[BUILD] 1176 Rev A - Back to the beginning...

[sage]

Thank you Swimslowly !
(by the way your builds look INCREDIBLE!)

It really helps to get great advice from pros - today i feel like i have learned something new... now on I will know how to match Fets or at least the HFE in fets... are there other values to match?

This forum has been incredibly useful -

For this built Dave from Cinemag sold me the input and output transformers he suggested - I went to his great Canoga Park location and he is just the nicest - he had me change R4 to a different value - the input is:

CMLI-15/15BTB and for Output: CM-96731

I have no idea how to wire them yet but I am still waiting for the Box from Hairball so still little ways to go...

sage

 

[mnats]

obviously the 460 and 463 are the closest - is this considered a MATCH or they have to be EXACT ? In other words is that a tolerance of percentage in Matching like there's tolerance in resistors' values or they have to be dead on matched?

The tolerance for matching Q12 and Q13 is shown on the original schematic and in the text of my Rev A page.

I would not expect matching to change the sound of the unit either since the matched transistors are in the meter circuit.

 

[MarsonAudio]

Hi everybody, this is my first post so.. please don't be too hard on me
I'm trying to build the 1176 blue stripe using the 1176 REV A 125 pcb board and I have the Cinemag CM-96731 (or PA-96731 since Cinemag built them for Purple Audio as well) output transformer and I was wondering if somebody knows if the wire coloring for this particular transformer matches the one printed on the pcb board. I'm kinda stuck and I can't find any related information online...

Any suggestion would be a terrific help!

Thanx!

Marson

 

[Echo North]

Hi everybody, this is my first post so.. please don't be too hard on me
I'm trying to build the 1176 blue stripe using the 1176 REV A 125 pcb board and I have the Cinemag CM-96731 (or PA-96731 since Cinemag built them for Purple Audio as well) output transformer and I was wondering if somebody knows if the wire coloring for this particular transformer matches the one printed on the pcb board. I'm kinda stuck and I can't find any related information online...

Any suggestion would be a terrific help!

Thanx!

Marson

I'm 99.9999999% sure they have the same color coding.

 

[sage]

Hello

I am actually working with Marson on this Rev A projetc - but hey 2 wrongs don't make 1 right....
We definitely need some help with this wiring...

Thank you - we will follow the guidelines for the same color coding and keep our fingers crossed...

NOW for the Line Input Tranformer can anyone tell me if this is right:

Cinemag CMLI-15/15B :

in:
RED XLR Pin 2 +
BROWN XLR Pin 3-

WHITE - GROUND

out:
Yellow +
Orange -



here the link to cinemag: http://cinemag.biz/line_input/line_input.php

sage

 

[sage]

Just to add to the previous post:

WHITE and BLACK from Input Transformer don't go anywhere right?

sage

 

[Harpo]

Just to add to the previous post:

WHITE and BLACK from Input Transformer don't go anywhere right?

White connects to chassis+XLR-pin1,
black+orange connect to 0V reference voltage, shown as the upside down christmas tree symbol on pcb.

 

[sage]

Harpo are you sure? this sounds strange cause ou of the INPUT Tran we  have :

WHITE
BLACK
ORANGE
YELLOW
RED
BROWN

as at right now I have:

BROWN-RED to INPUT on T-Attenuator
YELLOW to Input + of board
ORANGE to Input - of board

what i have left out is WHITE and BLACK

the INPUT Transformer is CINEMAGCMLI-1515BTB

 

[Harpo]

Harpo are you sure? this sounds strange cause ou of the INPUT Tran we  have :

WHITE
BLACK
ORANGE
YELLOW
RED
BROWN

as at right now I have:

BROWN-RED to INPUT on T-Attenuator
YELLOW to Input + of board
ORANGE to Input - of board

what i have left out is WHITE and BLACK

the INPUT Transformer is CINEMAGCMLI-1515BTB

Dunno what's so strange about it ...
1176_Rev_A_input-hookup
Just glued transformer datasheet and schematic together ...

