[BUILD] 1176 Rev F/G - new board, new transformer!

[Kimmosavilampi]

I noticed that i get continuity between the  output - and + on the output of the Altran C3837-1 .. Should this happen? Maybe this is the issue of no sound or life shown in the meter?..or maybe i should set the trimpots halfway up and try again to see if it gives anything.. very wierd..

If i read the Schematic right..they should have continuity?

 

[Kimmosavilampi]

Another factor that me does not work is to put the switch of attack in off. I put the pin 22 to ground, but the VU meter not decibels decreased (gain reduction to put calibration). I have checked the unit...

Hi,

I'm not sure what you mean exactly, but have you wired your switch for the GR off/on as in this diagram from Skylar?

Could i get a picture like this on the Rev F? would be godsent for me..i have some Ratio + Meter  circuit issues on my Rev F

 

[Kimmosavilampi]

I Have become somewhat wiser now,

Regarding my issue = GR Meter Shows sign of life when putting 1176 on. VU Meter reacts to turns on the Zero Adj pot, And reacts to trim pot for Tracking Adjustment.So this is okay (i think?)

When i switch Meter to +4 it drops down to 0 (as it should? )

i Set the ratio to 4:1,
Attack/Compression OFF, (Full CCW)
Release on 7 (full CW)
Output pot to 3/4 (or full CW sometimes),
Set an input signal from XLR, (1khz, 0 db sinewave (loud),

I turn the T-POT/Input volume CW


Nothing happens..no sign of life..


When 1176 shutdown:

I get a signal from XLR->to->T-POT->INPUT TRANSFORMER->PCB "+ & -", i get a weak sound when putting my old headphones to those pads (wires if you use the terminal blocks)

So there is audio coming trough and get attenuated by the T-POT and gets trough the transformer.


Now,


I have measured the Transistors, as shown in this troubleshooting Guide for Steady-state DC bias conditions here,

http://www.axtsystems.com/index.php?option=com_content&view=article&id=57:1176lnproblems&catid=34:1176ln&Itemid=62

i used the spreadsheet as a reference (i hope this is a correct reference for the Rev F ?)


And i see some differences on the placement on B, C, E Values on some transistors...is this normal? for example: instead of

On the spread sheet
2N2925 = Q5 B=4.88  C=28.3  E=4.40                            0,48 V idle running
2N5087 = Q6 : B=28.3  C=14.4  E=28.9                            0,6 V  idle running

My Values

2N2925  = Q5  B= 3,1  C= 27,5  E=3,4        = B-E        0,3  Volt on idle running ??
2N5087  = Q6 B= 28,1 C= 27,5, E=16,0      = B-E        12,2 Volt on idle running ??



It is after Q4 things start to look wierd..

Have i put the legs wrong on some of these transistors? I checked the picture in the beginning of this whole thread and they look exactly how i have soldered them?..i really really hope ive not made a mistake here,

ALTOUGH the picture  in the beginning of this thread is a V 1.1



Is this where i have my issue for the ratio not showing any sign of life?..


Any help would be appreciated..i feel very confused right now..the input should not be a problem though..i think ??



Thank in advance,


//Kimmo

 

[Kimmosavilampi]

Hi again,


I seem to be the only one alive here,


I succesfully get a signal through my 1176 now! i had wired the GRY, GRN, VIO, BLU wrong in the output, AND the hot & negative.

Rookie mistake.


Anyhow.


Im trying to follow the Q-bias video from Don Bonin, but i realized something..the video from Mnats & Dan Bonin(youtube) is done on the REV D.


The Q-Bias trimmer which has its front to the left on the REV F (and REV D) should lower the peg turning the screw CCW... but mine just gets more open doing that? I took my multimeter and measured the ohm and i found that CCW gives higher ohm, CW makes the ohm go to about 2ohm...


Mnats v.1.1 has the Q-bias & Tracking Trim the oppisite way..maybe this is a default on the REV F PCB? I have a hard time to tell..because as i said, mine works backwards. Makes it hard to do bias correctly (altough its just reversed and should not matter, you just need the middle pin to be in the middle)


Anybody had this same "issue" ?


