All things G1176 - the new "repost" thread.

[deanp920]

Orson,

You must have just changed something for the worse on your output transformer. You JUST had 6.8V(previous page) on the output XLR with the FET pulled and now you have 3.2V.

Go back and see what you just did to that output transformer!

What is good to see is that things are looking much better gain-wise when you put the FET back in(maybe something wasn't seated before, or the Qbias trimmer was set way wrong). Everything in terms of gain stays about the same, which is good, except you need to fix your OPT so it works like it did before.

That dc voltage on the release wiper should be a NEGATIVE number(black probe to ground). Go back and verify that. While you are measuring there, run the Qbias trimmer from one extreme to the other, note the voltage at each extreme, and leave it set for the highest negative voltage(should be better than -2Vdc).

The idea will be to reduce this negative voltage just a a tad with the Qbias trimpot until the output falls just 1db. This puts Q1 right at the beginning of its conduction.

But leave the Qbias trimpot at max bias for now and get that OPT sorted out so you get back your ~6.8V with the FET installed. Just back up and carefully go through your OPT wiring and hopefully you'll find the error. Power down and use your ohmeter to verify jumper connections and trace cuts, if needed.

If you are confused, let us know. I think we're close. Just stay focused and bear with me a little more.

Dean

 

[deanp920]

OK I get -1.5 dc mV with the trimmer all the way cw and the release knob set to full CW. I assumed that this is the "minimum" setting you meant? Well, anyway, thats what I did. And now the result with the Q-bias trimmer all the way CCW and the release knob still set full cw: -2.504 dc V

No, I meant full CCW on the release pot; sorry. What you have looks great, though, considering you have the release pot full CW.

Check my previous post(I was writing it when you posted last) and come on back.

Dean

 

[orson whitfield]

Ok this is not my last post tonight. I have checked ten times what i have done and according to what I see on the PCB diagram i have correctly wires the output tranny. And yes I have a lower Voltage than beofre. Maybe a cable got loose somewhere let me check OR someone typed the instructions for the mod incorrectly. Are you sure this is correct the way it is printed on the quote I presented on this page of the thread?

 

[orson whitfield]

[quote author="deanp920"]Orson,

You must have just changed something for the worse on your output transformer. You JUST had 6.8V(previous page) on the output XLR with the FET pulled and now you have 3.2V. [/quote]OK It was my fault I was measuring star ground instead of pin 3! That's why I got a different voltage reading. Now I have to change the output tranny jumpers back to the new, correct placement and make sure I still have the higher voltage measurement on pins 2 and 3. Sorry about this mix up> I did not know ground was different than pin 3.


[quote author="deanp920"]What is good to see is that things are looking much better gain-wise when you put the FET back in(maybe something wasn't seated before, or the Qbias trimmer was set way wrong). [/quote] This is VERY possible. Especially since there are things I have been measuring using AC on my DMM instead of DC. I just didn't know this. Sorry. And it's very possible Q1 was not seated correctly. I did let the leads from the DMM brush by the Q1 once.
[quote author="deanp920"]That dc voltage on the release wiper should be a NEGATIVE number(black probe to ground). Go back and verify that. [/quote] Yeah it was negative I didn't tell you and I should have been specific. i see that there is a difference between the two now. [quote author="deanp920"]While you are measuring there, run the Qbias trimmer from one extreme to the other, note the voltage at each extreme, and leave it set for the highest negative voltage(should be better than -2Vdc).
The idea will be to reduce this negative voltage just a a tad with the Qbias trimpot until the output falls just 1db. This puts Q1 right at the beginning of its conduction. [/quote] You see, here is a prime example of what's been going wrong for me if what you have posted here is a reiteration of what the Q-Bias calibration setup is. If so, I have been measuring this in AC not DC, as I should have. Well, the good news is all this has taught me a lot and shown me that I had my tranny Jumpered incorrectly. This is good stuff.

[quote author="deanp920"] But leave the Qbias trimpot at max bias for now and get that OPT sorted out so you get back your ~6.8V with the FET installed. ... Power down and use your ohmeter to verify jumper connections and trace cuts, if needed.[/quote] I don't know what exactly to do to check the resistence (sp?) with my DMM ohmeter section, so let me just put that out there right at the start before i go measuring things incorrectly again. In the mean time I'll put the jumpers to where they should ne and follow your new directions and post the results. Sorry for the long posts.

 

[orson whitfield]

OK changed the jumpers back to the correct position (4 to Y and 1 to X).[quote author="deanp920"]You must have just changed something for the worse on your output transformer. You JUST had 6.8V(previous page) on the output XLR with the FET pulled and now you have 3.2V. [/quote] OK now I have measured 6.49V.


