[BUILD] 1176LN Rev D DIY

[Commander Fluffypants]

Hi there. I bought a kit that someone had already started building. I'm going through it, checking for any issues before doing any more work on it. I'm new to DIY, but I did recently successfully build two VP28's, four Gar 2520's and two Gar 1731's with no issues. I think I can finish this project off, but the toughest part will be verifying the previous guy's work. I found a couple of things that I think I will redo, but I have what is probably a very simple question for you.

There is a transistor, Q6, that needs to get a heat sink. On mine, the previous guy soldered that transistor all the way down on the board. Should I desolder it and lift it up a bit?

Also, where are you guys getting (and what are you now using) the cap for C2 (27pF)?

Thanks

 

[critterkllr]

Calibration steps 1 and 2 are all set.

Gain Reduction Meter Tracking Adjustment

This step sets your meter tracking so if your compressor is compressing by say 10dB, you see -10dB on the meter.

Start by setting your shorting pin back to the “normal position”  which connecting the two pins closest to Q13.  Your meter will most likely drop.  Set it back to zero by using the R71 zero adjust pot on the front panel.  DO NOT touch the null adjust, it was set in the last step.

Set controls as follows.

Input = “24″ mid rotation - ok
Output = “24″ mid rotation - ok
Attack = full CW - ok
Release = full CW - ok
Compression ratio = 20:1 - ok
Meter mode = “GR” - ok

  1) Apply a 1 KHz, 0dBu signal, confirmed with your DMM at pin 2 and 3 of the input XLR (0.775 VAC). - ok
  2) Move your DMM to pin 2 and 3 of the output XLR. - ok
  3) Set output control for 0dBu (0.775 VAC) at the output. - Starting at 11.21V, I have to move the output almost all the way down. It's very hard to get .775VAC. It jumps between .04V and 3.5V just by barely touching it. After around 3 minutes, I was able to get to .792V
  4) Set attack full CCW (off position). ok Set input control for +10dBu (2.44 VAC) at your output XLR. When turning all the way to the right, the highest I can get is 1.99V. Cannot get to 2.44V.
  5)  Turn the attack control ON (Fully CW) and readjust the output level control for “0dBu” if necessary. No dBu drop when going between on and off attack control.
  6) Now lets set the meter to display this 10dBu drop.  When the attack is “off” (full CCW) and you see +10dBu at the output, set the meter to 0 by using the front panel zero adjust trimmer.
  7) When the attack control is “on” (full CW) and you see 0dBu at the output, use R44 to set the meter to -10. R44 does nothing when moved.
  8)  Repeat 6 & 7 until the output drops 10dBu whenever the attack control is turned ON.  This can be a bit tricky.  You’ll want to anticipate how one control will change the other.

 

[Commander Fluffypants]

So... Yeah... About that cap, C2 on the mnats Rev D board, 27pF... Anyone know where I can get one or a good substitute?

 

[critterkllr]

So... Yeah... About that cap, C2 on the mnats Rev D board, 27pF... Anyone know where I can get one or a good substitute?

How about this one?

http://www.mouser.com/ProductDetail/Kemet/C315C270J2G5TA/?qs=sGAEpiMZZMt3KoXD5rJ2Nx4k5VHhAFgpFoz0auOTgps%3d

You can find similar products on Mouser by pressing the checkboxes and selecting show similar.

 

[dbonin]

I'm having some issues with step 3 of the calibration.

1) When I zero the GR meter with no signal, the meter drifts. It will continue to slowly move to the right. I accidentally noticed that if I blow inside the case, the meter jumps far to the left and begins to move back to the right again. It doesn't matter where I blow in the case. This seemed really strange to me.

Found MNATs FAQ that states Q12 and Q13 are very temperature sensitive.

