MAGIC test lead -  any one got any Ideas on whats happening here ???

  Thanks for any and all help / suggestions ,
                                                                    Chip

 

[gswan]

The only grounding I ever do is to connect the PSU 0V to chassis ground. That's a single point only, anything else could cause a loop if you are not careful. Maybe you need to remove all other connections to chassis ground first and then connect the 0V PSU point to chassis ground.

 

[audiophreak]

The only grounding I ever do is to connect the PSU 0V to chassis ground. That's a single point only, anything else could cause a loop if you are not careful. Maybe you need to remove all other connections to chassis ground first and then connect the 0V PSU point to chassis ground.

  Thank You gswan  .... start from square one and work out    ( forest through trees )

 

[jwrightzz1234]

I am putting together an 1176 and its looking like this part is no longer sold on mouser and is obsolete? Does anyone have any ideas for a replacement?

 

[gswan]

Either look elsewhere *they are available) or use a 2N5457 instead.

 

[warpie]

Hi guys,

A rather simple question...

I have some mnats rev h boards from 2005. Is this the right thread to look for information? 

I'm a bit confused about G1176, Rev J and Rev H differences...

Thanks
w.

 

[gyraf]

This thread is mainly for the G1176 board - the mnats boards are probably covered elsewhere in detail.

But there's only minute differences

Jakob E.

 

[warpie]

OK, thanks Jacob.

 

[Spaturno]

i finish my mnats + psu few days agoo, i get -10.78v and no more then +20v, i have a 30VA toroidal transformer 0,5 A is maybe to less for the board? Also the VU meter is not working only in GR mode i can see it moving.
Checking the unit with my ears and with a oscilloscope is anyway doing what it should.