[quote author="deanp920"]That dc voltage on the release wiper should be a NEGATIVE number(black probe to ground). Go back and verify that. While you are measuring there, run the Qbias trimmer from one extreme to the other, note the voltage at each extreme, and leave it set for the highest negative voltage(should be better than -2Vdc).[/quote] It is . I have -2.041 dc V.


Ok my brain is getting fried. What do i need to measure now?

 

[deanp920]

Orson

Ok my brain is getting fried. What do i need to measure now?

OK, I'm ready to call it a night.

At this point you can turn the Qbias pot the other way until that 6.49Vac drops to something like 6Vac. I can't find my calculator right now, but you're looking for a ~1db drop. That sets your Qbias.

The compressor should be working correctly now, with the exception of the meter, which is ready to be calibrated.

Let me know where you're at. :grin:

Dean

 

[orson whitfield]

One thing I need clarification on is wether or not the values are supposed to be similar with the Q1 removed and when it's present? I get different dc voltages on the release pot with it removed and with it present.

 

[deanp920]

One thing I need clarification on is wether or not the values are supposed to be similar with the Q1 removed and when it's present? I get different dc voltages on the release pot with it removed and with it present.

I'm assuming you are referring to the negative voltage measured off the wiper of the release pot from ground. No, that should not change one bit when the FET is removed. Only the signal level at the output XLR should fall a bit.

What Vdc are you getting on the wiper of the release pot under these circumstances:

Release full CCW FET in

Release full CCW FET out

Release full CW FET in

Release full CCW FET out

Dean

 

[orson whitfield]

[quote author="deanp920"]

One thing I need clarification on is wether or not the values are supposed to be similar with the Q1 removed and when it's present? I get different dc voltages on the release pot with it removed and with it present.

I'm assuming you are referring to the negative voltage measured off the wiper of the release pot from ground. No, that should not change one bit when the FET is removed. Only the signal level at the output XLR should fall a bit.[/quote] Mine does change dramatically. I get a -.816 dc V with it in and -2dc V with it out.

[quote author="deanp920"] What Vdc are you getting on the wiper of the release pot under these circumstances:

Release full CCW FET in[/quote]0.816dc V

[quote author="deanp920"]Release full CCW FET out[/quote] -2.026dc V

[quote author="deanp920"]Release full CW FET in[/quote]-2.513dc V.

[quote author="deanp920"]Release full CCW FET out[/quote] I assume you meant CW here? If so I get -2.799dc V.

Also, remember I could not get the GR meter Tracking set because my xlr output voltage was always a 1/3 of the input voltage no matter how much or little I attenuated the input to the input xlr from the sound generator. According to the instructions for calibration, step four is to get unity gain and then turn up the input signal at the source until you reach a point where the output level is half the input.

 

[deanp920]

Ok, here are my numbers measuring from the release pot wiper to ground:

Release pot full CCW FET in: -2.22Vdc
FET out: -2.22Vdc

Release pot full CW FET in: -2.15Vdc
FET out: -2.15Vdc

The first thing that bothers me is that you get more negative bias with the release pot full CW, and you I more with it full CCW. Double check the wiring on your release pot, as well as verifying its' component value.

Make sure you have the pins of your FET oriented correctly.The shape of the FET should match up with the overlay on the PCB.

If you still haven't found an error, try another FET.

Lastly, try another FET in the Q10 socket and also verify its' orientation.

I very much suspect that you have a wiring or component error somwhere in the electronic vicinity of Q1.

Try these suggestions and I'll think some more about this.

In the meantime, your project should sound good as a line amp with tons of gain. Just leave Q1 out. It would be nice at this point to verify your project's functionality in this capacity.

We'll get it!

Dean

 

[orson whitfield]

Which pot wiper do I use, Dean? Because the bottom one gives me -2.09 dc V with FET in or out and with the release pot set to full CW or full CCW. I thought I was supposed to use to top one. I think I am measuring incorrectly. I have the FET set in correctly.

The unit is passing audio and does have much gain. I don't know if it's working correctly. When I measure the output XLR I use the red lead on the#2 pin but do I use the black lead on pin #1, pin#3 or star ground? Each one gives me a different measurement. I still have pins #1 and #3 connected on the input XLR and not connected on the ouput XLR.

 

[deanp920]

Which pot wiper do I use, Dean?

There is only one wiper, and it is almost always the center contact. It corresponds to the arrow you see on the schematic. The other two contacts are each end of the resistor, commonly referred to as the high and low sides. I should have been more specific.