 

[sage]

Yes indeed this is perfect thank you!

this diagram clearifies it all - I spoke to Dave at Cinemag and he suggestes the Black wire to go to Power Transformer Ground, so white cable goes to XLR ground to chassis while black goes to Power ground -

Usually I put a ground wire to each XLR then to star ground but I guess there is no star ground here but 3 indipendent grounds...

Thanx Harpo for your help!

 

[lukidewa]

Hi all
I have problem with my 1176 rev A (MNATS) push button type.
I finished my board and off board connection. When I do a calibration a problem comes. I can do it Q bias like in mnats video. No reaction from VU when 0db 1kHz sine wave inputed to 1176. The condition when calibrating is +4 with 20 ratio. Pad 22 is grounded too.

Anyone can help me, what happen with my 1176? I've spent 3 days to thinking about this.

Here voltage in all transistor (GR Disable)
    Q1            Q2              Q4            Q11   
D    0              5,81V          11,7V        16,92V
S    0              3,99 V        3,82V        -1,94V
G  -1,38V      1,98V        1,73V        -1,26V


    Q3            Q5              Q7            Q8            Q9          Q10
E  5,88V        2,83V          4,63V        15,48V      3,36V      13,14V
C  12,20V      21,5V          14,93V      26,8V        13,32V    26,2V
B  5,25V        2,31V          4,11V        14,72V      2,74V      12,63V

all is VDC.

Many thanks before  .

 

[Echo North]

Hi all
I have problem with my 1176 rev A (MNATS) push button type.
I finished my board and off board connection. When I do a calibration a problem comes. I can do it Q bias like in mnats video. No reaction from VU when 0db 1kHz sine wave inputed to 1176. The condition when calibrating is +4 with 20 ratio. Pad 22 is grounded too.

Anyone can help me, what happen with my 1176? I've spent 3 days to thinking about this.

Here voltage in all transistor (GR Disable)
    Q1            Q2              Q4            Q11   
D    0              5,81V          11,7V        16,92V
S    0              3,99 V        3,82V        -1,94V
G  -1,38V      1,98V        1,73V        -1,26V


    Q3            Q5              Q7            Q8            Q9          Q10
E  5,88V        2,83V          4,63V        15,48V      3,36V      13,14V
C  12,20V      21,5V          14,93V      26,8V        13,32V    26,2V
B  5,25V        2,31V          4,11V        14,72V      2,74V      12,63V

all is VDC.

Many thanks before  .

No reaction in +4 mode?  What is your AC at the output when you're doing the calibration?  Do you have the resistors installed on the meter PCB?

 

[lukidewa]

thx for reply mike.

yes no reaction in +4 mode. The AC signal from the output same with input signal. yes, i was installed resistor in the meter.

 

[Echo North]

So  you see 0dB signal between pin 2-3 of the output?

Connect the meter terminals (big lower ones) directly to pin 2-3 of the output and see if you get a reading.

 

[sage]

you know i had the same problem yesterday and there was a soldering short in the back of the Meter PCB so i would definitely check in the area once you see as Mike said if your meter reads from the XLR Output -

NOW I HAVE DILEMMA:

My build is finish but I am having trouble with the calibration -

R59 Q bias adjust - after setting +1 dB  on the VU as in the instructional video I attempt to adjust R59 but the trim pot only makes the VU meter needle go UP instead of Down... it is a 2k variable, not a multi-turn.

ALSO Q12 and Q13 - not getting Equal Values from those points.... I am afraid something when wrong... where shall I start looking? Any suggestions -

 

[skidmorebay]

Hi all,
I've got a problem with my Rev A 1176. I've been working on it for days, read and re-read relevant parts of the build thread, triple checked my wiring and am still stuck. Maybe someone else has an idea...
The problem is NO COMPRESSION, and the VU meter stays parked at 0db when switched to GR. The zero set pot does nothing for this. The meter does work perfectly on +4 when signal is introduced.

