All things G1176 - the new "repost" thread.

[keefaz]

Just in case, check if pin 18 in the main board is connected to
the QBias trim pot (R81) wiper.
With some trim pots, you have to make a jumper here

 

[W DeMarco]

Slow down Buddy,

Dont tear your hair out, it won't help your 1176, don't speak to it either, it won't hear you.

I would check all those interconnects and make sure their going to the appropriate spots. If your using the MNats board there are 2 hole 18's wich accomodate different size trimmers directly next to it. I was plugged to the wrong hole 18, this played havoc with me for a few weeks. My G acted horribly until I plugged her to the right hole. Now its in a rack at the studio!!

It sounds like a bad connection to me. Make sure your pcb is elevated enough not to ground on the chasis as well.

Will

 

[glide 1]

Hi all,

I have built 2 of Mnats' board using OEP A262A2E trafos on both, a little coloured but generally happy with them. I've got 2 more almost fully stuffed and i'de like to use a different trafo for a different "flavor".

I recently emailed Joe at JLM asking him if i could use his JLM111DC on the output and this is his reply:

Our JLM111DC on the output of the 1176 will make a huge difference allowing heaps of headroom and cleaner pure tone instead of the distortion and unbalanced tone of the A262A2E which cannot handle pro level output at all.

So i decided to try this out..

http://www.jlmaudio.com/JLM111DC_Output_Transformer.htm

Can someone please tell me how to wire this up to the board. I think i've got the secondary output pads on the JLM ok going to the output XLR but i'm not sure which pads to use for the input to the primary of the JLM111DC.
I'm thinking pad "(1)" on the mnats board comming from the negative leg of C15 (the 470uf capacitor) to "+1" on the JLM trafo primary (marked "+ out BA" on the JLM pic above) can someone confirm this please. Thanks in advance


glide 1

 

[mnats]

glide 1,

That's correct - with my boards the pad marked 10 and (1) [parenthesis denoting the 2:1 configuration] of the Lundahl LL5402 footprint or S1 of the OEP primary is output of the line amplifier. If you use Jakob's Rev 7 boards use Pin 1 of the Lundahl footprint. Be sure to hook up the transformer's primary to the ground as well. It looks like the -1 pin on the JLM transformer is ground.

Find out from Joe what load resistor, if any, his transformer requires. The G1176 boards upon which mine are based have a resistor, R84, that sits across the Lundahl secondary. This might not be necessary or may need to be a different value for the JLM transformer.

Depending on how you have wired your unit, you may want to return the transformer secondary to the board. If you have wired it as per normal the X and Y pads go to the meter board. Without the secondary connected to the board you will lose your output metering function.

Return the +2 on the JLM to pad 5 of the Lundahl footprint and -3 of the JLM to pad 2 of the Lundahl. This will ensure your meter works correctly. You can wire the output XLR to the BAL OUTPUT pads on the board as normal.

Seems a pity to use a gapped transformer here since no DC gets through the output capacitor, but please let us know how it works in this application when you get it going.

On a side note, have you had any problem with the output levels of your first two units? Joe had mentioned this in another thread but I wasn't too clear on what his criteria was...

 

[glide 1]

Hi Mnats,

Thanks for the reply.

Find out from Joe what load resistor, if any, his transformer requires. The G1176 boards upon which mine are based have a resistor, R84, that sits across the Lundahl secondary. This might not be necessary or may need to be a different value for the JLM transformer.

I will email joe about this, it will be a week or so befor the trafo arrives but i'm eager to try this based on what he said.

Depending on how you have wired your unit, you may want to return the transformer secondary to the board. If you have wired it as per normal the X and Y pads go to the meter board. Without the secondary connected to the board you will lose your output metering function.

1:2 was recommended by joe. I have taken note of this too, did not think of the X and Y pads for metering.

Seems a pity to use a gapped transformer here since no DC gets through the output capacitor, but please let us know how it works in this application when you get it going.

Can you explain this further, i'm not sure what the difference is with gapped transformers. The "headroom, clear tone, and less distortion" part of joe's post is whats making me curious.

On a side note, have you had any problem with the output levels of your first two units? Joe had mentioned this in another thread but I wasn't too clear on what his criteria was...

I have'nt had any problems with output levels per se but the output pot is almost always at the 3 'oclock position, and more sometimes, to get decent levels to my converters.

I also read that post from joe somewhere saying that the OEP A262A2E saturates very easily. Not sure but he mentioned something about that it is because of its physical size that it distorts easy thus giving that percieved color, having less headroom and so on..

I will definitely post comparisons here when i get everything going.


glide 1

 

[Guest]

DeMarcoand keefaz -thanks for your help - it turned out to be a faulty Lorlin rotary on the meter board - prevented the signal continuing over to the ratio board when i GR mode - think I overheated it when i was soldering. So I have 2 1176's in one 2U rack working - and sounding fantastic - going to tidy up some of the wiring.

