gyraf

Re: All things G1176 - the new "repost" thread.
« Reply #3840 on: May 23, 2018, 02:25:03 AM »
Adjust it?
..note to self: don't let Harman run your company..


Re: All things G1176 - the new "repost" thread.
« Reply #3841 on: May 23, 2018, 02:36:07 AM »
Found it. Cold solder joint at pad 18.
P&P Sound Studio

Zebra_PD

Re: All things G1176 - the new "repost" thread.
« Reply #3842 on: June 13, 2018, 06:05:29 AM »
It would be very cool to have "transformer-less/transformer" input switch on the front of the unit, like two options. In my head that sounds like grate idea! :-) Components for  electronically balanced input isn't to expensive so I will keep them on the board if they don't interfere with transformer input.

Hi did you end up putting a input switch to your build? Did you get an answer if its possible to do so without having to add second/modified input amp?

Otherwise perhaps someonr else can help me with this question.

If input level is controlled by a transformer then the pot (or attenuator) is prior in the electronic chain to in the input transformer right? (if I look at the original UREI rev F for example).  But in the  UREI rev G/H the pot is AFTER the OPAs (IC2-A, IC2-B) ?

So in the transformer version the pot increases the voltage going from the input to the transformer input amp  and in the OPA version the pot decreases the voltage going from the input stage to the signal preamp stage? Or have a misunderstood the whole design difference now? Or is the first two ICs in the chain of the OPA version just to even the level of input voltage and not to directly effect the voltage of it? :)

If I by chance is correct would it then be possible to use a dual gang 10k pot, one gang to increase and the other one to decrease, to control the gain for the different input amps and then have a switch to change from OPA to Transformer based input?
« Last Edit: June 14, 2018, 08:36:28 AM by Zebra_PD »
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

Re: All things G1176 - the new "repost" thread.
« Reply #3843 on: June 21, 2018, 04:18:43 AM »
Hi guys im posting because my G1176 has an ungodly amount of hum.  :'(

Im mostly suspecting a ground loop somewhere because the hum seems to be all around the circuit. With the output turned all the way down the hum is still there, but when turned up a fraction it fades out and then comes back as its turned up more. When tracing from the input the hum starts off small and then when it hits Q3 it gets amplified to a huge hum. On the meter the GR position seems to work but the other positions are pushed to max, because of the hum. I made the recommended board cuts to try to stop the ground loop on the board but that didnt seem to help. The PSU plug ground is connected to the chassis, the transformers secondary is connected to the chassis, and the input XLR pin one is connected to the chassis. I noticed another guys had a similar issue but Im not sure if there was a solution found. Any help would be much appreciated. 

 

dirtyhanfri

Re: All things G1176 - the new "repost" thread.
« Reply #3844 on: July 14, 2018, 03:34:32 PM »
Edit: found the problem, related to the board traces.
« Last Edit: July 15, 2018, 01:42:40 PM by dirtyhanfri »
Working on it...

dirtyhanfri

Re: All things G1176 - the new "repost" thread.
« Reply #3845 on: August 09, 2018, 05:09:10 AM »
Hi

I'm struggling with a g1176, using REVH board by mnats.

The thing is, I have +29.1V and -9.5 as supply, and all transistor voltages are a bit off.

I'm using 1k2 resistor in R87 instead 1k1, maybe that's the problem?
Working on it...

Nagskof

Re: All things G1176 - the new "repost" thread.
« Reply #3846 on: August 14, 2018, 09:15:29 AM »
Thanks to this forum, Mnats and Gyraf, built two Mnats Rev H in a 2U rack with push buttons, super proud  :) Both channels are identical and I double checked all components, connection etc. Both channels pass (awesome) audio, and compression is fine, however, the VU meter on the second channel jumps to different places in GR mode when I switch between ratios. 1:4 is at 0DBu reading, 1:8 drops 7 db, 1:12 drops further and 1:20 is full left. The meters are showing compression between ratio settings, but just at different places on the scale. I have no idea where to look, failed component maybe?

Zebra_PD

Re: All things G1176 - the new "repost" thread.
« Reply #3847 on: August 27, 2018, 05:18:23 PM »
Been trying to find an answer for this question but haven't had any luck searching the forum.

The B11148 output transformer used in the original Rev F is has an extra winding then the B12614 used in the rev G/H right? but is this xtra winding needed for the G1176 design?

I know the current rev f offered my mnat is designed to incorporate the negative feedback design of the B11148 transformer but can't really figure out if the older mnat rev j board I'm using does to?

Im trying to get my build as close to the silverface I can and have couple of original b12614 I would like to use.

If anyone has the schematics for the G1176 rev 7 or the mnat rev j saved on there hard drive and perhaps could help me and/or perhaps share those I would be really greatful.

___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

gyraf

Re: All things G1176 - the new "repost" thread.
« Reply #3848 on: August 28, 2018, 04:03:46 AM »
VU meter on the second channel jumps to different places in GR mode when I switch between ratios. 1:4 is at 0DBu reading, 1:8 drops 7 db, 1:12 drops further and 1:20 is full left. The meters are showing compression between ratio settings, but just at different places on the scale.

Could be leaky FD333 diodes? Leaky (orientation?) 6u8 capacitor in that area? Wrong ratio-switch wireing?

Jakob E.
..note to self: don't let Harman run your company..

 

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