Ive measured every transistor and the voltage values are as following:


Q1=N/A
Q2=    1.0        1,8      0,5    = 0.5V
Q3=    1,2        11,3    1,8    = 0.6V
Q4=    11,3      29,5    10,7  = 0.4 V ?
Q5=    3,1        27,5    3,4    = 0.3V ?
Q6=    28,1      27,5    3,4    = NPN transistor?
Q7=    28,7      16,0    28,1  = 0.6V
Q8=    16,0      29,3    15,4  = 0.6V
Q9=    14,7      0        15,3  = 0.6V
Q10=  N/A
Q11=  N/A
Q12=  4,4        14,6    3,9  = 0.5V
Q13=  14,6      29,3    14,0  = 0.6V
Q14=  3,4        16,7    2,8    = 0.6V
Q15=  16,2      29,3    16,1  = 0.1V ?


I followed the troubleshooting spreadsheet from axtsystems.com 

http://www.axtsystems.com/index.php?option=com_content&view=article&id=57:1176lnproblems&catid=34:1176ln&Itemid=62



I saw 2 Q´s with a wierd voltage value...maybe that depends on the transistor treshold values but.

I am talking about Q4, Q5, Q15


So are my transistors alright?


/Kimmo

 

[Echo North]

I noticed that i get continuity between the  output - and + on the output of the Altran C3837-1 .. Should this happen? Maybe this is the issue of no sound or life shown in the meter?..or maybe i should set the trimpots halfway up and try again to see if it gives anything.. very wierd..

Yes that is normal.  The DC resistance for that transformer is VERY low.

 

[dmnieto]

Very stupid question. Isn't the capactior C26 in the picture that opens the thread mounted wrongly? Silkscreen shows the positive lead of C26 on ground, but in the picture it is the negative!

Now, that would explain why C26 in the picture is damaged (top of the capacitor bumped)

 

[Hiflygunther]

Hello , i just finished my Rev F, all seems to word fine, but i have a little question....
It seems that my attack knob is reversed...knob near off, short attack and knob at 7 long...i check the wiring again and all seems to be as it should...Do you have an idea why i have this feeling/problem...perhaps im wrong and it s normal but i doubt...Should i just rewire it reverse ?
Thanks a lot

 

[Hiflygunther]

Ok, my fault, i change the wiring and all seems to be ok!
I Will make a lot of test in the studio, and i hope i ll not come back with silly questions!

 

[hymentoptera]

Very stupid question. Isn't the capactior C26 in the picture that opens the thread mounted wrongly? Silkscreen shows the positive lead of C26 on ground, but in the picture it is the negative!

Now, that would explain why C26 in the picture is damaged (top of the capacitor bumped)

This is a very good point. I'm looking at a Rev F PCB right in front of me, and the capacitor C26 in the photo in #1 OP first post of this thread is apparently installed backwards. 

 

[dmnieto]

Ok I finished wiring the 1176 and it sounds quite nice...

I only see a problem. Every time I power the unit, it seems to lose its GR "zero-tracking" callibration, as it drifts by around 1dB to the left when no signal is applied.

I re-calibrate, and when I power again it does it again.

Any ideas of what could be the issue?

Could it be an issue with C28? it would be weird, but I had to change it for a different 0.1uF capacitor I had around because I blindly ordered hairball's mouser cart without checking that the WIMA capacitors were of 1uF value.

 

[hymentoptera]

Ok I finished wiring the 1176 and it sounds quite nice...

I only see a problem. Every time I power the unit, it seems to lose its GR "zero-tracking" callibration, as it drifts by around 1dB to the left when no signal is applied.

I re-calibrate, and when I power again it does it again.

Any ideas of what could be the issue?

Could it be an issue with C28? it would be weird, but I had to change it for a different 0.1uF capacitor I had around because I blindly ordered hairball's mouser cart without checking that the WIMA capacitors were of 1uF value.

does it eventually return to zero after warming up for 10 or 15 minutes?

 

[dmnieto]

Didn't test it, but it does not look like it for a while.

Also, other things:

1. My mouser cart came with two kinds of 0.22uF (WIMA and KEMET) which ones do you recommend (the start of the thread commented the WIMA were transient killers).
2. I turned the Q bias all they way to the wrong side before doing the calibration, I powered the unit and when I realized my mistake I put the potentiometer over to the other side and did the callibration.
The weird part is that since then, it does not seem that I can reliably measure resistance on the potentiometers on the lower part of the circuit... (like some quiescent charge being stored somewhre and discharging when I try to measure)... do you think I damaged something.?
3. It seems like the circuit has a somehow strong 3rd order harmonics, I am not getting 0.07 THD for 0dB output 1KHz, but more about 0.18. Any ideas?

 

[hymentoptera]

Didn't test it, but it does not look like it for a while.