/quote]

critterkllr  - I have never seen a kit react that way to air movement.  Temperature does play a factor in getting the meter to zero perfectly over time (gotta let them warm up before assuming the meter is not zeroed) but no amount of blowing is going to make the meter "jump far to the left" once the unit is warmed up and working normally.  At least that's been my experience.  I agree, that's very strange and likely points to some other issue.  Perhaps not, but hemmmmm.

 

[critterkllr]

I'm having some issues with step 3 of the calibration.

1) When I zero the GR meter with no signal, the meter drifts. It will continue to slowly move to the right. I accidentally noticed that if I blow inside the case, the meter jumps far to the left and begins to move back to the right again. It doesn't matter where I blow in the case. This seemed really strange to me.

Found MNATs FAQ that states Q12 and Q13 are very temperature sensitive.

/quote]

critterkllr  - I have never seen a kit react that way to air movement.  Temperature does play a factor in getting the meter to zero perfectly over time (gotta let them warm up before assuming the meter is not zeroed) but no amount of blowing is going to make the meter "jump far to the left" once the unit is warmed up and working normally.  At least that's been my experience.  I agree, that's very strange and likely points to some other issue.  Perhaps not, but hemmmmm.

I went through and reflowed solder on everything. After resoldering and another cleaning, it doesn't appear to happen like that anymore when I blow on it. So, it would appear I had a couple/few issues and one was fixed by resoldering and cleaning.

Also, the meter doesn't appear to drift to the right like it used to.

 

[critterkllr]

It appears i have the same problem that some others have had, but I can't find a solution. My best guess is that the pcb traces can pretty easily become listen around the multi turn pots. It makes sense since if they aren't flush and pressure is placed on them to turn them, it can push a trace up. Since R44 doesn't appear to do anything, I'm going to manually jump the traces to their next points on the pcb. Keeping my fingers crossed.

 

[Commander Fluffypants]

So... Yeah... About that cap, C2 on the mnats Rev D board, 27pF... Anyone know where I can get one or a good substitute?

How about this one?

http://www.mouser.com/ProductDetail/Kemet/C315C270J2G5TA/?qs=sGAEpiMZZMt3KoXD5rJ2Nx4k5VHhAFgpFoz0auOTgps%3d

You can find similar products on Mouser by pressing the checkboxes and selecting show similar.

Thanks! I did see that, but I wanted confirmation that it would be a suitable substitute.

 

[Commander Fluffypants]

And now another easy question that will probably appear stupid to experienced folks. The person who started building this thing actually melted part of the on/off switch with his soldering iron... couple of melty spots on the plastic... you think that switch is still OK or should I get a new one?

He also did a bit of a sloppy job attaching the leads from the power transformer. What I'd LIKE to do is just cut those wires and restrip them and start over. They'll be a bit short if I do that. Obviously, I can attach some of the same wire to the shortened wires... but, because they are being connected together at the switch, can I connect them to just one length of wire that then goes to the switch? (Setting it up for 120.)

And yes, I've read the power supply instructions and warnings over and over again on all of the instructions. Getting quite an education and enjoying it.

 

[critterkllr]

And now another easy question that will probably appear stupid to experienced folks. The person who started building this thing actually melted part of the on/off switch with his soldering iron... couple of melty spots on the plastic... you think that switch is still OK or should I get a new one?

He also did a bit of a sloppy job attaching the leads from the power transformer. What I'd LIKE to do is just cut those wires and restrip them and start over. They'll be a bit short if I do that. Obviously, I can attach some of the same wire to the shortened wires... but, because they are being connected together at the switch, can I connect them to just one length of wire that then goes to the switch? (Setting it up for 120.)

And yes, I've read the power supply instructions and warnings over and over again on all of the instructions. Getting quite an education and enjoying it.

The switch should be okay, but a quick continuity test with a DMM will do the trick. Just set your DMM to resistance and put it to beep with 0 resistance. If you're using the hairball switch, it basically takes the inner two lugs and either connects the to the top two (closest to the front panel), or the bottom two (closest to the back of the enclosure). Switch it back and forth to verify that it is functioning correctly for each lug.

