[BUILD] 1176LN Rev D DIY

[Commander Fluffypants]

Ugh. This going to take a few posts. Sorry about the spam.

 

[Commander Fluffypants]

Whole thing

 

[Commander Fluffypants]

Pots

 

[Commander Fluffypants]

More pots

 

[Commander Fluffypants]

Board

 

[Commander Fluffypants]

Meter area. I've got more and can take more if there's something you'd need to see more clearly. I figure I've spammed this thread pretty hard for one night.


I did some searching a few days back and now I can't seem to find what I had found, but someone somewhere mentioned disconnecting the shielding from on end of the audio path. Would that mean removing the wire connecting the xlr pin to ground at  the output?

As always, thanks!

 

[Commander Fluffypants]

Argh.

While I had the thing open, I decided to clean the main pcb. There was flux on it and I cleaned it up a bit. It still hisses, maybe even louder.

The hum goes up and down with the input control. The hiss comes on when the output control gets to about 48 and stays level until the output goes above 12 and then it gets louder as the output goes up the rest of the way. The hum is soft. The hiss is loud.

While I was messing around with it, I tried to connect it with the top and bottom panels off. Very loud hum. This was cured when I put the panels back on.

Hopefully this information means something to someone.

Thanks again.

 

[Commander Fluffypants]

Oh yeah... one other detail... when I power the unit off, if it's still plugged into the system, speakers on, etc., I can hear a discharge hiss. Does this point a problem with caps or transistors? Everything seems to be in order on the pcb; correct placement, orientation, etc. Ground wire from power cap to back panel is in place also.

 

[core64]

Pardon me if my posting protocol is off a bit as I'm new to the forum...

I just completed the steps in building the PSU for the Hairball 1176 Rev D.  I've been following the instructions by the book ( I think), and triple checking each step as I go. 

Before moving onto the next step, I was checking the voltage readings for R87 (+30V) and  CR6 (-10V) .  According to the instructions, my readings should be within +/- 5% percent of these readings.  The readings I'm getting are as follows.

CR6:  -9.05
R87:  +28.14

As you can see, I'm a bit over the allowed threshold for each.  My question is...  Are these readings still acceptable, being there only slightly over, or does this indicate a problem?  If so, any clue as to areas I should focus on?

Thanks in advance!

k

 

[Echo North]

Pardon me if my posting protocol is off a bit as I'm new to the forum...

I just completed the steps in building the PSU for the Hairball 1176 Rev D.  I've been following the instructions by the book ( I think), and triple checking each step as I go. 

Before moving onto the next step, I was checking the voltage readings for R87 (+30V) and  CR6 (-10V) .  According to the instructions, my readings should be within +/- 5% percent of these readings.  The readings I'm getting are as follows.

CR6:  -9.05
R87:  +28.14

As you can see, I'm a bit over the allowed threshold for each.  My question is...  Are these readings still acceptable, being there only slightly over, or does this indicate a problem?  If so, any clue as to areas I should focus on?

Thanks in advance!

k

Seems fine. 

The readings are always a little lower.

 

[core64]

Seems fine. 

The readings are always a little lower.
[/quote]

That's great to hear that!  Thanks very much for your reply!!

Kenny

 

[dbonin]

Oh yeah... one other detail... when I power the unit off, if it's still plugged into the system, speakers on, etc., I can hear a discharge hiss. Does this point a problem with caps or transistors? Everything seems to be in order on the pcb; correct placement, orientation, etc. Ground wire from power cap to back panel is in place also.

Did you compare voltages to mnats "calibtared" voltages?  That may help point to something.

 

[Commander Fluffypants]

Thanks again, Don. Do you mean the voltages here: http://mnats.net/files/1176REVD_VOLTS.pdf ? You mean it's time for me to figure out how to read a schematic? Cool. I might be ready.

Do these symptoms point to anything that might narrow down my search?

 

[meandillar]

Hi all,

I completed an Mnats Rev D 1176 about 4 or 5 years ago and it has been working fine up until recently. It is passing signal and is compressing but the signal is thin, lacks any bass and is a bit distorted. Visually everything looks fine inside and I've done a wee bit of poking about with no success.

I shifted overseas and didn't bring any of my test equipment but I was hoping that on the off chance someone here would recognise these symptoms as a typical fault they have come across before. If not I'll take it to a tech.

If anyone has any ideas about what it could be I'd appreciate it greatly.

Cheers,
Dean

 

[dbonin]

Thanks again, Don. Do you mean the voltages here: http://mnats.net/files/1176REVD_VOLTS.pdf ? You mean it's time for me to figure out how to read a schematic? Cool. I might be ready.

