[BUILD] 1176LN Rev D DIY

[Rob Flinn]

Pad 21 d.c

20:1 -6.7
12:1 -3.8
8:1  -2.7
4:1  -1.8

Isn't pad 21 connected to the -10v rail via R54 ?  In which case would one not expect some d.c there /

Have to go out drumming now so will have to get to this when I get back

 

[Echo North]

Pad 21 d.c

20:1 -6.7
12:1 -3.8
8:1  -2.7
4:1  -1.8

Isn't pad 21 connected to the -10v rail via R54 ?  In which case would one not expect some d.c there /

Have to go out drumming now so will have to get to this when I get back

Yes you want DC there. You just need correct values and these look fine.

Head scratcher for sure...

 

[Rob Flinn]

I even swapped the main pcb out with another I had & it still happens ??

 

[Echo North]

I even swapped the main pcb out with another I had & it still happens ??

Well it's either a test procedure issue (with your scope) or something off PCB like your ratio/attack/meter network.  Maybe a hookup wire picking up noise somewhere?  Does the unit sound bad or can you hear an issue?

 

[Rob Flinn]

Thanks for your tips with this Mike. 

The thing is I have a sister unit to this faulty one & it is working perfectly.    With this unit if you inject a sine wave & turn the i/p up so it starts to compress the waveform rounds off at the top & starts to triangle at the bottom.

The signal is like this on the drain of the GR fet. 

 

[Echo North]

So you said both PCBs don't work in the one unit?  I assume both PCBs work in the other unit?

If that's so, it has to be an off board issue.  Which would mean bad component, damage/bad value component on the ratio board or attack release network, wiring maybe picking up interference....

That's all I can think off.  If the unit works in bypass I have a hard time thinking it would be the input tx, t-pad, or output tx.  I would think there is something wrong with the attack/release/ratio PCB.

Mike

 

[benlindell]

What is the fuse rated at?  Both of my units consistently popped T250mA during power up so I bumped to T500mA with no issues.  Others may say it's not safe, do what you feel is in your best and safest interest.

I think a 500mA slo blo is reasonable.  Some weird high toroidal in-rush I in that studio maybe?  You could try a new toroid (email me if you do).

I just put in a new Antek power transformer, it's powering up fine but the voltages are a little low, I'm getting +28V at the 30V test point and -7V at the -10V point. Is the transformer not powerful enough or do I have a damaged cap? I'm using a 25-0-25V 25VA transformer now.

 

[chipss36]

Just a thank you to all who worked on this kit, I look forward to the build, still reading this thread.
My first pro audio build , I have done a few tube amps , from the ground up and sure thank you all for the kit , all the hard work has been done here , again thank you.

 

[Rob Flinn]

Hi Mike

No, the spare pcb was a "spare" pcb, so I haven't tried it in anything else.  I tried swapping the GR fet with 5 or 6 spares but there is no difference.

Back to the work bench, keep you posted !

 

[Rob Flinn]

I connected the switch board from the working unit, & the faulty unit still has the same thing going on.  I've checked the wiring to the switch bank several times & it looks to me to be ok.

It appears that what it's doing is boosting the bass when the compression happens, or not compressing the bass end as much.

 

[dandeurloo]

I just put in a new Antek power transformer, it's powering up fine but the voltages are a little low, I'm getting +28V at the 30V test point and -7V at the -10V point. Is the transformer not powerful enough or do I have a damaged cap? I'm using a 25-0-25V 25VA transformer now.

I had one go bad right away once.  But it was intermittent.  So if I moved the wires just a little it would cut out completely. It was an internal problem.  So I pulled that and put a new one in.  Not sure that is your problem at all but they can be bad right out of the box.

 

[benlindell]

I just put in a new Antek power transformer, it's powering up fine but the voltages are a little low, I'm getting +28V at the 30V test point and -7V at the -10V point. Is the transformer not powerful enough or do I have a damaged cap? I'm using a 25-0-25V 25VA transformer now.

I had one go bad right away once.  But it was intermittent.  So if I moved the wires just a little it would cut out completely. It was an internal problem.  So I pulled that and put a new one in.  Not sure that is your problem at all but they can be bad right out of the box.

I'm getting 24.8VAC from the transformer so I don't think the transformer is the issue, hopefully.

 

[Rob Flinn]

problem sorted, wrong value ceramic caps the same on both boards !!

Blush!

 

[Echo North]

problem sorted, wrong value ceramic caps the same on both boards !!

Blush!

Awesome!  Glad you found it.

 

[Echo North]

I just put in a new Antek power transformer, it's powering up fine but the voltages are a little low, I'm getting +28V at the 30V test point and -7V at the -10V point. Is the transformer not powerful enough or do I have a damaged cap? I'm using a 25-0-25V 25VA transformer now.

I had one go bad right away once.  But it was intermittent.  So if I moved the wires just a little it would cut out completely. It was an internal problem.  So I pulled that and put a new one in.  Not sure that is your problem at all but they can be bad right out of the box.

I'm getting 24.8VAC from the transformer so I don't think the transformer is the issue, hopefully.

Could be a supply current issue but that tx should have plenty.  Is the whole board stuffed or just the PS section?

 

[Rob Flinn]

problem sorted, wrong value ceramic caps the same on both boards !!

Blush!

Awesome!  Glad you found it.

I knew it had to be something stupidly simple, unfortunately sometimes these things take a while to find .....

 

[benlindell]

I just put in a new Antek power transformer, it's powering up fine but the voltages are a little low, I'm getting +28V at the 30V test point and -7V at the -10V point. Is the transformer not powerful enough or do I have a damaged cap? I'm using a 25-0-25V 25VA transformer now.

I had one go bad right away once.  But it was intermittent.  So if I moved the wires just a little it would cut out completely. It was an internal problem.  So I pulled that and put a new one in.  Not sure that is your problem at all but they can be bad right out of the box.

I'm getting 24.8VAC from the transformer so I don't think the transformer is the issue, hopefully.

Could be a supply current issue but that tx should have plenty.  Is the whole board stuffed or just the PS section?

The whole board is built, it was functioning fine except it kept blowing fuses in the studio but not at my place, so with the new tx the power rails a low, is this possibly a supply cap issue or is it something further down the line drawing too much current. The previous tx that blew fuses had the correct voltages 

 

[sr1200]

was it blowing fuses in the studio because you were USING it? or was it just blowing with nothing going through it.  If the former is true, try sending some hot signals through wherever you're doing the build and see what happens.

 

[zekester]

I have been using my 1176 for a few weeks and have really been loving it. This morning, however, I shut it off and then an hour later no power. Fuse is good, but nothing past the switch. Anybody experience the meter switch failing on these?

 

[benlindell]

was it blowing fuses in the studio because you were USING it? or was it just blowing with nothing going through it.  If the former is true, try sending some hot signals through wherever you're doing the build and see what happens.

I was just blowing on power up apparently, it would last longer before it blew the longer inbetween power ups hence my suspicion that it's a cap related issue