Echo North's thread with Steve-H was very useful in double-checking the basics (around page 74)

Important points are:
"Q" biasing seemed to go correctly
Voltages are very good when compared to Mako's schematic with voltages - all across the pcb EXCEPT in the GR Meter Driver section.
Q11 gate voltage = -1.03V, source voltage = -0.825V, drain = 4.99V 
Q12 base voltage = -0.825V, emitter voltage = -1.45, collector = 2.07V

The problem I am focused on now is that I have 29.9V at the 30V point in the schematic, just before R79. BUT, on the other side of R79 I have 4.99V instead of the 10.5V shown on the schematic with voltages. I am dropping 24.6V over this resistor instead of 19.5 or so as I would expect...if I understand this right.

I've check the resistor, looked for solder bridges, re-flowed, etc, etc.
Do I understand correctly that just before R79 30V is brought in for use by the transistors, and is dropped to 10.5 by R79?  Trying to wrap my head around why throughout the meter driver circuit I have good voltages on the base/gate and source/emitter terminals, but the drain/collector voltages are all low.

I'm throwing in the towel and asking for help. Anyone run into something like this?

 

[sage]

I am stuck as well....

I am getting these readings for the Transistors:

BASE
Q13 • Base -00.7 Emitter -00.7  Collector 00.1
Q12 • Base 0.6    Emitter 00.6  Collector 5.6
Q11 • Base 7.8    Emitter 0        Collector 0.6
Q10 • Base 13.4  Emitter 13.9    Collector 29.4
Q9 • Base 3.1      Emitter 3.7      Collector 13.9
Q8 • Base 16.4    Emitter 17      Collector 29.4
Q7 • Base 4.7      Emitter 5.2      Collector 17
Q5 • Base 2.7      Emitter 3.2      Collector 24.1
Q4 • Base 12.5    Emitter 2.1      Collector  (i can't measure it its' buried under the orange drops...)
Q3 • Base 6.4      Emitter 7        Collector 12.4
Q2 • Base 7        Emitter 2.4      Collector 4.4
Q1 • Base 0        Emitter 0        Collector 0

Then with the top of the capacitors measure:
C25 • 0
C26 • -17.7
C23 • 00.4
C24 • -08.1
C21 • -4
C18 • 0.5
C9 • 0.4
C12 • 0.5
C4 • 0.6
C5 • 0.4
C3 • 1.2
C17 • 0.2

TP10 • 5.6
TP11 • 0

OUTPUT TRANSF:
BROWN • 27.2
WHITE/BLACK • 2.2
RED/WHITE • 2.1
BLACK • 29.4
GREY • 0
PURPLE • 0

so I would appreciate some help if by reading this data anyone could tell me where to start looking...
If I read the schematics with Volatges properly I see that C23 should measure 29.75 V so it seems like I am off right from the start of the current flow....

 

[Echo North]

Hi all,
I've got a problem with my Rev A 1176. I've been working on it for days, read and re-read relevant parts of the build thread, triple checked my wiring and am still stuck. Maybe someone else has an idea...
The problem is NO COMPRESSION, and the VU meter stays parked at 0db when switched to GR. The zero set pot does nothing for this. The meter does work perfectly on +4 when signal is introduced.

Echo North's thread with Steve-H was very useful in double-checking the basics (around page 74)

Important points are:
"Q" biasing seemed to go correctly
Voltages are very good when compared to Mako's schematic with voltages - all across the pcb EXCEPT in the GR Meter Driver section.
Q11 gate voltage = -1.03V, source voltage = -0.825V, drain = 4.99V 
Q12 base voltage = -0.825V, emitter voltage = -1.45, collector = 2.07V

The problem I am focused on now is that I have 29.9V at the 30V point in the schematic, just before R79. BUT, on the other side of R79 I have 4.99V instead of the 10.5V shown on the schematic with voltages. I am dropping 24.6V over this resistor instead of 19.5 or so as I would expect...if I understand this right.

