All things G1176 - the new "repost" thread.

[gswan]

You should really have everything wired up before you start testing.

 

[Biasrocks]

I have one here:
http://www.axtsystems.com/index.php?view=article&catid=34%3A1176ln&id=57%3A1176lnproblems&option=com_content&Itemid=62

I wouldn't call it 'definitive' though, since it's based on actual measurements and you must account for component tolerances and temperature. However provided you are within about 5% of the values you are OK.

If something is way off (as is currently the case with Ben's unit) then it will show up straight away and we can set about looking at the cause. Most are caused by incorrect component values and insertion of transistors. Sometimes you can get a bad transistor from new, but that's not so common (unless you are using Chinese fakes).

Great, I'll check everything out.

Thank you for you help, and your guide.

Mark

 

[Biasrocks]

I have one here:
http://www.axtsystems.com/index.php?view=article&catid=34%3A1176ln&id=57%3A1176lnproblems&option=com_content&Itemid=62

I wouldn't call it 'definitive' though, since it's based on actual measurements and you must account for component tolerances and temperature. However provided you are within about 5% of the values you are OK.

If something is way off (as is currently the case with Ben's unit) then it will show up straight away and we can set about looking at the cause. Most are caused by incorrect component values and insertion of transistors. Sometimes you can get a bad transistor from new, but that's not so common (unless you are using Chinese fakes).

Alright, here's the DC Bias numbers.

Yours

Q B C E
2 1.04 1.81 0.50
3 1.81 11.8 1.17
4 11.8 30 11.2
5 4.88 28.3 4.40
6 28.3 14.4 28.9
7 28.9 14.4 29.5
8 14.4 30 13.7
9 13.1 0 13.7
12 4.47 15.1 3.89
13 15.1 30 14.5
14 3.45 16.6 2.86
15 16.6 30 16.0

My DC Bias results

Q B C E
2 1.03 1.74 0.53
3 1.73 12.3 1.13
4 12.17 29.6 11.58
5 4.84 27.9 4.41
6 28.2 14.6 28.7
7 28.7 14.6 29.4
8 14.6 29.9 14.0
9 13.3 0 13.9
12 4.52 14.8 4
13 14.8 29.9 14.22
14 3.45 17.09 2.91
15 17.1 29.9 16.56

Looks good, yes?

I tried passing signal and I'm getting output, the compression sounds terrible .

I guess the next step is to go through the calibration procedure.

Update: I went through the calibration procedure and got the Q Bias and Zero Adjust setup. It's sounding good, all the functions are working, I'm getting compression with all ratios and attack, release working as they should and it sounds good! 

I'm getting some hum at greatly elevated input levels. I tried re-orienting wires and power transformer but it made zero difference in the hum level.

I've found the Dist trim and meter Tracking adjustment instructions on the Gyraf site, so that's next.

Update 2: DAMN! While doing the Dist Trim, I was sending a super hot 1khz tone to the 1176 and bam, lost level and now everything is distorted and low level. Must of fried something, could it be the input opamp that fried or should I look elsewhere. My DC Bias voltages check okay, but I'm getting 14.7v DC on just about every pin of the 5532 input IC and 30v on pin 8.

I pulled the 5532 and I'm getting the following voltages

Pin   DC
1      0
2      0
3      14.9
4      0
5      14.9
6      0
7      0
8      29.9

I checked the 100k and 10k resistors around the opamp and they all check out okay.

Update 3: Yep, I killed the 5532 that was in there, damn! Anyways, replaced with an OP275 I had laying around in my JH24  :, lifted the compensation cap and it's working again.

Who knew you could blow up a 5532 with a 1khz sine wave on stun.  :'(

Mark

 

[btproductionsaustralia]

ok, 3 really simple questions(for you guys, not simple for me)

If a resistor is dead or damaged will it's resistance still read as it should or will it come up as zero or low?


If the voltage on both sides of a resistor or capacitor is the same, does this mean they are not working?

Is there anyway to test a capacitor is working, even without a multimeter with capacitance?

Thanks heaps

Ben

 

[gswan]

If a resistor is dead or damaged will it's resistance still read as it should or will it come up as zero or low?

It's usually higher or open-circuit. I've never seen a resistor fail short-circuit.

If the voltage on both sides of a resistor or capacitor is the same, does this mean they are not working?

No, if the voltage is the same on both sides of a resistor it means that no (or immeasurable) current is flowing through the resistor. With the capacitor it will depend on what the cap is being used for (ie circuit topology).

Is there anyway to test a capacitor is working, even without a multimeter with capacitance?

