[BUILD] 1176LN Rev D DIY

[jplebre]

Yes when I said above to use the chassis as reference ground, that was because the neg side of C25 had been hooked up to the chassis.
Sorry if it confused matters

 

[jeffroberts]

The negative side of c25 is wired to the chassis. I need to check that its making electrical contact. that ground was the last connection i made and I forgot to check continuity on it

 

[Che_Guitarra]

I'm populating the Mnats 1176 Rev D board as we speak.  I've tried looking through the thread for my answer but it can be a little overwhelming.

Can I get a confirm the R12 (920Ω) is actually supposed to be 1.8KΩ?  Are there any other values printed on the Mnats PCB that I can't copy verbatim?

 

[jeffroberts]

That resistor is the only one I have noticed so far. But Yes, the 920 should Be 1.8k. Also, the board Is labeled For  2n3707 transistors. The transistors included in the mouser Cart provided by hairball are 2n3708, but they will work fine in the Circuit.

 

[Che_Guitarra]

Good to know.  Thanks Jeff

 

[Echo North]

I'm populating the Mnats 1176 Rev D board as we speak.  I've tried looking through the thread for my answer but it can be a little overwhelming.

Can I get a confirm the R12 (920Ω) is actually supposed to be 1.8KΩ?  Are there any other values printed on the Mnats PCB that I can't copy verbatim?

Have you read this?
http://hairballaudio.com/shop/fetguide.php

Note #1:
Visit MNATS.net and find the info page about your build (Rev A and D only). Read through the page so you understand the basics of the circuit and your revision. Check the bottom of the page to see if there are any updates or corrections to components or values on your PCB version.

 

[jplebre]

Can I get a confirm the R12 (920Ω) is actually supposed to be 1.8KΩ?  Are there any other values printed on the Mnats PCB that I can't copy verbatim?

Yes, No. (1n3708 is a direct replacement for 3707 as it's hard to find high hFE values for the GR section)
Mind different pinout if using other transistors in here

[quote author=Che_Guitarra]I've tried looking through the thread for my answer but it can be a little overwhelming.[/quote]
At the top of the page, press "print", then use your browser's search function. Or print as PDF and use your PDF reader search function (Apple+F if you're a macboy like me)
Makes it ultra easy to search

 

[Che_Guitarra]

Thanks guys - I've read all the Mnats and Hairball 1176 links a few times, and basing the component locations on the Hairball/Mnats BOM (http://hairballaudio.com/bom/RevD.pdf).  It's been pretty straight forward so far, the circuit board is pretty much done now, but a few of items seem to be missing.  The 2N5457 FETs for Q1 & Q11 seem to have been overlooked/omitted, a capacitor for C2, and so too a Bourns 2K trim adjuster.  Otherwise it's been a day of fun with the soldering iron 

 

[jplebre]

The 2N5457 FETs for Q1 & Q11 seem to have been overlooked/omitted, a capacitor for C2, and so too a Bourns 2K trim adjuster.  Otherwise it's been a day of fun with the soldering iron 

You should have received them with the kit from Mike (Echo North - Hairball).
Didn't you buy the kit from him?

 

[Che_Guitarra]

My bad - I did buy the kit from Hairball, but just assumed these parts would be with the Mouser order. 

The Hairball kit is yet to arrive, but the Mnats PCB and Mouser orders have come in the last couple of days.  I'm too impatient to wait so i've started building up the circuit board!  I live in Western Australia and sometimes post can be real slow - it might be here in a week, or it might be another month... you never can tell.

 

[jplebre]

I honestly don't know how to match JFETS.
Mike ones seems to be tracking really well (they need to be matched for meter to track compression).

I'm sure the info to match them is available. You may find some on ebay?

Otherwise, Mike is your man!

But if you just click on "REVD with enclosure kit" the fets are included on the package you'll receive. Check your invoice

 

[Echo North]

My bad - I did buy the kit from Hairball, but just assumed these parts would be with the Mouser order. 

The Hairball kit is yet to arrive, but the Mnats PCB and Mouser orders have come in the last couple of days.  I'm too impatient to wait so i've started building up the circuit board!  I live in Western Australia and sometimes post can be real slow - it might be here in a week, or it might be another month... you never can tell.