I'm using Mnats PSU and the -10v regulator gets very warm (i have a small heatsink on it) it hasn't shut down but it's very hot. i'm using the -10v rail after the regulator to power 4 relays for True bypass.

I'm using four omron relays for true bypass and the combined power draw of these is 4x 280mw = 1,12 watt. P=IV so current draw should be I=P/V = 1,12/10 = 0,11 amp. i have a big 50va 24 - 0 -24 torroid. This shouldn't be a problem should it?

/Taz

 

[gyraf]

i'm using the -10v rail after the regulator to power 4 relays for True bypass

Don't do that.

That is about the worst place to draw extra current.

Better to use 48V relays (or coils in series), and power it from the +30 before regulation (there will be some 35-40VDC there)

Jakob E.

 

[Guest]

Ok - i'll try powering them from before the regulator.

/Taz

 

[ChrioN]

On page 1 of this thread, a working 1176 had the following measurements:

Q8 14.01 14.61 30.29
Q9 13.94 13.33 0.002

I got this:

Q8 13.61 29.88 14.22
Q9 13.52 0.001 12.92

Is it possible that I've soldered those two transistors in reverse?

 

[King_Cruiser]

Index Thread>Meta

 

[ChrioN]

It seems that I've forgotten to solder on the two jumpers, the short ones "behind" Q8 and Q9...Actually, I saw them for the first time right now. hehe.

Ok, now the jumpers are in place. No difference, just some slightly higher voltages on all pins of Q8 and Q9.

 

[ChrioN]

Should I have ~10vDC at pin 2 and 3 to ground on the xlr input? wtf I'm going insane...

 

[Rob Flinn]

[quote author="ChrioN"]Should I have ~10vDC at pin 2 and 3 to ground on the xlr input? wtf I'm going insane...[/quote]

No, you shouldn't ! Both input terminals are connected to the rest of the circuit by capacitors which should block any voltages to the input XLR. This suggests that you have a short somewhere.

Also have you connected your i/p XLR to the right terminals for the transformeless i/p.

 

[ChrioN]

I've scratched the back of my head so much, there is a big hole in it now. Luckely I got a calming phone conversation, from a forum member, just in time :green: :thumb:

Could it be that I've added some of the *-components? Its not (I think) the ones used for the input transformer option, its the ones Mnats says this about: (quote) The components marked * on the board are optional components not included in the original unit or schematic.

Here is a pic:

Any clues?

 

[mnats]

Surely the problem is more likely to be on the solder side of the board. We (and you) would probably know more by having a look there...

 

[ChrioN]

Every pin on IC2 (NE5532) has 15vdc except 4 and 8 (pin 4 is ground, 8 has 30vdc).
Ain't that pretty wierd?

They don't short when power isn't applied.

Looking at the schematic, only pin 5 and 3 should have 15vdc (30vdc from the power supply, through the 100kohm voltage divider)

I've also noticed that there is a second "E" hole next to the ordinary "ECB" on Q9. Should I move Q9 a step and try using the second "E" hole instead?

 

[Rob Flinn]

[quote author="ChrioN"]Every pin on IC2 (NE5532) has 15vdc except 4 and 8 (pin 4 is ground, 8 has 30vdc).
Ain't that pretty wierd?

They don't short when power isn't applied.

Looking at the schematic, only pin 5 and 3 should have 15vdc (30vdc from the power supply, through the 100kohm voltage divider)[/quote]

Maybe the NE5532 is duff !

 

[ChrioN]

One problem is gone: every transistor DO measure right. I might have had solder smoke poisoning last night, and messed up the values...because now they are all good. (and most definentely was all the time...)
The thing that made me measure again was, that according to last nights measurements, I would have tons of vDC at ground, which I knew I didn't have.

Still, I got issues with the ~12vdc at the xlr input, which seems to be connected with the wierd NE5532 readings...
I've switched ne5532 but I get the same readings

Tips? (and thanks you guys for all the help so far)

 

[ChrioN]

I replaced both input caps (better ones, BC), but I still get ~12vdc at the input xlr (pin 2 to ground and pin 3 to ground) It drops slowly, 0.1vdc per 20 seconds or so. Its not "stable" at all.

No shorts between the both soldered legs.

I think this seems impossible. Rule number one is that a (working and healthy) capacitor doesn't allow dc voltage flowing through it. :?

Its like Ethan Hunt is staring this mother.. :green:

I've taken a pic, but the flash of the camera makes the "solderblobs" look like crap, which they ain't.

 

[gyraf]

It drops slowly, 0.1vdc per 20 seconds or so. Its not "stable" at all.

My guess it that once you've connected something to the input, the DC will go away. What you see now is input capacitors discharging through your voltmeter..

Jakob E.