[BUILD] 1176LN Rev D DIY

[Echo North]

Hi all - I'm building a REV D rotary version. All seems OK regarding voltages and I went through calibration OK. My problem is I have SO much gain! If I turn the output pot past 9 o'clock its audibly hissy.  It all seems in the output stage  - I'm using a 250k log pot. Is this correct for the rotary version? I haven't installed a trimmer on the ratio board - is that OK? Thanks

Sorry to ask again - I think my problem is also related to the fact that if I connect a 1k 0db signal to the input it suddenly drops to approx 0.25 V ! This happens regardless of whether the unit is switched on or off and even if i bypass the input transformer and T-pad. Any ideas? Thanks.

You loose 1/2 the signal in the switch from differential to single ended.

Have you checked your amp stage voltages against the MNATS schematic with voltages? 

 

[Spendor]

Yes i have checked all voltages on against MNATS and they seem within 5% or so. I have built two G1176's without an issue so this has me a bit stumped!

 

[Sillen]

Dual secondaries have NO 0V winding. This is only an indicator where a winding starts in respect to its other end. You have to read the complete sentence of the dedicated guide, IE follow the illustration from Mark Burnley or have a look at the datasheet for your transformer.
[/quote]

Well I obviously mean the wires of the transformer then not windings, thought it was the same.

Wired the primaries as described in its dedicated guide. Wired the secondaries 0volt windings to the centre of a screw terminal and the other two remaining windings to their own place in the screw terminal.

This is not at all what it says in the guide.

http://hairballaudio.com/docs/FETGUIDE/Section%20D%20-%20Power%20Section.pdf

Look at the images of the windings on the left of page 9.  Look at your Avel transformer windings.  Does that say to tie the "0V" leads together?

"Identify the two wires coming from the power transformer secondary that are closest to each other on the schematic. These are tied together to form the center tap. Twist them lightly together and secure them in the middle terminal of the terminal strip. Now take the two remaining secondary wires and attach them to either end of the terminal strip. The order of the top and bottom wires is unimportant. Just make absolutely sure you have tied the two "0V (centre tap)" wires together as indicated in Mr. Burnley's OUTPUT CONFIGURATIONS/SPLIT SECONDARY FOR +/- POWER SUPPLY illustration."

I did use mnats guide but it should be the same anyways. Here it very well tells me to connect the two 0v wires together in the terminal strip, doesn't it? I still wonder if the terminal strip could be the thing that makes the error occur?

 

[mnats]

Sorry to ask again - I think my problem is also related to the fact that if I connect a 1k 0db signal to the input it suddenly drops to approx 0.25 V ! This happens regardless of whether the unit is switched on or off and even if i bypass the input transformer and T-pad. Any ideas? Thanks.

I have built two G1176's without an issue so this has me a bit stumped!

Are you aware that the G1176 has a completely different input circuit to the Rev A to E? What is the output impedance of your signal source? What does your signal source do when you connect it to a 600 Ohm resistor?

 

[Harpo]

...Just make absolutely sure you have tied the two "0V (centre tap)" wires together as indicated in Mr. Burnley's OUTPUT CONFIGURATIONS/SPLIT SECONDARY FOR +/- POWER SUPPLY illustration."

I did use mnats guide but it should be the same anyways. Here it very well tells me to connect the two 0v wires together in the terminal strip, doesn't it? I still wonder if the terminal strip could be the thing that makes the error occur?

You have a dual secondary transformer, IE 4 wire ends, two for each winding coming out of your donut. There is no center tap per winding (that woud require a 3rd.wire) and both secondary windings are not connected, floating individually.
A transformer transforms an applied AC voltage in to an AC voltage out at a specific ratio. The dots at the transformers schematic symbol indicate, which wire is the in-phase/hot end of a primary and secondary windings end in respect to its other side for the same snapshot moment in time. This 0V or 25V RMS at the transformer drawing is only another way of indicating where the in-phase or out-of-phase winding end is located. Its a point of reference for measuring the floating voltage across this winding for the moment when the amplitude of AC mains is at max RMS in respect to the other windings end. This will be different or just the other way round again, depending on the snapshot moment of your local 50 or 60Hz AC cycle. When both of your secondary windings (2*25V) have the same primary:secondary ratio (115V+115V:25V+25V or 1+1:0.2174+0.2174 turns ratio) and you connect these secondary windings in series in their correct orientation, this will make these combined windings behave as a single secondary winding (115V+115V:50V or 1+1:0.4348 turns ratio) with a single in-phase/hot end at one side, an out-of-phase/cold end at the opposite combined winding side and a center tap in the middle of both combined windings.
This center tap connection is 0V in respect to both other winding ends of your now series connected secondary windings. This could be a single wire, if you join the secondaries at the transformer and take this junction to the center tap connection on pcb or you join both windings at the pcb as the instruction call these "the two '0V (center tap)' wires".
From the Avel Lindberg datasheet (the manufacturer of the transformer in question will know best what colour coding he used for wires going in/coming out) you would join the red+orange wires for your secondary center tap connection.

