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

[Bonke]

The trimresistors are oriented right. About the operation of the pot maybe you are in the end of its range so nothing more happens when you turn. Have you tried turning it in the other direction to see if anything happens? Or better, do you have another pot to compare with?

Henrik

 

[bieckmusic]

I don't have another trim resistor, but the meter indicator says it's fine?  I've tried turns in both directions and no change, it's so strange...

 

[Bonke]

These multiturns are quite easy to beak. You are supposed to be able to have around 2Kohms between one outer leg and the middle. And when turning there should decrease and you should get around 2kohms between the other outer leg and the middle one. If you can get that your pot is ok.

Henrik

 

[Rellister]

It works. Im amazed. Didnt think I could pull it off 1st try
Passes audio, compresses, all good.
Thanks to Mnats, Mike & others who helped out here!

Love it so far! A couple of minor issues, maybe its normal;

Zero on GR meter drifts abit. Thought maybe I read some other posts about it but couldn´t find them again.
Didnt use the 0 set panel mount pot, just a normal trimpot. Maybe this drifts abit with temperature in the circuit?
Think theres a reason for the panel mount, guess I will be needing it later when the hood is on...
After calibration everything was super but after about 15min of testing the meter started to drift a little.
And - if i turn the output pot to about 9, theres a loud "pop" and some extra noise sets in.
No biggie though, never think I will use it on those levels. It may be normal too. My skills are limited, thought i just put these qs out there.

Thanks guys!
Rune

 

[MicDaddy]

Rellister 

Some things that helped with my meter 'drift'

Let it 'burn-in' for a good while, leave it on over night.  Some folks go so far to pass audio through it all night but that might not be necessary for the meter..

Once it has burnt in for a bit, NOW do ALL calibrations again.  You may find that only minor tweaks need be made, once I did this my meter sits right at zero all day and night. 

Another thing I noticed about the meter, when I have it plugged into the same AC circuit as certain other appliances, it won't sit exactly on zero.  Maybe too much V drop?  Dunno for sure, but do let it burn and then try recalibrating.

One thing to note with my very minor meter drift is that the needle never stepped outside of +/- 1dB either direction.

I've also seen the UA 2-1176 meters do some drifting so it may be inherent with the design.

 

[bieckmusic]

Hello friends, Thanks for the suggestions with the q-bias pot.  I took it out and re-installed it and it seems to be working.  I'm able to now get a dip when I do the q-bias calibration.  However, in GR mode the meter still stays at the bottom no matter if I move the 0 set pot, or other pots...

However, unfortunately now the unit sounds crazy.  Very loud spikes when I move the input gain or output gain, and also when I push ratio buttons.  Is it possible to ruin a transistor or something by accidentally shorting the board?  When I was using the unit before all of the ratios and knobs were working perfectly just not the GR meter???

If anyone has the test points and voltages that should show up there, I might try that next... 

Also in the wiring diagram it says take the yellow wire from the ratio board, but I didn't see a yellow wire in the wiring pages on the ratio board connector...
any help would be appreciated, I was so so close...
thanks! greg

 

[Rellister]

Micdaddy,

Left the unit on overnight and recalibrated.
Taking it down to the studio for some more testing tomorrow, hopefully meter will be fine.
It also seem to drift some between different ratios.
Will report back after some more testing!
Have to take it outside to -15°C (5°F) for a while, hope that´s within spec

thanks
Rune

 

[Rellister]

bieck,

without actually knowing what I´m talking about, just trying to help;

When you set the q-bias, did you take notice of mnats´ error correction in the text before the calibration video?
"In fact, you want to turn the trimmer so that the wiper is in the opposite position or furthest from ground". By reading your trimpots datasheet and comparing to the schematic you should be able to figure out which way is correct. Then, your´re 100% sure your q-bias is correct when you get the drop.

Check continuity between your meter board connections and everything else, sounds like something is fishy in your connections since theres no response from your GR meter.