I've check the resistor, looked for solder bridges, re-flowed, etc, etc.
Do I understand correctly that just before R79 30V is brought in for use by the transistors, and is dropped to 10.5 by R79?  Trying to wrap my head around why throughout the meter driver circuit I have good voltages on the base/gate and source/emitter terminals, but the drain/collector voltages are all low.

I'm throwing in the towel and asking for help. Anyone run into something like this?

I'd ignore the meter section for now and focus on the no compression issue.  Have you confirmed by measuring the output that you're not getting compression?

If you're not getting compression check:
With in/out knobs mid way apply a 1khz 0dB signal and adjust the output to 0dB on the output
- that you see ac at pad 22 that starts larger and get's smaller as you move from ratio 20 to 4.
- that you have a negative DC voltage at pad 21 that starts larger and get's smaller as you move from ratio 20 to 4.

Mike

 

[Echo North]

you know i had the same problem yesterday and there was a soldering short in the back of the Meter PCB so i would definitely check in the area once you see as Mike said if your meter reads from the XLR Output -

NOW I HAVE DILEMMA:

My build is finish but I am having trouble with the calibration -

R59 Q bias adjust - after setting +1 dB  on the VU as in the instructional video I attempt to adjust R59 but the trim pot only makes the VU meter needle go UP instead of Down... it is a 2k variable, not a multi-turn.

ALSO Q12 and Q13 - not getting Equal Values from those points.... I am afraid something when wrong... where shall I start looking? Any suggestions -

For setting the qbias try this:

If you have a version with the "off" switch on the attack pot, you can just switch that.  That will ground pad 22.  Feed a 1khz signal into the input at about 0dBu.  You can put your DMM across input xlr pin 2 and 3 and look for 0.775VAC which is about 0dbu.

Now put your DMM across pin 2 and 3 on the output xlr and turn the qbias (in and out knob mid way).  You should see the output moving up or down.  Turn the bias until it gets to the max and doesn't get any higher. 

Then adjust the output knob so you see +11dbu (2.75VAC) at the output.  Now pull the qbias back until you get a 1dbu drop 10dbu (2.45VAC).  That will set you bias.

Mike

 

[Janzoulou]

If you're not getting compression check:
With in/out knobs mid way apply a 1khz 0dB signal and adjust the output to 0dB on the output
- that you see ac at pad 22 that starts larger and get's smaller as you move from ratio 20 to 4.
- that you have a negative DC voltage at pad 21 that starts larger and get's smaller as you move from ratio 20 to 4.

Mike

Hi there! First of all i have to say that this Kit rocks! Thanks to MR Hairball and MNats for sharing and doing such great support!!!

I am building a Dual - REV A Rotary and so fa so good one of the items is all-ready to rock. (drove some vocals/snares/BD yesterday through and was blown away. It feels, sounds and noises as the old ones.  8) )

Here is my question:

On the other one i don´t get any compression. When I move the R-Switch it changes output-gain for short  then goes back to 0. (Checked output also) Meter does the same.

I did as mentioned above in the quote from echo north. (checking pad 22/21) Everything seems fine there, means the switch should work. I checked all resistors. all good here. The voltages seem all to be good also.

No cold solders nor any shorts. Wiring is exactly the same as the working unit.

Sorry for that, maybe, stupid questions, but I am not that good with electronics... :-[ Any help will be appreciated!!

Cheers, Fredi

EDIT: Forgot to mention that there is a little compression in some stages and if i blow the input up I get some compresssion... so calibrating did work. It sounds clean and the I/O level is almost exact like the other one in GR-Bypass.

Working unit:

R4 : 1dB GR
R8 : 3dB GR
R12: 7dB GR
R20: 10dB GR

Not working Unit:

R4 : 0dB GR
R8 : 0dB GR
R12: 0dB GR
R20: 0dB GR

If i boost the input I get everywhere some GR. (every switch-position almost the same)