Can you desolder the wires without cutting them?

 

[Commander Fluffypants]

I did desolder the wires without cutting them, but when I removed the shrink tubing, which was what was done sloppily (it didn't cover the connections all the way) I noticed that the original insulation was melty. It's just sloppy and I want to make it neat. Most of the work done appears OK. He got way ahead on the wiring, though, without fully wiring up the power supply. Also, I noticed that he left about 3/16ths of an inch on all his leads. Any reason for that? I would have expected them to be trimmed down to the solder.

But back to wiring the power supply... it seems that it would be easier to connect one wire (or two if that's the right way) to the switch and get the shrink tubing on there nice and neat and then connect that wire (or those wires) to the wires from the transformer.

Thanks for the help. I know this is not sexy like calibration issues...

 

[critterkllr]

Lol calibration issues are not sexy! It's the most frustrating DIY experience I've had.

It's hard to give advice on the wiring when I can't see it. So, the best I could say is to use your best judgement. Make sure to keep it clean. Make sure you're using the right gauge wires. Keep nothing exposed.

You could also try loosening the toroidal and rotating it to see if it gives you any extra slack.

 

[JuniusRecordingCo]

No, these calibration issues are not sexy at all.

So I ran a little test with a drum loop. With the input set at "24" and the Output at "48," and Attack and Release mid-way on each. I recorded the output for all Ratio settings, and "Attack Off." While processing the audio, the GR meter only responded to the 4:1 setting. I flipped the phase of the "Attack Off" loop and played it simultaneously with the recordings from each ratio setting. This should give me an indication of what signal is being removed by the compressor. I pulled up an instance of Voxengo's SPAN and found:

"Attack Off" alone, phase reversed: -22.6 dB RMS
4:1 and Loop: -71.1 db RMS
8:1 and Loop: -55.4 dB RMS
12:1 and Loop: -50.2 dB RMS
20:1 and Loop: -47.6 db RMS

So, we seem to be getting compression, and increasingly so as the ratio increases (the loops null less and less, indicating more signal was removed at each increasing ratio setting). The meter needle showed some GR when the input is pushed, with the 4:1 ratio requiring the least amount of input. I run out of input gain before the needle starts moving at the 12:1 and 20:1 ratios.

So it's got to be something on the meter board, right? But I'm a little worried about the gain staging, too. Seems like there's an awful lot of gain available at ouput (I've almost always got it turned way down), and compression doesn't start until a lot of input is provided.

The good news is, after switching to 400mA fuses, I haven't blown any yet.

 

[critterkllr]

Okay, so I have an update with some good and some bad. I did get R44 working! I desoldered it again, cleaned up the area with rubbing alcohol, resoldered, cleaned again. Now it does stuff! Alright!

I tested voltage twice today. The first time, Q11 and Q12 both had B voltage at around 6 volts. I let it sitting on for around an hour, came back to test the voltage again and both are right around 9V now. Just like the schematic. Checked all voltages again and they all seem to check out! I can't tell for Q1, but it is D 0V, S 0V, G -1.2V.

I am still having the same problems with calibration step 3. I can't get a -10dB drop using the input and output knobs. It seems like they work differently than the video. It will only lower -4dB with the attack on/off regardless of how far the knobs are moved in either direction. The video instructions say to turn the input knob to the right in order to lower the dB on the GR meter, but it does the opposite. Turning the input knob to the right raises the dB on the GR meter. While testing audio, the input knob does increase volume when moved to the right.

Just in case this is an issue, I did not remove any of the paint from the faceplate near the pots and do not show any continuity between the pot casings and the chassis ground.

I feel like my unit has more gain than others I've heard and most of the usable range in the pots are at 36 and below. In slam mode, I have to keep the input below 36 and the output at the very bottom of it's range. It also seems to have quite a bit less compression than my plugins. But, I haven't checked it again after cleaning the board.