Repeat the measurements using the center contact and ground and let me know what you get. Then we'll be caught up. Go ahead and try a new FET while you're at it if things still seem wrong compared to my figures. Your negative voltage may read a bit higher, since your Qbias pot is at max and mine is set back already. It's the differences in voltage that are of concern here. Pulling the FET should do nothing; turning the release pot back and forth should only cause a slight change(.05V or so). If it still seems screwed up, change both FET's(Q1&Q10) and see if that helps.

Also, with the release pot full ccw, briefly turn the Qbias pot to its' other extreme; you should read 0Vdc. Then put the Qbias trimmer back where it was. If the release pot needs to be full cw to read 0Vdc, then you have the two outer wires on the release pot mixed up, assuming you have the center contact wired correctly. Check it out.

The unit is passing audio and does have much gain.

That's good. Is that with the FET out?

When I measure the output XLR I use the red lead on the#2 pin but do I use the black lead on pin #1, pin#3 or star ground? Each one gives me a different measurement. I still have pins #1 and #3 connected on the input XLR and not connected on the ouput XLR.

Measure across pins 2&3. For an AC measurement, probe polarity does not matter.

You may use pin 1 or star ground only if either pins 2 or 3 are grounded also, which makes the output single ended, or unbalanced. Pin 1 should be grounded. Measure across output XLR pins 2&3 only and you'll be OK.

Dean

 

[orson whitfield]

[quote author="deanp920"]
Repeat the measurements using the center contact and ground and let me know what you get. [/quote] will do. see below.

[quote author="deanp920"]Go ahead and try a new FET while you're at it if things still seem wrong compared to my figures. Your negative voltage may read a bit higher, since your Qbias pot is at max and mine is set back already. It's the differences in voltage that are of concern here. Pulling the FET should do nothing; turning the release pot back and forth should only cause a slight change(.05V or so). If it still seems screwed up, change both FET's(Q1&Q10) and see if that helps. [/quote] see below, it's looking good.

[quote author="deanp920"]Also, with the release pot full ccw, briefly turn the Qbias pot to its' other extreme; you should read 0Vdc. Then put the Qbias trimmer back where it was. If the release pot needs to be full cw to read 0Vdc, then you have the two outer wires on the release pot mixed up, assuming you have the center contact wired correctly. Check it out.[/quote]I get -000.9 mV. I guess that's close enough to 0Vdc.


[quote author="deanp920"]Quote:
The unit is passing audio and does have much gain.
That's good. Is that with the FET out?[/quote] it passes audio with the FET in and out. It does get louder with it out though.

[quote author="deanp920"].... Measure across output XLR pins 2&3 only and you'll be OK. [/quote] I did this this time - makes a difference



[quote author="deanp920"]OK, I set my G1176 up just like yours with the Q1 pulled and a 50 mV, 200Hz input signal. Input and Output cranked. Unit set to bypass.[/quote]
Ok I have this exact setup now except 49.8 mV is the closest I could get to 50 this time..
[quote author="deanp920"]Input wiper: 50mV[/quote]I have 49.6mV.
[quote author="deanp920"]Output wiper: 1V[/quote] I have 1.059V.
[quote author="deanp920"]C15 transformer side: 3.8V[/quote] I skipped this one.
[quote author="deanp920"]Output XLR: 6.8V[/quote] I have 6.63V :grin:
[quote author="deanp920"]Now I put the FET back in and I get...
Input wiper: 50mV[/quote] I get 49.6 mV
[quote author="deanp920"]Output wiper: .96V[/quote]I measure 1.059V with the q - biad trimmer all the way to one side.
[quote author="deanp920"]C15 transformer side: 3.4V[/quote] I skipped this one.
[quote author="deanp920"]Output XLR: 6.13V[/quote] I have 6.63 V

[quote author="deanp920"]With no signal applied, I/O max, Attack and Release max, Ratio 20:1, Bypass mode, I get about -2.2Vdc from ground to any pin on the release pot. The reading is the same whether Q1 is in or out of it's socket.[/quote] I get -2.806 Vdc with it in and out. :grin:

Are things looking good. :?

 

[soundguy]

dont know if this was in the 58 page old post or not, but Im just building a rotary switch for an old 1176 and looking at the nuke mod for the gyraf switch, couldnt you just program the lorlin for 5 positions, wire a jumper from 1-5, 4-5, 7-11, 10-11 and get your "all in" position as the fifth position on the switch? This would save you adding a dpdt if it works...

Is my thinking right here?

dave

 

[deanp920]

dont know if this was in the 58 page old post or not, but Im just building a rotary switch for an old 1176 and looking at the nuke mod for the gyraf switch, couldnt you just program the lorlin for 5 positions, wire a jumper from 1-5, 4-5, 7-11, 10-11 and get your "all in" position as the fifth position on the switch? This would save you adding a dpdt if it works...