 

[Sillen]

From the Avel Lindberg datasheet (the manufacturer of the transformer in question will know best what colour coding he used for wires going in/coming out) you would join the red+orange wires for your secondary center tap connection.

On the transformer the black and orange wires are dotted and marked with 0V, those are the ones i put in the center of the terminal strip. However the black and orange wires are not next to eachother on the schematic if they were supposed to be?

 

[jplebre]

what you want to do is to put the 2 winding of secondary in "series". For that you need to us the in-phase+out of phase and tie them together. [24 -- 0+24 -- 0]

This will give you kind of like a 1 secondary with a center tap. One of the ac will be taken for the 30v rail, the other for the -10v

above was explained technically with great clarity and both Mnats, burnley and hairball's put this very clearly so not sure where exactly is your question.

 

[Harpo]

On the transformer the black and orange wires are dotted and marked with 0V, those are the ones i put in the center of the terminal strip. However the black and orange wires are not next to eachother on the schematic if they were supposed to be?

Last try.
RTF avel lindberg Y23 range datasheet.
The middle illustration figure shows how to connect the primary windings in series for your local 230V AC mains as well as the secondary windings connected in series.
This red+orange secondary winding ends are used for the center tap connection and are joined on pcb.
Just read the colour of the wires involved and hook them up accordingly, both primary side and secondary side.

 

[jplebre]

where are my manners, "... and harpo"

 

[Sillen]

Allthough wired correctly same error occurs (barely no voltage from secondaries). So why do you think this is happening? There is 237V AC coming into the primaries so the problem is not there. Bad transformer? Bad terminal strip?

 

[Echo North]

Allthough wired correctly same error occurs (barely no voltage from secondaries). So why do you think this is happening? There is 237V AC coming into the primaries so the problem is not there. Bad transformer? Bad terminal strip?

Check the DC resistance of each of your windings.  They need to be unconnected to anything else.

Blue/Grey
Violet/Brown
Red/Black
Orange/Yellow

The DCR should be real low.  I think the Primary windings are about 40Ω and the secondary are 4Ω. 

Mike

 

[Sillen]

Allthough wired correctly same error occurs (barely no voltage from secondaries). So why do you think this is happening? There is 237V AC coming into the primaries so the problem is not there. Bad transformer? Bad terminal strip?

Check the DC resistance of each of your windings.  They need to be unconnected to anything else.

Blue/Grey
Violet/Brown
Red/Black
Orange/Yellow

The DCR should be real low.  I think the Primary windings are about 40Ω and the secondary are 4Ω. 

Mike

Blue/Grey = 40.6 ohms
violet/brown = 41.4 ohms
red/black = 0 ohms
orange/yellow = 0 ohms

 

[Echo North]

Blue/Grey = 40.6 ohms
violet/brown = 41.4 ohms
red/black = 0 ohms
orange/yellow = 0 ohms

0Ω is actually impossible.  It's either something above 0 or infinity.  Even the wire in your test lead has resistance.  Is it infinity or are you only measuring down to 0.1Ω? 

 

[Sillen]

Blue/Grey = 40.6 ohms
violet/brown = 41.4 ohms
red/black = 0 ohms
orange/yellow = 0 ohms

0Ω is actually impossible.  It's either something above 0 or infinity.  Even the wire in your test lead has resistance.  Is it infinity or are you only measuring down to 0.1Ω?

My dmm wont even react when trying to measure them so I guess it's infinity then or high enough to outrange the dmm at least.

 

[Harpo]

...or the battery in your multimeter is low.

 

[Sillen]

...or the battery in your multimeter is low.

Wouldn't think so, it's a brand new fluke 177.

 

[jplebre]

if this is your transformer (and winding colour-code): http://www.avellindberg.com/transformers/y23_range_connections.htm

Then if you are measuring infinity on those windings something is not right ie. the secondaries are open circuit

There should be relatively low "omhage" between windings on their own sides, and infinite between sides (eg. primary winding to each of the secondary winding).

Seems to be damaged. I'm not sure how usual that is though Mike probably have better insight than I do.

Ensure trafo is completely disconnected when testing this.

 

[Echo North]

Ya disconnect it an re-measure those secondary windings.  Should be about 4Ω.  If it's infinity emails me.

 

[Sillen]

Ya disconnect it an re-measure those secondary windings.  Should be about 4Ω.  If it's infinity emails me.

Yeah they're infinity for sure.

 

[Mraihala]

Hello folks!

I just got my 1176 D working and calibrated. It seems to be functioning right, but every time I power it up the meter needle is +/- 1db from zero. Is there something wrong?

Thank you!

Mikko