[BUILD] 1176LN Rev D DIY

[ILOVE1176]

Thanks so much for your quick reply Edward. Its appreciated. I will definately reread the info over at hairball more carefully.

So im using my 2N3708 to stuff my 2N3707 spots on the board. thanks for confirming.

I re-edited my post regarding my missing 1k trimmer........ Im not sure about that still.

I found the info regarding R12 Value should be 1.8k rather than 920 but i still wanna confirm if R4 is simply a 270 ohm resistor as at position R41.

kindest regards

 

[pittsburgh]

I just put my power supply together. I double checked for mistakes but didn't find any. Anyone see anything I missed?

 

[pittsburgh]

2nd Image

 

[pittsburgh]

Ok, I'm blowing fuses @ the IEC so something isin't right in the wiring of my power transformer. Here's what I've done:

Hot from the IEC connector goes to blue and violet, Neutral is wired to gray and brown. This is the reverse of the Using the Avel-Lindberg 2X25 30VA Dual Primary/Secondary Toroidal Power Transformer page, http://mnats.net/1176_reva-d_hairball_wiring_power_avel-lindberg.html, but seemed appropriate as the windings for the PT start with blue and violet as indicated by the picture I've put up. Do these need to be switched?

 

[Stagefright13]

Your blue and violet together and  the brown and grey together are correct for 110 volt mains.

Then tie the small black and orange wires together for the center position on the board. The remaining yellow and orange to the outer posts on the board.

Be VERY careful with Mains Voltage!!!!!!!!!!!!!!!!

 

[pittsburgh]

Stage, that's what I'm doing. So if that's wired correctly what else can I check?

 

[Stagefright13]

I would triple check the caps are in right and diodes. Also that Tantalum 6.8uf ya got there should be an electrolytic. What size fuse are you using. Is it A slow blow?

I don't see the orange and black wires tied together from the pics. (The Center Tap) Where is the black transformer wire going to?

 

[pittsburgh]

All caps and diodes have been checked with the schematic and are correct. Lines for the secondariness are connected to a terminal. They are not twisted together currently.

  I am using a .35 amp fast blow fuse. I was shipped a .25 amp with the materials, but couldn't get that exact value earlier this afternoon.

 

[Stagefright13]

Hmm obviously something is shorted. Check you eic jack they can't handle much heat when soldering. Also disconnect the tranny from the screw terminals too to isolate it that it is indeed the board...

Also look VERY carefully for A solder bridge on the underside of the board. And those tantalum caps are polarized also with A tiny stripe.

 

[pittsburgh]

I've got audible continuity on all three terminals of the IEC jack when checking from the back to the front, no shorts on the bottom of the PCB anywhere. I tested with the power transformer not mounted to the case and blew the fuse on the IEC just like last time.

What are the chances that my power transformer is faulty? Should I try wiring that independently of the rest of the build just to see if I get the right secondary voltages?

 

[Stagefright13]

Yeah start from the cord and work your way in adding one thing at a time. I would check the transformer. I have never had A bad one tho bought lots of 'em. Did ya disconnect the output wires of the tranny from the screw terminal block? I would try that first.

 

[Echo North]

Inrush current can easily be more than .35A.  If it's a fast blow, make sure it hasn't blown.

 

[Stagefright13]

That's true. I use 50VA torroids in mine so even 1/2 amp fuse will blow instantly.

 

[spase]

becouse here i cant find 2x25 30VA transfomers i just can get 2x24 50VA transformer

 

[pittsburgh]

Is the fuse too small then? Should I try 500ma or even a 1amp?

 

[Stagefright13]

I don't want to tell ya to use A bigger fuse. But I have 1 amp fast blows in all mine with my larger transformer. IF it were me I would! The 500 ma should still blow right away if something is wrong.
But really A slow blow is what is specified.

And Spase that 50 va should be just fine.

 

[spase]

even with 2x24 right?

 

[Stagefright13]

I am using 30x30 50VA on all of them. With 1 amp fast blow. I would "Think" 24x24 would be ok. Maybe someone else can chime in.

John

 

[Echo North]

Is the fuse too small then? Should I try 500ma or even a 1amp?

Definitely don't do that.  The fuse is there to protect your circuit if anything goes wrong and is wired wrong.  Using a fast blow large enough not to blow when the unit is turned on (when inrush happens) would be unsafe IMO.

I'm not sure where you are located (pittsburgh?) but places like radio shack have 1/4 amp slow blows.

 

[Echo North]

I think 2 X 24 would work.