[BUILD] 1176LN Rev D DIY

[Stagefright13]

The input transformer is a 2:1 for spec. Even using the 2:1 ratio you don't usually have to crank the input much. maybe your input transformer is wired backward as a 1:3?

 

[Underthebigtree]

There's no documentation for the Mnats input board, so I followed the traces under the board, and cross-referenced to the Lundahl pin info for the LL1540.

But this is very useful information. I haven't tried disconnecting the input board from the circuitry that follows and then measuring the voltage, wiring the signal out of the T600 to *either* side of the transformer, and see what ends up coming out the other side.

TommyP, I'll call ya. Let's definitely get together one day this Xmas break - the kids can play, and we can nerd out.

-np

 

[radiance]

Finished my 1176 today and after some fiddling around it all works.

My PEC attenuator pot attenuates only 8dB. Is this normal?
I wired it like this (this is not correct, read below...)

Can someone confirm if this is correct? It seems correct to me but it depends
on what the purple audio manual means with front deck and rear deck. I thought front deck is the one most close to the frontpanel right?



Edit: wiring diagram is wrong....should do more thinking ...

 

[radiance]

Anyone?

 

[mnats]

The image you posted looks exactly like the one neeno posted on page 29 of this thread that he said didn't work correctly.

Here's a scan from the Clarostat wiring sheet which is also a bridged T atten:

 

[Neeno]

Hi Radiance, the wiring diagram i posted is probably wrong...
I'm going to remove the file...

I found out how to wire it, but i didn't redrawn the diagram, i'll check it out tomorrow and make a new diagram...

 

[radiance]

Thanks all!

 

[Nadege]

Hello,

I've got exactly the sme issue as Radiance. Did you found some time to redraw the Bridge T attenuator wiring?

thanks

 

[mnats]

[quote author="Nadege"]Hello,

I've got exactly the sme issue as Radiance. Did you found some time to redraw the Bridge T attenuator wiring?

thanks [/quote]
What's wrong with the drawing I posted above?

 

[Nadege]

Hello,

Mnats, Thanks for this drawing but unfortunatly, I just can't read it. Don't know why but the image on my computer is really blurry... :?

Neeno told radiance he was going to redraw it's wiring and I was also waiting for this.

Thanks a lot for your help

 

[Neeno]

Ok guys... sorry but i was pretty busy... we had 60cm snow this night...
I love this country ! ahahah

This should work, it's the way i connected my t-attenuator...

Check it, try it and post back please !
Cheers

 

[radiance]

Neeno, that is exactly what I made of the pic Mnats posted and it works :grin:

 

[Neeno]

That's great ! :thumb:
Thank you !!! :grin:

 

[tommypiper]

Just wanted to offer a quick update. Underthebigtree got his working on New Year's Eve when we did a systematic check and diagnosis. (We found nothing wrong after he had already sorted some grounding.) He ran some drum mixes through it. It Sounds Great. I'm sure he'll post when he gets time.

Meanwhile, I'm still wiring mine during rare kid-free moments... Was doing some unusual configurations which puzzled me for a while. H pad instead of T pad. Stereo in one box with one meter. Figuring out stereo link options, different PSU options, different Lundahl iron, Neve iron, etc... more later.

 

[Nadege]

hELLO

I've been working ahrd these last days to finish a dual 1176 Rev D using Mnats PCB and ed's transformers (altran input and cinemag output)

Got one channel working fine but not the other one.

I've been thru all the usual test, bring in my oscilloscope and found something quite strange...

When I'm applying a sine (1.000kHz) to both input and tracing the signal, I have exactlt the same signal up to the input of the altran (changing with my input PEC bridged T attenuator position. BUT after the altran , the signal is 2 time softer on the "non working properly" channel.

Is it possible I solder the altran the wrong way? I put both of them with the sticker facing the same point . Is it possible the sticker on one of the transformer was sticked at the wrong place ??? :? :? :? :?

The problem is there, but Im a bit lost...

any idea

I'll try to post pictures asap

Thanks :sad:

 

[Nadege]

hello

I've wired the altran the other way and it seems to be ok now.. Still have a burned transistor on the output stage to fix.

 

[Miska]

Hello!

I'm soon going to start building a dual version of the rev D.
I'd like to know how many of you built this in 1RU rack case? Or was it only Mnats himself who did it? Did you meet any issues afterwards that were caused by the 1RU installation? Hum, noise etc.. Would you recommend building in 1RU or not?

Let me know your opinions!

Thank you,
Miska

 

[kato]

The VU meters are the biggest issue.

If you can find VU meters that fit in a 1U case, and don't mind removing the endbells from the output transformer - you can fit it in 1U.

You'll make life a little easier for yourself if you use 2U.

 

[Nele]

Any chance of a new pcb-run?

cheers,
c

 

[buschfsu]

also interested in a run...

just finished a rev g and would like to start a rev d

thanks