[BUILD] 1176LN Rev D DIY

[Spadehead]

Hi all, I wonder if someone out there can help?

I built my first rev d compressor a few months back and all seemed to go well. So much so that I bought another one and have just hooked it up. Everything seemed to go ok until I got to calibrating the unit. The first 2 stages of calibration went well but I can't seem to get the 3rd stage sorted as the attack knob doesn't appear to be doing anything. I switch it on and the unit doesn't appear to be applying any gain reduction at all.

I re-checked all the connections and everything seems to be fine but I am kind of at the end of my expertise - if someone could suggest a possible starting point for fault finding that would be great. I know it's a "how long's your piece of string" moment but if anyone else who has had this problem could chime in it would be appreciated. Also some common starting points to check voltages to hopefully narrow down where the error lies would be awesome.

I am very keen to get this unit up and running as I have gotten an enormous amount of use out of the first already and there's a space wanting in the rack!

Best wishes

Ade

 

[Echo North]

If your issue is no gain reduction, check the REV A thread in this forum.  Look at the last page or two where I helped Stitch-o.

Basically it walks you through checking that signal is getting to the GR amp, offset voltage is correct, and the DC values look correct.

 

[PeterL]

Thank you Mnats, I will take some time out this weekend to take readings of all of the transistors and everywhere else on the Rev D schematic you have supplied on your website and post them here to the forum. Hopefully I can get this sorted and learn what I did wrong at the same time. I'm planning on these two Rev D's to be matched, for use as a stereo pair with a link from Hairball.

The popping is coming from the newer unit, which is the louder and brighter of the two, though it only happens when the Attack is between 5.5 and 7 on the faceplate.

 

[Spadehead]

If your issue is no gain reduction, check the REV A thread in this forum.  Look at the last page or two where I helped Stitch-o.

Basically it walks you through checking that signal is getting to the GR amp, offset voltage is correct, and the DC values look correct.

Okay so I'm having a look at this thing fresh this morning - I ran it up with it patched over some drums instead of a tone and found that there is no GR when the ratio switches are pushed in. As soon as I take all the ratio buttons out I get compression!? It sounds to me like it's doing all-button compression when no buttons are pressed. Any one else had this issue?

Ade

 

[Spadehead]

Okay, I'm being an arse.

Figured out I had the cable from the attack pot to the PCB inverted....doh! I must have checked it a dozen times and didn't see it, I swapped it at the PCB and hey presto!

I still struggled with the calibration - I had to work harder than the first time to get the GR calibration step finished but now I have 2 nice units in a rack and they are both remarkably similar level-wise - I just have to up the output a little on the second unit to match the levels. Thanks to all for the help - it just goes to show: patience is the key!!

 

[PeterL]

It's the strangest thing, now neither of my units power on. Oddly, the one I built a month ago and had been using frequently was the first to go. About an hour later, the newer unit went out. They do not power on with known working IEC cables and an inspection of the PCB and other internal parts do not show visible signs of damage or wires that could be shorting the units out. I had these both working friday night, albeit slightly different and one with a problem.

I'm going to backtrack on this thread and see what other people have done when this sort of thing happens, if it has. I haven't checked yet, but I will now.

 

[Echo North]

Blown fuse?

 

[PeterL]

My thoughts too, at first, but no. I forgot to mention that above. Basically, everything seems to appear fine and as they were except the compressors won't power up anymore. Neither fuses are damaged.

 

[Soundmugician]

Since your fuses are ok, next I would check that you are getting 30 volts ac out of the power transformer(s) ( the side of the power transformer that goes into the board ). If that is ok then you can check for the 2 dc voltages on specified points on the board which are around the rectification circuit ( the part with the big capacitors ), it's marked on the board, one voltage is 30 volts dc, i believe and the other is -10 volts dc.

 

[dbonin]

If anyone is looking for some inspiration to get their 1176 finished, I posted a bunch of photos of my finished rev d mnats/hairball build on my website: http://paulmantiniaudio.blogspot.ca/2012/03/and-so-we-continue-our-journey.html
Enjoy!

Beautiful job!  From one canuck to another, keep rockin brother!

 

[PeterL]

Thank you, Soundmugician.