Are you tracking it with the provided tracking?  It should take about 10 days to get to you.  If it's stopped moving for more than 10days (stuck at one point) you need to tell me so I can open a tracking investigation.

Thanks!

 

[Echo North]

My bad - I did buy the kit from Hairball, but just assumed these parts would be with the Mouser order. 

The Hairball kit is yet to arrive, but the Mnats PCB and Mouser orders have come in the last couple of days.  I'm too impatient to wait so i've started building up the circuit board!  I live in Western Australia and sometimes post can be real slow - it might be here in a week, or it might be another month... you never can tell.

Oh yes and FETs will be in the kit inside a bag with a Lola sticker and switch bank PCBs.

 

[Zackster]

Hi Again,

I just can't seem to get any change from moving the q bias trim pot. I have tested some of the voltages and the 30v at the side of r79 tests exactly as it should but many of the others I think are too high. G at q11 = -1.8 vdc    D at Q11=18.3 vdc and S at Q11= -2.3 vdc.  I am really unsure what to do because I thought that the voltages in this region would not read as they should until the unit is calibrated properly. The o adjust trimmer that is accessed in the front works as it should and I am sure that I am following the calibration steps properly. Do you have any suggestions? My only other concern at the moment is that the output knob raises the level as it should when being turned up but as it nears the max, it makes a bit of a clunk and enters a hiss zone. Maybe this has to do with the calibration, but I am unsure. Thanks for all your help!

Rich

I am having the (almost) exact same problem on the second channel of my build, although bypassing gain reduction does nothing for me. Adjusting r59 either way for  5 minutes shows no difference. The voltage on Q12 is

GR Off: D=17.7 V
GR On: D=9.5 V
VU:  D= 17.7 V
Q11 is also off (don't exactly remember the values), but all other transistors have correct voltages and +30V and -10V are as they should. On the succesfully calibrated first channel the voltage of Q12 is around D=9.5 V  for all switch positions.

The voltage behaviour in channel 2 is also quite random. It shifts when adjusting the other nearby trimpots, but resets when power is turned off and turned back on. Occasionally the voltage decreases on its own to about 12 volts (once even to 4V) when left on for a few minutes, but this is not constant behaviour. I would therefore imagine that Q11, Q12 and/or R59 is faulty. I can not think of an easy way to test these components in cirquit and would appreciate if someone with superior knowledge could share some advice. Otherwise I quess I will get replacement parts for all these components and hope I don't brake any traces.

Zack

An update;

1) replaced R59, no effect 2) replaced Q12 and Q 13, no effect 3) replaced Q11 and Q1, no effect

What I've found out so far: when the unit is powered on, the voltages at transistors are quite high. When measuring the base voltage of Q11 with respect to ground, the voltages decrease dramatically. I will attach a part of the pdf with voltages, provided by Mnats where I have made notes on the details. I hope it's OK to post it, but please tell me if not and I will remove it. This behaviour is independent of jumper Tp1 and knob settings. In fact it behaves the same with all leads (except output transformer, it is soldered) disconnected from main PCB.

To my understanding, no resistor could cause this and I have checked all transistors, caps and replaced the transistors with weird voltages. I am running out of ideas and would really appreciate if someone chimed in.

Zack

 

[jplebre]

Do you have any suggestions? My only other concern at the moment is that the output knob raises the level as it should when being turned up but as it nears the max, it makes a bit of a clunk and enters a hiss zone.

I had exactly the same, solved when I soldered neg side of C25 and attached to chassis (ground). There might be other thigns that could cause the same symptom but this would be a good place to start

When measuring the base voltage of Q11 with respect to ground, the voltages decrease dramatically.

Took me a while in JFets, the "base" is drain

Purely from what you are saying, I would say have a look at the voltages coming from the control. Also, did you do QBias adjustment?

no resistor could cause this

It can. Wrong value transistor will throw the voltage divider off and you will have weird resulting voltages.
I always check them before putting them in with a ohm-meter

 

[SonicWeaver]

Hi Folks

Just finished my first rev D build.  It fired right up with no problems and was calibrated per the vids. It sounds great and is compressing.

