All things G1176 - the new "repost" thread.

[dukasound]

Hi
I wanna build G1176 but with 0-12. Can I use this circuit with pot like with Lundahl use or I must use dual pot for "T" atenuator like on original schematics.
Also where to find this pot.
Thanks
Duka

 

[Svart]

I want to get rid of the meter switch and just run a VU. I am unclear how to do this and can it be done? I also have other questions about where wiring goes as i haven't seen any clear diagrams.. where does the input go if you aren't using the input trafo? what's the 3 pin header next to the output header? things like that.. i've been trying to read this 34 page thread, and others but i'm sick and drowsy and nothing is making sense today!

I need :guinness: :guinness: :green:

 

[kdawg]

I accidently put in BD517 and BD518 both backwards on another 1176 I was putting together (Labs V7 board). Anyhow, I smoked R40/41 (4R3 resistors) instantly. So after replacing BD517/518 and R40/41, it still doesn't seem quite right. What else should I replace or check down the signal line? Did this end up putting like 30+ volts on the rest at the junction of R40/41?

Thanks

-kdawg

 

[Rob Flinn]

I want to get rid of the meter switch and just run a VU

Do you mean run it as a VU as in not showing gain reduction. If so some people say this changes the sound, though I can`t vouch for this. Some people will only use the meter in VU mode for set up & switch to GR when its actually doing the job so to speak. The difference is when the meter shows GR it is buffered, but this is not the case in VU mode when it is simply strapped across the output.

where does the input go if you aren't using the input trafo?

If you`re not using the input transformer then you use the input header that is next to the output.

What you may find useful is to download the board layout PDF for this project from the GYRAF site. This has the connection details on it.

 

[gyraf]

[quote author="kdawg"]I accidently put in BD517 and BD518 both backwards on another 1176 I was putting together (Labs V7 board). Anyhow, I smoked R40/41 (4R3 resistors) instantly. So after replacing BD517/518 and R40/41, it still doesn't seem quite right. What else should I replace or check down the signal line?[/quote]

The driver transistors feeding the output pair will often be killed as well, when making this mistake..

Jakob E.

 

[Svart]

thanks Rob!

well i could use it in GR mode more to tell you the truth. I want to get rid of the switch between gr-vu. i'm also putting two mono 1176's in one box and would like to use one vu meter also with a swtich to switch the meter between the two.

any thoughts?

 

[kdawg]

I forgot to ask about this way back when...

I have 1/4" TRS and XLR jacks for input and output, but I never isolated the 1/4" jacks from the chassis. Do I need to even if I don't have any hum problems? I thought this might affect the levels of input when using balanced.

thanks.
-kdawg

 

[Svart]

shouldn't need to if you aren't having problems with ground. it shouldn't affect the levels at all unless there is a problem either.

cheers! :guinness:

 

[jensenmann]

Hi everybody
I have already two G1176 running with bestsounding result. But I was wondering about the behaviour of the VU and the low output level (using Gustavs PCBs and only hum-cut-mod). Investigating this thing I realized that the original schem on gyraf´s site says 100k for R54(tracking adjust) but the silksceening on Gustav´s PCBs say 500K for R54 and Gyraf´s bill of material says 470k for R54. My boards were stuffed with 500k so I changed them to 100k according to the original schem. This was the solution!!! More output Volume, the meter shows what I hear and the tracking adjust pot is no mor full counterclockwise as it was with 500k.
Any comments?

:guinness: :sad: :guinness: :? :guinness: :grin: :guinness: :green:
Jens

P.S. Mnats PCBs say 100k on silkscreening and bill of material for R54
P.S.2: heavy thanks to everybody here

 

[gyraf]

jensen,

The 500K in stead of 100K trimmer is just to have a broader adjustment range in case of less-than-brilliant FET matching.

It makes no difference whatsoever - other than that you can dial in the same values, plus some more..

Jakob E.

 

[jensenmann]

oops




I promise next time I´ll read the schem before posting subjective thing.
But there is definitely more output volume (because yesterday I installed a new poweramp) :grin:

cheers
Jens

 

[heybluez]

I might as well post to the big one....

I have signal passing through. I can turn the input and output and something happens. I can play with the Q Bias trimmer and it does things. In fact, I set the Q Bias trimmer without much incident.

When I tried to set the GR (-6db) I set the input and output to 50 mv (1 khz) and then switched to GR mode. I turn up the input level (the source, of course) and it does not seem to do much. I can never get have the input level on the output. I did also notice that there seems to be some GR when I have switched the lorlin to the complete counter clockwise position. This brought me to the possible conclusion that I have put that in the wrong way. Could this possibly be what is causing the issue? I am considering just desoldering it anyway and flipping it just to see what happens...but I am curious if anyone out there has any ideas.

Thanks!
Michael

 

[kdawg]

Could someone be so kind as to post an input / output voltage w/test tone of their working G1176... something like:

Freq: 250 HZ
(Un)Balanced Input

Ratio: 1:4
Input Knob: 1/4 up
Input Voltage: 0.72 V (AC)
Output Knob: 1/2 way
Output Voltage: 0.5 V (AC)

Ratio: 1:4
Input Knob: 1/2 way
Input Voltage: 0.72 V (AC)
Output Knob: 1/2 way
Output Voltage: 0.6 V (AC)

Ratio: 1:20
Input Knob: 1/4 up
Input Voltage: 0.72 V (AC)
Output Knob: 1/2 way
Output Voltage: 0.3 V (AC)

Ratio: 1:20
Input Knob: 1/2 way
Input Voltage: 0.72 V (AC)
Output Knob: 1/2 way
Output Voltage: 0.56 V (AC)

I'm just having a heck of a time figuring out why my unit is limiting with basically anything I put into it. It's really unusable right now. Thanks a ton.