Is my thinking right here?

Dave, I can't remember anyone trying that, but it is pretty hard for me to visualize right away. There sure are a lot of different ways to skin a cat with those rotary switches; the possibilities are incredible.

Please pursue this and let us know if it works; I don't doubt that it might.

OK Orson,

From your last post things are looking very good. I don't quite understand how you are hearing a level shift with the FET in or out when the output measures exactly the same whether the FET is in or out. I'll assume a minor miscommunication and leave it at that unless you think otherwise.

The next thing to do is back off the Qbias pot while monitoring the output XLR until the output drops a very little bit(about 1db; use the formula), say to about 6Vac. That sets the Qbias. Hopefully you will turn the pot a bit before the output starts to drop; that just shows that you are truly approaching the cutoff point and not already past it even with the Qbias pot at max.

Then you can go ahead with the meter calibration procedure. Stick with the 200Hz frequency, though, so you can make accurate AC measurements with your DMM. It is really handy to use a meter on the input and another meter on the output so you can monitor things simultaneously.

Take your time and let us know how its going. Ask all the questions you need to.

Dean

 

[orson whitfield]

OK All is done and calibrated. It sounds good. I guess it's working. Perhaps, in my mind I was imagining a different, more "in your face" compression from the 1176. But instead it sounds gentle. That is ofcourse if this is working right but i guess it is. The last problem is the intermitent crackling. It comes and goes but always doesn't start happening until the unit has been powered on for thirty minutes. The crakiling is not constant or the same in duration when it comes up. It's also not very loud but it's definately noticable. How many milliseconds is the attack when set full CW? And yes the volume definately gets louder when the FET is removed. :sad: I get the feeling I'm not out of the woods yet.:roll:

 

[mnats]

...couldnt you just program the lorlin for 5 positions, wire a jumper from 1-5, 4-5, 7-11, 10-11 and get your "all in" position as the fifth position on the switch? This would save you adding a dpdt if it works...

Looks like the common connections are not shared by the slam/nuke implementation:

http://www.gyraf.dk/gy_pd/1176/slam.htm

So you need another switch to do it Jakob's way.

 

[rafafredd]

I´m searching for semiconductors and I´ve found several types of bc107. there is A, B and C versions, probably different gain. what type is the best for 1176?

 

[deanp920]

Raffafred,

I´m searching for semiconductors and I´ve found several types of bc107. there is A, B and C versions, probably different gain. what type is the best for 1176?

Most folks seem to be going with the C type.

Orson,

And yes the volume definately gets louder when the FET is removed.

After doing the Qbias calibration, that is to be expected. If you think it is a problem, put in the effort to measure and calculate HOW MUCH louder it gets with the FET out so we can discuss something concrete.

How many milliseconds is the attack when set full CW?

I don't know. Did you check the UREI manual?

The last problem is the intermitent crackling. It comes and goes but always doesn't start happening until the unit has been powered on for thirty minutes. The crakiling is not constant or the same in duration when it comes up. It's also not very loud but it's definately noticable.

Does this happen with or without input signal? The unit will distort on low frequencies if the release pot is full CW and even more if the attack pot is full CW also. Somehow this does not sound like your problem, though. Take a pencil eraser or other non conductive probe and gently wiggle FET's, transistors and other components while the unit is misbehaving to see if you can find one that makes it crackle more when you wiggle it. My first instinct would be to pull Q1 when it starts crackling and see if it goes away. Also, a partly fried resistor might be doing it. Smell the board for burnt spots and inspect all the resistors with a magnifying glass. Bad solder joint? Loose socket connection? All things to consider. When it starts crackling, turn down the input control to see if that stops it. If it does, then it is probably something before the input pot. If not, then turn down the output control and apply the same logic. If the output control won't affect the crackling, then the problem is most likely somewhere in the signal line amp after the output pot. Use similar thinking when switching between GR and Bypass. Narrow the possibilities down as much as possible in the beginning.

Dean

 

[soundguy]

[quote author="mnats"]

...couldnt you just program the lorlin for 5 positions, wire a jumper from 1-5, 4-5, 7-11, 10-11 and get your "all in" position as the fifth position on the switch? This would save you adding a dpdt if it works...

Looks like the common connections are not shared by the slam/nuke implementation:

http://www.gyraf.dk/gy_pd/1176/slam.htm

So you need another switch to do it Jakob's way.[/quote]


Isnt that lorlin a 2 pole switch?

dave