Good luck
Rune

 

[bieckmusic]

Hi Rune and everybody,

Well, I spent the day yesterday going over the schematic and checking values and continuity for the Meter Driver Circuit.  I couldn't find any shorts or bad wiring hookups.  I still don't have the unit working properly.  Can't get to the bottom of it.  ???

When I put the Q-Bias control to the right spot, then I apply a 1k 0db tone the meter is pegged off the board when the output is 3/4's.  I need to Bring the output really low down to about 9 oclock to get the beter in +4 mode to come down off the top of the range.  Same with the input.

Audio wise, when I have signal going through the compressor it sounds pretty darn good.  The meter indications are pretty far off though.  The input knob is strange sometimes i turn it up and the meter signal goes down first then goes up in +4 mode???

I'm getting the gain reduction to dip a little now and show signs of compression.  It wont go up to 0 though it dips down from about -15???

I checked the trimmer pots, and most of the resistors and caps in the GR circuit.  I don't have a way or know how to check transistors though? 

When the q-bias is set full away from ground the unit is incredibly hot (as in loud volume, I have to bring the in and out pots way down or else I see pegging meters even with no input signal) is this right?

any troubleshooting directing to go in would be majorly appreciated.  The unit sounds so good otherwise, I might just unplug the meter 

thanks so much!

bless, greg

 

[Adam Smith]

I finished building mine last week. Thanks to the excellent build docs, I fired her up and she worked perfectly, first try. That is a first for me. Like many have posted here, I found I had to let it cook overnight before the meter would settle down. I took the unit into work and A/B'd it against the 70's UR*I 1176's there. My Rev A actually sounded better than one of the vintage units and was comparable to the other two. Thanks a ton to Gyraf, mnats, hairball and Ed Anderson for making such an excellent project.

 

[AudioguyII]

First Off... thx to everyone for all the great info.

I've built 2 of these awesome units with exact same components, but am noticing one is fuller in the low mids and the other is brighter....

would love to get a the warmth of one and the top of the other..... could this be due to the calibration?

thx so much in advance

 

[bieckmusic]

Well, just an update.    My 1176 GR meter circuit was not working at all.  So I troubleshooted the circuit for days and couldn't find anything.  Fortunately, I asked two good friends who were electric circuit experts and they said I had some cold solder joints.  My solder iron had the wrong tip, it was way too thick and it wasn't reaching the solder pad. 

Anyway we spent a couple of hours and fixed the joints and the GR meter is now working perfectly!    I'm definitely getting a new iron with adjustable temperature.  Also, I was using two thick a diameter solder.

Everything is working well except I notice the compressor off switch on the attack pot is not working.  I'm so close...
I think I must have wired it incorrectly.

Anyway, this is the first thing I've ever built and it's teaching me quite a bit about trouble shooting and reading schematics.  Very cool!  I'm kind of glad that it didn't work perfectly on the first try because it made me study the circuit.

Thanks everyone for the great, great project!  it sounds so good on guitars! 
bless, greg

 

[Adam Smith]

I've had a couple of problems come up on my Rev A that I'm trying to sort out.

1. It keeps popping fuses. I searched the forum and found that toroidals have a high inrush of current on startup so I upped my fuse to 330mA. It still popped those. I pulled the transformer and tested it with an ohmmeter, no shorts or opens on any of the windings, so I hooked it up to the wall and I'm still getting the correct voltages on the secondaries, the transformer isn't getting warm ect. So, unless there is something I'm missing, the transformer is good. I want to up the fuse to .5A. Are there any components on the PCB that could be damaged by this much current?

2. With the output knob around the 8 or 9 the unit makes loud white noise. It's not gradual, it's more like, you're cranking up the gain and then at one specific point and BAM! super loud white noise. I'm thinking it is a problem in my signal line amp, but I'm not sure where to start. Has anyone else had this problem? Sorry if it has been covered, I couldn't find anything w/ the search function.

any insight would be appreciated.

 

[MicDaddy]

Adam,

from my (limited) experience with this compressor (limiting amplifier) the white noise you hear with the output/makeup at 9 o'clock is typical.  In a typical gain setup I don't know if I've ever pushed the output past 12.  Just my experience, I could be wrong and there may be something wrong with both of ours. 