Since all voltages check out, all wiring is good (verified against the manual and ran continuity tests multiple times), the pots are the right values, and audio passes through, I'm completely stumped on where to go next. I really appreciate any help I can get!

EDIT: I don't know if some shifting or movement caused this, but the resistance between some of the grounded components is no longer zero ohms. The grounded lug at the OT with the board ground is now 29 ohms to the chassis and the input transformer casing is 130 ohms. I'm going to fix this shortly.
Just fixed it, but nothing changed.

 

[critterkllr]

So it's got to be something on the meter board, right? But I'm a little worried about the gain staging, too. Seems like there's an awful lot of gain available at ouput (I've almost always got it turned way down), and compression doesn't start until a lot of input is provided.

It sounds like we're both experiencing something similar with the gain staging. I have a ton of output and I'm getting a less compression that I expected. I had other issues as well, but I've managed to get through most I think. I'm wondering, I just got my Hairball parts kit last week. I bought the Mouser cart parts last year. Perhaps something is up with a batch of components? Maybe one of the pots?

I've also noticed that the output gain seems to change a lot between 6 and 7 on the release knob. I don't know if this is normal, but it's not like this at all in my plugins.

 

[JuniusRecordingCo]

I bought the kit and Mouser parts August of last year. So, maybe?

Anyway: further testing reveals that all transitors voltages are good, except Q11, Q12, and Q13:

Q#	E Measured	E Target	E %	C Measured	C Target	C %	B Measured	B Target	B %
2	0.54	0.54	100.0%	1.75	1.75	100.0%	1.024	1.05	97.5%
3	1.15	1.15	100.0%	11.43	12.58	90.9%	1.749	1.75	99.9%
14	10.83	12	90.3%	29.29	30	97.6%	11.42	12.58	90.8%
4	0.41	0.46	89.1%	4.4	4.2	104.8%	0.98	1.02	96.1%
5	2.64	2.72	97.1%	24.12	26.18	92.1%	3.17	3.25	97.5%
6	2.11	2.2	95.9%	26.81	28.93	92.7%	2.65	2.72	97.4%
11	-0.78			-0.86	-0.9	95.6%	4.61	10.56	43.7%
12	-1.46	-1.52	96.1%	1.89	9.28	20.4%	-0.85	-0.9	94.4%
13	-1.48	-1.63	90.8%	5.35	9.75	54.9%	-0.95	-1.04	91.3%
7	3.84	4.02	95.5%	14.57	15.25	95.5%	4.38	4.54	96.5%
8	13.95	14.7	94.9%	29.29	30	97.6%	14.57	15.25	95.5%
9	2.81	2.96	94.9%	16.5	17.07	96.7%	3.37	3.5	96.3%
10	15.95	16.53	96.5%	29.29	30	97.6%	16.5	17.07	96.7%

I'm not experienced (at all), but looking at the schematic, it seems like Q11 is being fed DC through R79. I pulled it out to measure, and the dang thing is dead. I don't have any 15k resistors handy--but I do have two 33k. In parallel, they'll be 16.5k. Ima gonna try that.

 

[dbonin]

So it's got to be something on the meter board, right? But I'm a little worried about the gain staging, too. Seems like there's an awful lot of gain available at ouput (I've almost always got it turned way down), and compression doesn't start until a lot of input is provided.

I've also noticed that the output gain seems to change a lot between 6 and 7 on the release knob. I don't know if this is normal, but it's not like this at all in my plugins.

make sure you have the correct pots for output and release - moving  the release knob should not change output voltage - after changing release, the output voltage should settle (after a few seconds)  to about the SAME value whether fully cw or ccw.

 

[dbonin]

I bought the kit and Mouser parts August of last year. So, maybe?