Several, depending on its size. You can use a charge/discharge curve to calculate the value of a capacitor by virtue of the amount of time it takes to charge to a known voltage through a known resistance.
You can also determine the value of a capacitor by using a known inductor and and an oscillator to determine the resonance point (series or parallel, it does not matter) and solving for C.

 

[btproductionsaustralia]

If a resistor is dead or damaged will it's resistance still read as it should or will it come up as zero or low?

It's usually higher or open-circuit. I've never seen a resistor fail short-circuit.


Ok, so if all my resistors measure correct, than I can assume they are all ok?

If the voltage on both sides of a resistor or capacitor is the same, does this mean they are not working?

No, if the voltage is the same on both sides of a resistor it means that no (or immeasurable) current is flowing through the resistor. With the capacitor it will depend on what the cap is being used for (ie circuit topology).

So is a lack of current flowing through a resistor a problem in my case or not? ie. if a resistor measures correct resistance, is there anything more I need to do to verify it is not the problem I am seeking?

Is there anyway to test a capacitor is working, even without a multimeter with capacitance?

Several, depending on its size. You can use a charge/discharge curve to calculate the value of a capacitor by virtue of the amount of time it takes to charge to a known voltage through a known resistance.
You can also determine the value of a capacitor by using a known inductor and and an oscillator to determine the resonance point (series or parallel, it does not matter) and solving for C.



Geez, thats sounds tough...

 

[gswan]

If a resistor is dead or damaged will it's resistance still read as it should or will it come up as zero or low?

It's usually higher or open-circuit. I've never seen a resistor fail short-circuit.

Ok, so if all my resistors measure correct, than I can assume they are all ok?

Yes. Your meter is injecting a current through them and measureing the voltage across them, so the reading is a good indication that they are functioning as expected.

If the voltage on both sides of a resistor or capacitor is the same, does this mean they are not working?

No, if the voltage is the same on both sides of a resistor it means that no (or immeasurable) current is flowing through the resistor. With the capacitor it will depend on what the cap is being used for (ie circuit topology).

So is a lack of current flowing through a resistor a problem in my case or not? ie. if a resistor measures correct resistance, is there anything more I need to do to verify it is not the problem I am seeking?

No. That will depend on the way the resistor is being used in the circuit. If current is supposed to be flowing and it's not then there's a problem. If too much current is flowing then that too is a problem.

Is there anyway to test a capacitor is working, even without a multimeter with capacitance?

Several, depending on its size. You can use a charge/discharge curve to calculate the value of a capacitor by virtue of the amount of time it takes to charge to a known voltage through a known resistance.
You can also determine the value of a capacitor by using a known inductor and and an oscillator to determine the resonance point (series or parallel, it does not matter) and solving for C.

Geez, thats sounds tough...

And probably not necessary for your fault finding. The value marked on the case is usually correct, although you need to know how to read some values such as ceramic and polyester markings.

 

[btproductionsaustralia]

Geez, thats sounds tough...

And probably not necessary for your fault finding. The value marked on the case is usually correct, although you need to know how to read some values such as ceramic and polyester markings.

[/quote]

Ok, I know how to read them all, just trying to work out what to do, as the section around Q4, Q3, Q2 have all resistors working and correct resistance, capacitors are all correct, and transistors appear ok(I have replaced Q4 and Q3), so wanted to make sure that they couldn't "appear" correct but still be faulty...

 

[btproductionsaustralia]

Geoff,

After re measuring with everything re connected, there have been some new developments...
The voltages on Q2 and Q4 are now

    B        C        E
Q2 1.6      2.5      7.7-9.9(varied different times)
Q4 1.9      29.3    7.7-9.9( varied different times)

Also the previously correct Q12 and Q13 are now wacked!!

Now the voltages are jumping around constantly and won't settle on a figure!!
This goes for all B, C and E for Q12-Q15 except, Q13  c= 29.2  and Q15  c=29.2...

Also R36 burnt out...does this indicate anything specific?

Finally, I thought I better measure all pins on the voltage regulator:
they were 29.3    .2    and 36.6 
is this acceptable?

THanks

Ben

 

[gswan]

Ben,
R36 burning out indicates that you may have inserted the BD139/140 pair incorrectly (there are multiple holes to accommodate different types of transistors here). Probably zapped Q6 as well.

You've still got a problem with your input amplifier. The emitter of Q2 ahould be steady at about half a volt. If it's jumping around then you may have it oscillating. Check that you have the GND end of R14 connected.

If the GR amp is all over the place you may need to settle that first. Check the wiring of the ratio switches and have a look at that section too. With it in 'bypass' nothing should be jumping around.

 

[Biasrocks]

Okay guys, I want to thank you for your help in getting my 1176 up and running. 

I have a question regarding the transformer in option.