The fuse is norm, known working IEC power cable connected, still both units do not power up. As you suggested, I tried to take a reading of where the power transformer comes to the board, but it zeros out. Same with the two points marked on the PCB for +30 and -10. Actually, touching any connection on the PCB, pots or switch assemblies zeros out the meter. Same for both units. I may try disconnecting some things and working back from the power transformer, after I discharge the capacitors.

 

[sr1200]

Peter, with your meter in AC mode, check the voltage going into your IEC first. (both sides of the fuse)  If your reading is good there, if the reading it good there, remove the transformer from the board and check the leads from the transformer.  If you're getting NOTHING from the transformer, i guess it might be possible the transformer blew, but I would have to think that's a rare occurrence (but does happen).  If you're getting proper voltage from the tranny, time to check the PS and your VR (and caps... are any of them looking a little bulbous or cracked on top?)

 

[safe as milk]

i think this is a first....i have a stereo unit im building/butchering
and with the vu set to gr both needles come up to zero upon turning the power off :'(
i've been tinkering on & off for a week now so was just hoping for somebody to
suggest an area to concentrate on?

also is violet meant to go to ground on the output transformer(cinemag)?

will post transistor voltages in a mo...

thanks as ever

 

[number2]

I did the initial Q bias calibration and everything went well.

However, I tried to do the second calibration and in the process I noticed that I don't have an R71 to adjust and since I attempted this now  my 1176 does not power up any longer.
The meter lamp used to come on and power was verified by voltage tester. Now I get nothing. The fuse looks OK but I don't know.

a little help please

oh I also have this extra  mnats meter and ratio board I don't know what to do with

 

[safe as milk]

first a big thankyou to mnats for these boards from the very 1st batch i believe.
i drilled out those funny pads on Q7-Q10
and mike hairball for all the other bits and pieces

voltages listed C/B/E..........hhhhhhhhmmmmmm

Q1 cant get a reading?
Q2 1.79  / 0.89  /0.56
Q3 12.82/  1.78  /1.18
Q14 31.4  /12.82 /12.4
Q4  7.31/2.52/2.06
Q5 28.3 /0    /0
Q6 cant get a reading but i can inject tone at r33 and get it out
Q11 13.37/0.53/ ?
Q12 11.7/0.66/0.08
Q13 3.49/-0.55/-0.25
Q7  15.39/4.37/4.12
Q8 31.5/15.14/14.96
Q9 15.72/3.56/3.05
Q10 31.5/15.17/17.23

im poking around the line amp, seems a pretty safe bet

cheers

 

[minor_glitch]

Beautiful job!  From one canuck to another, keep rockin brother!

Thanks!

 

[Terge]

On the MNATS site there is a REV D schematic with typical voltages added.  I would check them all in both units.

Mike

I have been looking at that schematic when trying to figure out why my compressor isn't compressing; I''ve gone through step 1 and 2 in the calibration routine but now on step 3 I can't get any gainreduction, nor audible or measurable.

Does calibrating the unit change the voltages over Q12 and Q13? Mine is really nowhere near the ones on the schematic.

Q12: B -.7 C 11.2 E -1.38
Q13: B -.9 C -1.4 E -1.4

Does anybody have any idea what could be causing this? I've resoldered all the transistors and I measured all the resistors before mounting them.

EDIT: Now I've resoldered all of the meter driver and I can actually get some reduction if i slam the input gain to the max, but nowhere near 10dB, I used my DAW for calibration; have I messed something up?

 

[number2]

Will a 0.5 amp slo blo, 250 v fuse work?

 

[safe as milk]

hi
number 2 the docs say-

Insert the appropriate 5 x 20 mm fuse in the fuse holder
- 1/8 Amp Slo-Blo for 120V or 1/16 Amp Slo-Blo for 240V AC line voltage.

i've now narrowed my boards down to funny voltages at the 2n3391a Q4  6.5/2/2
then  Q5 31/0/0  & Q6 0/0/0 !

managed to do the q bias and the null adjust using output pot signal...GR is working well.
but have small distorted output on both my boards.

do Q4 2n3391a have to be selected for hfe?

changed Q4 to bc547...hfe600...no change in voltages.

replaced Q6 no change...

when i disconect either of the wht/red or wht/blk i get most my level back(still distorted)

voltages at Q4 are good when either the grey or violet output transformer wires are disconected

cheers

 

[safe as milk]

i've got dc at the violet & grey output transformer...that can't be good can it ;D