Are you finding that you need the makeup pushed to that level for a proper signal or is this just from tinkering observations?  (my outboard mixer, (Dynacord) gets really noisy that last 10dB of gain) It'll be super clean for dynamics and ribbons gradually upping the level and then right when I get to that 60dB WHOOSH there it is, instantly really super hot and white noise.

 

[Rellister]

Adam,

from my (limited) experience with this compressor (limiting amplifier) the white noise you hear with the output/makeup at 9 o'clock is typical.  

Happened to me too. Seems normal.
Bieck - glad to hear you´re up and running. I´m surprised there´s not more fuzz about this revision, it sounds great!

And yeah - about the GR meter drift.
Mine settles fine at zero after i turn it on. During the next few minutes it slowly rises to +1.
tried "burning in" and recalibrating.

As I said before, no biggie, just irritating. Could it be transistors in meter circuit not being matched properly?

EDIT - Adam, you´re using slow-blows?


Cheers
Rune

 

[Adam Smith]

Adam, you´re using slow-blows?


Cheers
Rune

Yeah. Slow-blows indeed. I upped the fuse to .5A and now I'm having no problems. Weird thing was, I took the transformer out of circuit one connection at a time to track down any shorts that might have been causing the problem, once I unhooked it from the pushbutton switch, the 250mA fuse was fine. I saw in the Rev D thread people were having the same problem when switching from rotary to pushbutton.

And just out out of curiosity, is there a practical way to measure the inrush current draw?

 

[bieckmusic]

Thanks Rune!  When I power up, the gr meter starts at -1, then it slowly climbs up over the next hour to -.5.  Oh well, I', going to live with it.

Gotta say, this thing sounds so good.  I built it with the stock parts from the BOM.  I really want to try building another one with Carbon Comp resistors and maybe some expensive "old school" transformers just to see the difference.  My unit is bright, with lots of tasty, and crispy highs from 5k to 12k.  The low end is nice but sounds slightly cut from about 300hz down.  I think it's great because I built it for acoustic guitars and it does a really nice thing to the sound.  I'm wondering if carbon comp resistors and different transformers would give me some more low end for snare?

I read of a company called jupiter that makes vintage capacitors.  I'm gonna try them in my drip opto4.  Maybe I'll try some in the 1176 for fun. 

best, greg

 

[Rellister]

Don´t know what other transformers would do to the sound, but  Ben made a thread where he experimented with different components, really helpful, thanks ben!

http://www.groupdiy.com/index.php?topic=40154.0

Seems like transistors affect sound more than other things. To me the 3708 are "bright" enough.

Regarding resistors, I really dont know how they affect sound, if they do at all. Someone correct me if I´m wrong. Of course no harm in experimenting

Slightly cut from 300Hz down? Sounds strange, that would mean a real lack of low end. Did you check your frequency response through the unit?

 

[evilcat]

Don´t know what other transformers would do to the sound, but  Ben made a thread where he experimented with different components, really helpful, thanks ben!

http://www.groupdiy.com/index.php?topic=40154.0

Seems like transistors affect sound more than other things. To me the 3708 are "bright" enough.

Regarding resistors, I really dont know how they affect sound, if they do at all. Someone correct me if I´m wrong. Of course no harm in experimenting

Slightly cut from 300Hz down? Sounds strange, that would mean a real lack of low end. Did you check your frequency response through the unit?

You're welcome, man ! I'm glad to bring some contribution to this forum. As a newbie, I can't do much more !

 

[SmitH]

I've been trying to Calibrate my 1176A for weeks.
It passes audio, doesn't soundlike its compressing though, all i can tell is the level drops when the rtion is switched to 20.
With 0.775v 1K input signal, I can't get the meter to go above -10.
The Q-bias pot will only move the meter from zero to -10.

Re-checked the wiring 20 times. Seems to be correct.

I've used the 2N5088's with the alternate base pad.
Q9 and Q7 are measuring 0.2v across Base-Emitter junction, whereas Q10 and Q8 are measuring 0.6v
Is this normal?