Do these symptoms point to anything that might narrow down my search?

Yes that's the one.
Checking voltages may help narrow it down.    The components are labeled on the schematic the same as they are on the PCB so it's not too bad to hunt down the parts and check they as close to the values he has laid out in the document.

 

[Floti]

Hi! First of all thanks for being able to build this! The build was always clear and easy, I enjoyed it!

I just finished building my unit and I was having a hard time trying to calibrate de GR meter. Then I realised that when I switch the attack on or off, randomly, it stops working. I'm reading at the output 2,44 VAC with attack off and 0,775 with attack on, but to get those readings I need to switch the 1176 on and off a couple of times until the attack pot decides to act normally again. If I go from Attack off to on or from Attack on to off while the 1176 is plugged on, then I stop having those readings and my DMM reads 0 VAC or something close to it. That means, somehow, the pot stops reacting when going from on to off. 

I wasn't sure if that was a problem of my DMM or the 1176, so I passed some music through it and it seems to compress and sound good. When I turn attack on/off the it starts acting crazy again. Also when I change the ratios, sometimes it acts as expected, but sometimes some of the ratios lose a lot of gain or sound funny. It's also random. It may happen with any of the ratio configurations.

I inspected connections and solder points and checked for continuity here and there and can't seem to find the problem. Do you have an idea of where should i be looking at? I guess some short in the pots, maybe I should rewire them again, but I checked and there doesn't seem to be a short. Also my power supply was checked before and after and is fine.

Thanks in advance!!

 

[Floti]

I found out one of the legs from the input transformer wasn't properly soldered and the vibration from turning the attack pot on/off made it randomly work/not work.

Now my Q bias isn't changing the output voltage at all, but I've seen there's a post that should help me with that. I hope I can figure this out!

 

[Commander Fluffypants]

Once again, I'm going to ask a face palm kind of question... but every time I do, someone helps me out and I learn something.

I've been staring at the schematic and I've even been searching the web and reading at least one book to learn how to read the schematic. I can now look at the schematic and identify the corresponding parts on the board, and, thanks to the book, I even have a vague idea of what the parts are doing and why they're in the sequence that they're in.

But what I still don't know is simply where to jam the multimeter to check for the voltages. For instance (schematic here: http://mnats.net/files/1176REVD_VOLTS.pdf) if I was to try to test the voltage going into Q4 on the Signal Line Amp from C8 (that's the base, right?), I would put one of the leads (oh... and does it mater which one? Are you face palming already?) at the center leg of Q4 and the other one ... where? And then to test the voltage going into the collector of Q4, where on the board do I put my leads? And going out? It also seems that when I do this, I should do it from the underside...? It's not like I'm going to have an easy time sticking a meter lead under some of these things.

I did do a search here and on the web and found so much about where to test certain kinds of components, but not how to actually or where to actually place my MM leads. If you know of such a resource, I'd love to see it.

As always, thanks.

 

[Echo North]

Once again, I'm going to ask a face palm kind of question... but every time I do, someone helps me out and I learn something.

I've been staring at the schematic and I've even been searching the web and reading at least one book to learn how to read the schematic. I can now look at the schematic and identify the corresponding parts on the board, and, thanks to the book, I even have a vague idea of what the parts are doing and why they're in the sequence that they're in.

But what I still don't know is simply where to jam the multimeter to check for the voltages. For instance (schematic here: http://mnats.net/files/1176REVD_VOLTS.pdf) if I was to try to test the voltage going into Q4 on the Signal Line Amp from C8 (that's the base, right?), I would put one of the leads (oh... and does it mater which one? Are you face palming already?) at the center leg of Q4 and the other one ... where? And then to test the voltage going into the collector of Q4, where on the board do I put my leads? And going out? It also seems that when I do this, I should do it from the underside...? It's not like I'm going to have an easy time sticking a meter lead under some of these things.

I did do a search here and on the web and found so much about where to test certain kinds of components, but not how to actually or where to actually place my MM leads. If you know of such a resource, I'd love to see it.

As always, thanks.

You're testing the DC bias at various points in the circuit so to start you want your DMM to test DC volts.  Next you need to use the common lead and attach it to common somewhere.  I'd use the middle terminal on the main PCB power connection which is your power ground.

If you're not sure what the Transistor leas are down load the transistor data sheet.  It'll show you.  You can double check by looking at the schematic then following the traces on the PCB.  Once you know where you want to test put you test lead (red) on that transistor leg.

Mike

 

[Commander Fluffypants]

Thank you, Mike!