Anyway: further testing reveals that all transitors voltages are good, except Q11, Q12, and Q13:

Q#	E Measured	E Target	E %	C Measured	C Target	C %	B Measured	B Target	B %
2	0.54	0.54	100.0%	1.75	1.75	100.0%	1.024	1.05	97.5%
3	1.15	1.15	100.0%	11.43	12.58	90.9%	1.749	1.75	99.9%
14	10.83	12	90.3%	29.29	30	97.6%	11.42	12.58	90.8%
4	0.41	0.46	89.1%	4.4	4.2	104.8%	0.98	1.02	96.1%
5	2.64	2.72	97.1%	24.12	26.18	92.1%	3.17	3.25	97.5%
6	2.11	2.2	95.9%	26.81	28.93	92.7%	2.65	2.72	97.4%
11	-0.78			-0.86	-0.9	95.6%	4.61	10.56	43.7%
12	-1.46	-1.52	96.1%	1.89	9.28	20.4%	-0.85	-0.9	94.4%
13	-1.48	-1.63	90.8%	5.35	9.75	54.9%	-0.95	-1.04	91.3%
7	3.84	4.02	95.5%	14.57	15.25	95.5%	4.38	4.54	96.5%
8	13.95	14.7	94.9%	29.29	30	97.6%	14.57	15.25	95.5%
9	2.81	2.96	94.9%	16.5	17.07	96.7%	3.37	3.5	96.3%
10	15.95	16.53	96.5%	29.29	30	97.6%	16.5	17.07	96.7%

I'm not experienced (at all), but looking at the schematic, it seems like Q11 is being fed DC through R79. I pulled it out to measure, and the dang thing is dead. I don't have any 15k resistors handy--but I do have two 33k. In parallel, they'll be 16.5k. Ima gonna try that.

I suspect something else...  if not, yours is the first "dead" resistor I've head of in years (that wasn't burnt to a crisp first!).

 

[JuniusRecordingCo]

Yeah. A "dead" resistor does seem suspect--I'v never seen one. But this thing, pulled from the circuit, doesn't read at all on my DMM....

...of, course, until I try it again right now. 14.99k. Jeez. I suppose I'll put it back.

So, yeah, it's something else. But what?

 

[critterkllr]

I bought the kit and Mouser parts August of last year. So, maybe?

Anyway: further testing reveals that all transitors voltages are good, except Q11, Q12, and Q13:

Q#	E Measured	E Target	E %	C Measured	C Target	C %	B Measured	B Target	B %
2	0.54	0.54	100.0%	1.75	1.75	100.0%	1.024	1.05	97.5%
3	1.15	1.15	100.0%	11.43	12.58	90.9%	1.749	1.75	99.9%
14	10.83	12	90.3%	29.29	30	97.6%	11.42	12.58	90.8%
4	0.41	0.46	89.1%	4.4	4.2	104.8%	0.98	1.02	96.1%
5	2.64	2.72	97.1%	24.12	26.18	92.1%	3.17	3.25	97.5%
6	2.11	2.2	95.9%	26.81	28.93	92.7%	2.65	2.72	97.4%
11	-0.78			-0.86	-0.9	95.6%	4.61	10.56	43.7%
12	-1.46	-1.52	96.1%	1.89	9.28	20.4%	-0.85	-0.9	94.4%
13	-1.48	-1.63	90.8%	5.35	9.75	54.9%	-0.95	-1.04	91.3%
7	3.84	4.02	95.5%	14.57	15.25	95.5%	4.38	4.54	96.5%
8	13.95	14.7	94.9%	29.29	30	97.6%	14.57	15.25	95.5%
9	2.81	2.96	94.9%	16.5	17.07	96.7%	3.37	3.5	96.3%
10	15.95	16.53	96.5%	29.29	30	97.6%	16.5	17.07	96.7%

I'm not experienced (at all), but looking at the schematic, it seems like Q11 is being fed DC through R79. I pulled it out to measure, and the dang thing is dead. I don't have any 15k resistors handy--but I do have two 33k. In parallel, they'll be 16.5k. Ima gonna try that.

Wild. Well, make sure you are measuring voltages in GR mode. That will change Q12 and Q13.

I also bought my mouser kit in August of last year.