Also, other things:

1. My mouser cart came with two kinds of 0.22uF (WIMA and KEMET) which ones do you recommend (the start of the thread commented the WIMA were transient killers).

I've read that 1176's were transient killers ;D but seriously, I think people are putting WIMAs in both positions beacuse the EVOX doesn't fit (v1.2 board in front of me), leads are too wide. We had this problem with the Rev A and the guys changed the BOM to a WIMA. Note that C5 and C2 screenprint labels are swapped on v1.2 PCB, so C5 is really labelled C2..

2. I turned the Q bias all they way to the wrong side before doing the calibration, I powered the unit and when I realized my mistake I put the potentiometer over to the other side and did the callibration.
The weird part is that since then, it does not seem that I can reliably measure resistance on the potentiometers on the lower part of the circuit... (like some quiescent charge being stored somewhre and discharging when I try to measure)... do you think I damaged something.?

You can't reliably measure any resistor in-circuit. You have to desolder at least one leg (possibly two on a potentiometer). What you are seeing is a capacitor charging/discharging. This is kinda typical of trying to measure a resistor in-circuit.

3. It seems like the circuit has a somehow strong 3rd order harmonics, I am not getting 0.07 THD for 0dB output 1KHz, but more about 0.18. Any ideas?

There should be a lot of distortion of during compression. That's what this box does. But anyways, is this happening with the GR off or only while compressing?

Also, be sure you let the machine idle, chewing on a test tone for at least 30 minutes prior to any testing. These things are alive, and behave differently cold than when hot, especially under the scrutiny of measurement.

 

[dmnieto]

You can't reliably measure any resistor in-circuit. You have to desolder at least one leg (possibly two on a potentiometer). What you are seeing is a capacitor charging/discharging. This is kinda typical of trying to measure a resistor in-circuit.

I had one of those, "oh damn" moments, ignore me

There should be a lot of distortion of during compression. That's what this box does. But anyways, is this happening with the GR off or only while compressing?
Also, be sure you let the machine idle, chewing on a test tone for at least 30 minutes prior to any testing. These things are alive, and behave differently cold than when hot, especially under the scrutiny of measurement.

It happens all the time, the 3rd order harmonic, but I think it is characteristic of the operation of the JFET, the only moment it is not present is when I q bias it out of conduction.


Unfortunately I blew a fuse yesterday while swapping my capacitors... I started to measure much more noise in the audio path and I had quite a lot of amplification. ( The +4 meter was on the red with very low amount of input signal)... and then the fuse died... I am checking a bit more before I take a break today

 

[dmnieto]

Ok, so I finished and repaired my build. Some comments:

- The 3rd harmonic seems to be related with the input transformer, it is added at the beginning of the input chain. I tried demagnetizing it, but still sits at around -70dB with a 0dBu (@600Ohm) with GR disabled.
- I used 5N5089 transistors instead of the 2N3707. They have a bit lower max VCE (25V vs 30V), but I guessed that it would still be ok on normal operation, the advantage is a much higher hfe and lower Nf (2.0dB). They also have a good bandwith-gain.
- The compressor shows an almost flat frequency response (+/- 1dB) on the band from 20-24KHz. Funny enough, there seems to be a dip of around 1dB around 1KHz with slowly rises back to 0dB at 12KHz
- I replaced the WIMA 0.22uF (MKS2) for the Kimet, I agree with Kingston, they have a significant impact in the audio path, but I think I know why.

I measured the attack/release response using pulses of different lengths/voltages. There is a quite considerable difference in the shape of the the curves for different transistor/capacitor combinations, also there is a difference in the shape of the harmonics when compressing a sinusoid.

The pairing 2N3707/WIMA shows attack/release responses that look a bit like a butterworth filter, with no ringing. Also the harmonics where compressing follow a 1/f^2 decay with the odd harmonics being higher than the even harmonics.

The pairing 5N5089/KIMET has attack/release responses that ring a bit (probably 1dB) but interestingly enough when feed with a constant tone and compressing the harmonics neatly follow neatly a 1/f decay.

To my ears 5N5089/KIMET has significant more warmth, probably because of the ringing in the release which appears to be quite pleasant on the transients.

I am going to try to upload sound samples of the different combinations

 

[SonicSonar]

Hello

Can I use the output from mnat PSU,  -10 Volts,  to power the VU meters and Power lamp? 
http://mnats.net/psu.html

 

[hymentoptera]

Ok, so I finished and repaired my build. Some comments:...