 

[kdawg]

Could this be my input problem...

BC107 instead of BC107B's? Could that really change the threshold points?

Ic = 2mA, Vce = 5V - hFE for BC107: 110 to 450
Ic = 2mA, Vce = 5V - hFE for BC107B: 200 to 450

f= 1kHz
Ic = 2mA, Vce = 5V - hfe for BC107: 250
Ic = 2mA, Vce = 5V - hfe for BC107B: 300

I want to use these 1176s so bad, but I just can't put any signal from a preamp into it without squashing it like crazy, thus getting really low output. I've used real 1176s and can usually set the input around 10 o'clock, output around 2 o'clock and you're set.

All voltages match the schematic... I've built 4 channels, they all act the same. Definitely BF245A's there.

-kdawg

 

[heybluez]

[quote author="idylldon"]
Here are the voltages I measured for each transistor:

E B C
Q2--.51--1.03--1.83
Q3--1.20--1.83--11.85
Q4--11.36--11.96--30.5
Q5--4.41--4.87--28.7
Q6--29.3--28.7--14.47
Q7--30--29.3--14.47
Q8--13.84--14.47--30.5
Q9--13.80--13.19--0.0
Q12--2.38--2.88--9.75
Q13--9.17--9.76--30.5
Q14--1.62--2.17--10.69
Q15--10.15--10.69--30.5
[/quote]

Ok. I definitely think I have some serious issues in my GR Control Amp Section.

For those that did not know what I had to do....I built the board and I think I shorted the 7824 (regulator) and caused some serious things to happen in the circuit. First, it blew up the 5532 I had in at the time as well as the big 1.1k resistor! hehe..that was fun. Anyway, I replaced the 1.1k and the regulator and it powered up great. I have the 30V/-10V we are looking for. Then it would not really pass audio. SO...I changed out the first FET and replaced transistors Q2,3,4. Now it passes audio just fine. Please note I am also bypassing the 5532 and using the input transformer (lundahl). Now when I play with the QBias something happens so that is a good sign. The problem is that it does not really seem to compress the way it is supposed to. I feared that I might have destroyed some other transistors in the circuit so I checked the voltages. This is what I found:

E B C
Q2--.56--1.09--1.84
Q3--1.20--1.86--12.95
Q4--11.3--11.8-- 29.53
Q5--4.4--4.8--28
Q6--28.5--27.9--14.45
Q7--29.64--28.99--14.73
Q8--13.81--14.48--29.87
Q9--13.77--13.14--0.0
Q12--22.9--8.23--26.60
Q13--25.87--26.33 --30.03
Q14--29.98--4.88--5.45
Q15--4.86--5.45--30.01

When I compared these to some other ones I found listed in this thread (see above quote for one example) Q12,13,14,15 seemed to be WAY off. This brings me to the conclusion that something is obviously wrong with the GR control amp. This, obviously, would cause some issues in regards to compression!

Anyway, before I go and replace all these transistors....could something else be happening that I need to check first? Any input voltages to check?

Thanks!
Michael

 

[Greg]

kdawg:
Did you rewire the output tranny for more gain? How is it wired... 2:1, 1:1, 1:2 ???

I rewired mine 1:1 and I like the results... I'm thinking about actually going to 1:2 configuration for even more gain.

 

[gyraf]

Michael,

Q12, Q14 looks "most" wrong. Try changing these - check for shorts, component values, and orientation around those.

Jakob E.

 

[idylldon]

[quote author="kdawg"]Could this be my input problem...
BC107 instead of BC107B's? Could that really change the threshold points?[/quote]

I'm using BC107 (no suffix) in mine and they seem to work fine. All measurements are within spec and the calibration went smoothly.

I also did the 1:2 OT mod, which gave me more output, but I don't think that's what you're up against here. While the input control is sensitive, I usually end up at the 10:00 position as you mentioned and the ouput anywhere from 12:00 - 2:00.

Anyway, I just wanted to let you know the BC107 work OK in my units to help eliminate something. I wish I could offer more help, but I'm still at the steep end of this learning curve.

Cheers,
--
Don

 

[kdawg]

I have the unit wired 1:2. I'm going to try replacing both Q1 and Q10 FETs, I only socketed the Q1 FET so I'll add another socket. It seems that the line amp section is working OK, as I can get unity out very easily.

If I remove Q1 and put the unit it GR, should there still be any gain reduction measured on the output?

If I apply a -30db signal (.0245 VRMS, referenced to 0dB = 0.775 VRMS, correct?) unbalanced, + pin 2, - pins 1&3 tied then measure Input Pot Pin 1, I should get 0.245 volts also right?

Then - if I switch to a balanced signal, applying -30dB (do I measure 0.245 VRMS across + to GND or + to -?), + pin 2, - pin 3, ground pin 1 and measure Input Pot Pin 1, I should still have 0.245 volts right?

I'm trying to isolate the 5532 input stage to make sure this isn't a balanced/unbalanced issue.

Thanks everyone for your help!

-kdawg

 

[gyraf]

If I remove Q1 and put the unit it GR, should there still be any gain reduction measured on the output?

There will not be any gain reduction, but the meter (Q10) will still allow meter to indicate the now-not-happening GR.