However when the unit's GR is on (makes no difference where the attack is set) and there is no signal at the input I can change the reading on the VU meter by a full db by turning the release pot.  So turning release from full CW to full CCW takes the meter from 0 to +1

Can someone tell me if this is normal or do I have a problem?

Thanks!
Gary

 

[jplebre]

have not experienced that.

 

[Echo North]

Took me a while in JFets, the "base" is drain

Base=Gate 

 

[Echo North]

Hi Again,

I just can't seem to get any change from moving the q bias trim pot. I have tested some of the voltages and the 30v at the side of r79 tests exactly as it should but many of the others I think are too high. G at q11 = -1.8 vdc    D at Q11=18.3 vdc and S at Q11= -2.3 vdc.  I am really unsure what to do because I thought that the voltages in this region would not read as they should until the unit is calibrated properly. The o adjust trimmer that is accessed in the front works as it should and I am sure that I am following the calibration steps properly. Do you have any suggestions? My only other concern at the moment is that the output knob raises the level as it should when being turned up but as it nears the max, it makes a bit of a clunk and enters a hiss zone. Maybe this has to do with the calibration, but I am unsure. Thanks for all your help!

Rich

I am having the (almost) exact same problem on the second channel of my build, although bypassing gain reduction does nothing for me. Adjusting r59 either way for  5 minutes shows no difference. The voltage on Q12 is

GR Off: D=17.7 V
GR On: D=9.5 V
VU:  D= 17.7 V
Q11 is also off (don't exactly remember the values), but all other transistors have correct voltages and +30V and -10V are as they should. On the succesfully calibrated first channel the voltage of Q12 is around D=9.5 V  for all switch positions.

The voltage behaviour in channel 2 is also quite random. It shifts when adjusting the other nearby trimpots, but resets when power is turned off and turned back on. Occasionally the voltage decreases on its own to about 12 volts (once even to 4V) when left on for a few minutes, but this is not constant behaviour. I would therefore imagine that Q11, Q12 and/or R59 is faulty. I can not think of an easy way to test these components in cirquit and would appreciate if someone with superior knowledge could share some advice. Otherwise I quess I will get replacement parts for all these components and hope I don't brake any traces.

Zack

An update;

1) replaced R59, no effect 2) replaced Q12 and Q 13, no effect 3) replaced Q11 and Q1, no effect

What I've found out so far: when the unit is powered on, the voltages at transistors are quite high. When measuring the base voltage of Q11 with respect to ground, the voltages decrease dramatically. I will attach a part of the pdf with voltages, provided by Mnats where I have made notes on the details. I hope it's OK to post it, but please tell me if not and I will remove it. This behaviour is independent of jumper Tp1 and knob settings. In fact it behaves the same with all leads (except output transformer, it is soldered) disconnected from main PCB.

To my understanding, no resistor could cause this and I have checked all transistors, caps and replaced the transistors with weird voltages. I am running out of ideas and would really appreciate if someone chimed in.

Zack

You've got a QBias issue.  The issue is it's not set correctly.  The voltages provided on the MNATS schem are for a FULLY calibrated unit.  If your QBias is not
set those voltage will be off.  The voltage at the gate of Q11 changes everything down the line.

You need to get your qbias working.  It's a very simple circuit (the qbias).

Have a look at pad 18 on the schematic.  It's the wiper of the QBias pot.  One of the outside pins on this trimmer goes to ground and the other is tied between to R's that make a voltage divider off the -10 rail.  So basically that wiper is pulling a neg DC from the divider plus some DC from pad 18 off the ratio PCB.  This neg qbias voltage then travels by wire through the attack/release network (see schem) and to pad then to pad 7.  Do you have a neg voltage at the wiper of the pot that changes?  If not something is wrong with R59, R35, R60.  If there is, but nothing at the Q1/Q11 gate, your ratio/attack wiring is bad.

 

[Echo North]

Hi Folks

Just finished my first rev D build.  It fired right up with no problems and was calibrated per the vids. It sounds great and is compressing.

However when the unit's GR is on (makes no difference where the attack is set) and there is no signal at the input I can change the reading on the VU meter by a full db by turning the release pot.  So turning release from full CW to full CCW takes the meter from 0 to +1

Can someone tell me if this is normal or do I have a problem?

Thanks!
Gary

Normal(ish).  Mine is more of a 0.5dB swing.