I've got a St. Ives 31267 line input transformer here that I'd like to use as a front end to the 1176. Is a 1:1 (2k5:2k5) configuration preferable or should I go with a 4:1 (10k:2k5) step down ratio on the 31267? Do I need the 12K terminating resistor  which is specified for the Lundal or should I be using a different value there?

Mark

 

[btproductionsaustralia]

Ben,
R36 burning out indicates that you may have inserted the BD139/140 pair incorrectly (there are multiple holes to accommodate different types of transistors here). Probably zapped Q6 as well.

You've still got a problem with your input amplifier. The emitter of Q2 ahould be steady at about half a volt. If it's jumping around then you may have it oscillating. Check that you have the GND end of R14 connected.

If the GR amp is all over the place you may need to settle that first. Check the wiring of the ratio switches and have a look at that section too. With it in 'bypass' nothing should be jumping around.

Ok I'll check the BD 139/140 though their voltages have been fine, so would be suprised if it's them...
Will check r14 and the ratio switches...

Incidently, how do i know what setting the potentiometer for ratio is on...it is a 6 position switch, and there is only bypass and 4 ratios, so is the 6th position just nothing?

Thanks

ben

 

[gswan]

Ok I'll check the BD 139/140 though their voltages have been fine, so would be suprised if it's them...
Will check r14 and the ratio switches...

Incidently, how do i know what setting the potentiometer for ratio is on...it is a 6 position switch, and there is only bypass and 4 ratios, so is the 6th position just nothing?

If you are looking at my circuit, that's where my unit differs. I've added two more compression ratio settings (which I use a lot) and used a 6-position rotary switch instead of the pushbuttons. If you are using pushbuttons just match your ratio settings with the resistors switched into circuit when that setting is dialled up. The divider chain is the same, there's just more taps off it in my version.

 

[btproductionsaustralia]

Geoff,

actually I was referring to Mnats BOM which instructed a 6 position potentiometer for the ratio board, even though there are only 4 ratio settings, so that's why I'm confused, is the first setting 'bypass' 2nd, 3rd, 4th and 5th the ratios and 6th just a blank?

Can anyone enlighten me on this?

Also, if I've got the correct voltage readings on the BD139 and BD140 could they still possibly be inserted in correctly?

Finally, I've been looking at pictures of other 1176 and noticed the VU meters have 2 sets of wires going to them, where as I only have 1 set connecting it to the meter board, have I missed something? Anyone know where to source a
"how to wire a VU" guide?

Ben

 

[onlymeeee]

rotary switches have a stopper in them. Unscrew it and you'll see a round ring with a clip that you can put into any hole you want making a 6 position become 2,3,4,5 or 6.

So you'll want position 4 or however many ratios you are going to do.

Are you going to use 'gain reduction off' (bypass) on another switch? Or have you got an attack pot with a switch like original?

2 sets of wires.. one for the meter (x and y) and then one set for a light

 

[btproductionsaustralia]

rotary switches have a stopper in them. Unscrew it and you'll see a round ring with a clip that you can put into any hole you want making a 6 position become 2,3,4,5 or 6.

So you'll want position 4 or however many ratios you are going to do.

Are you going to use 'gain reduction off' (bypass) on another switch? Or have you got an attack pot with a switch like original?

2 sets of wires.. one for the meter (x and y) and then one set for a light

Great thanks!!
The bypass is on the meter pcb, bypass, GR, VU... I think...

 

[mokkinger]

hi guys, could anybody tell me if i should put in the lundahl input transformer 1:1 or better 2:1?
and what about the output transformer... this one should be 2:1, right?

thanks guys!
mark

 

[alexc]

Hi - I just finished a dual g1176. I tried a number of different IP transformers.
1:2, 1:1 and finally 2:1 (OEPs)

The 2:1 config gave me the most control over the amount of gain reduction I could
get. At 1:1 and 1:2, I found that I had to have the input knob too low to dial in
lower amount of gain reduction. Meaning that more gain make up had to be applied
resulting in more noise overall.

So - 2:1 input from my point of view.

BTW - this unit sounds great. Really great.

 

[gswan]

Just as a side note, on the original 1176LN circuit there is a symbol marked "UA4706 T&C" on the ratio switch assembly.

Given its location, I'd say this is a resistor selected to set the GR threshold to a nominal value setting on the input knob (say 12 o'clock). It's probably selected at 20:1 using a decade box, and then the appropriate resistor value inserted. This would have to be changed if the GR FET was ever changed.

- Geoff

 

[mokkinger]

ok, so 2:1 is you advice for the input...  what about the output?

I have lundahl transformers, should i go for the 2:1?

thanks,
Mark