I am going to try to upload sound samples of the different combinations

Is this C27 where you're putting the .22uF Kemet? Or C5, or both? I'm still gathering parts for a Rev A, and there is no equivalent for C5 in the Rev A (C9 in Rev D), but all versions have C27 equivalent (same as C22 in Rev A and D).

If C27 is the Kemet and you feel it have such an impact on sound, I will try to experiment with different .22uF caps at C22 in the Rev A.

Would love to hear clips/examples

 

[dmnieto]

Is this C27 where you're putting the .22uF Kemet? Or C5, or both? I'm still gathering parts for a Rev A, and there is no equivalent for C5 in the Rev A (C9 in Rev D), but all versions have C27 equivalent (same as C22 in Rev A and D).

If C27 is the Kemet and you feel it have such an impact on sound, I will try to experiment with different .22uF caps at C22 in the Rev A.

Would love to hear clips/examples

Hey, it is both C5 at C27 as thery're are both part of the feedback chain (take into account there is an error of the schematic in rev G, C27 couples the FET gate to GND), but in my opinion it probably has to be C27 the one that has the biggest impact, so C22 in REV A could have a similar impact.

Examples recorded on same settings (other than changing the caps) judge yourself.
Original sample
2N3707/WIMA
5N5089/KIMET

 

[hymentoptera]

Is this C27 where you're putting the .22uF Kemet? Or C5, or both? I'm still gathering parts for a Rev A, and there is no equivalent for C5 in the Rev A (C9 in Rev D), but all versions have C27 equivalent (same as C22 in Rev A and D).

If C27 is the Kemet and you feel it have such an impact on sound, I will try to experiment with different .22uF caps at C22 in the Rev A.

Would love to hear clips/examples

Hey, it is both C5 at C27 as thery're are both part of the feedback chain (take into account there is an error of the schematic in rev G, C27 couples the FET gate to GND), but in my opinion it probably has to be C27 the one that has the biggest impact, so C22 in REV A could have a similar impact.

Examples recorded on same settings (other than changing the caps) judge yourself.
Original sample
2N3707/WIMA
5N5089/KIMET

They both sound nice really. They're certainly different, but I couldn't say that either sounds "better". Perhaps the WIMA sounds more "compressed", more evened-out from note to note. The Kemet feels smoother. This is most noticable for me at the loud chord at 7s400ms point. I almost feel like the WIMA allowed more of the character to come through.

I'm glad to know it's safe using whatever I choose here, and the differences will be negligible to my ears. Note that I don't believe the Rev A, with it's class A preamp, has the equivalent feedback circuit containing C22, as C22 on the Rev A is the C27 on Revs D/F/G and Rev A's C27 is the 0.12uF (or .012uF or .015uF depending on which BOM or schematic you're going by) capacitor strapped across the attack pot, and I think unrelated to C22 on Revs D/F/G.

Right now I'm thinking of using a Mallory 150 .22uF metallized polyester where Rev D/F/G's C27 is located. My other option I hope to test will be a pile of Sprague 439P rolled mylars still needing measured and sorted.

Did you have to bend the leads to get the Kemets to fit?

 

[dmnieto]

They both sound nice really. They're certainly different, but I couldn't say that either sounds "better". Perhaps the WIMA sounds more "compressed", more evened-out from note to note. The Kemet feels smoother. This is most noticable for me at the loud chord at 7s400ms point. I almost feel like the WIMA allowed more of the character to come through.

I'm glad to know it's safe using whatever I choose here, and the differences will be negligible to my ears. Note that I don't believe the Rev A, with it's class A preamp, has the equivalent feedback circuit containing C22, as C22 on the Rev A is the C27 on Revs D/F/G and Rev A's C27 is the 0.12uF (or .012uF or .015uF depending on which BOM or schematic you're going by) capacitor strapped across the attack pot, and I think unrelated to C22 on Revs D/F/G.

Right now I'm thinking of using a Mallory 150 .22uF metallized polyester where Rev D/F/G's C27 is located. My other option I hope to test will be a pile of Sprague 439P rolled mylars still needing measured and sorted.

Did you have to bend the leads to get the Kemets to fit?

Isn't it the most amazing part that you can change the character with such a small piece? But yes, I believe rev A C22 is the same as C27 in rev D/F, so I would try to play with that one.

You would need to bend the leads unless you build some kind of socket that would allow to adapt it.

I still like more the smoothness of the KIMET one, but it is true that the chord at 7s certainly rings different. If you look at the transient you will see what I was commenting, the KIMET is attacking probably a tight bit faster but it has some ringing, the WIMA is clean there