All things LA2a related

[Purusha]

OK, a few more questions: :grin:

How do I wire the meter select switch?

P123 top
P123 bot

Mine has only +4 and GR option. Switch is dual ON/ON toggle.

And I still have no idea how to wire Sowter iron to the board. On the board is info screened for the original iron and not for the Sowter.

Thanks Sintech for the info though, it helped a lot.

 

[dripelectronics]

lemme pull some files togeather ,
ill post in an hour.

g.

 

[dripelectronics]

 

[dripelectronics]

for the meter switch

not using -10

is as such if looking at the back of switch.

2 p 3 top

2 p 3 bottom

the 'p's go in the middle

sounds wierd ,
i know .

g.

 

[Purusha]

Thanks Greg,

So 3 ground points are on the board?
And we have one star ground on the chassis plus Hammond is grounded to the screw where it's mounted. Did I understood this right?

What about the Hammond wiring? Can you check this too?

 

[Purusha]

I just found this picture :razz:

OK, to confirm if I understood this right.

1. All the GND tags go to the chassis as close as posible to the board?

2. I cut off the rest of the Hammond wires which are not used?

3. If fuse is used in the IEC, I just jumper the fuse section on the board?

 

[emx]

Anyone here have a good high-res copy of the 1968 schematic? I've looked on cayocostas site as his layout is what I'm working with, and I believe he is working with the 1968 version. The schematic on his site is a little hard to read on V4 Pin 5 but it looks like it's 120 or 130.

 

[emx]

Another Question, on the schematics that have the 22k R34, is R38 used at all? I'm looking at a schematic in front of me that's a different version than th 1968 one that uses the 22k R34 and it shows absolutely no R38 so far as I can see, just a straight shot to the filter caps.

 

[The Kid]

Another Question, on the schematics that have the 22k R34, is R38 used at all?

About 20 pages back (out of the 105 pages of this thread) this is covered at least twice. :wink:

 

[Purusha]

OK, everything at it's place :grin:

what next? :roll:

What is the safety procedure? No tubes and T4B and measuring the tube sockets or what?

What current should I see coming back from the Hammond? I would like to measure if this thing works OK?

I did power up the unit without the tubes and T4B. Should I see the meter light bulb burn at this stage or not?

I am new to the LA-2A build so please help me out with all caution instructions :razz:

 

[dripelectronics]

hey there , happy cristmas.

i usually just flip the switch and duck.

the fuse will save you if any thing is wrong.

usually leave the t4 out to start.

on the hammond ,

ive never wired up a european one ,
so im a bit unsure .

did you have a center tap ?
otherwise youll have to put some resistors to ground and to each leg of the heaters.

the neon will light up with a turn of the zero adjust/

good luck ,

g.

 

[Purusha]

Hi Gregory,

Can you please check the PDF of my Hammond 369JX - http://www.hammondmfg.com/pdf/5c0028.pdf

I will not try to power it up with tubes until someone confirms the wiring on my Xformer :?

I bought it here
http://www.tubetown.de/ttstore/product_info.php/info/p442_Hammond-369JX.html
and I really don't know if it's center tapped or not. Someone gave me this link so i bought it.

 

[matta]

I really don't know if it's center tapped or not.

Purusha,

If you look at the datasheet you will clearly see that it is. Look under the the 369JX info and you will see the Filament #1 is CT (which stands for center tapped) 6.3VAC.

On the 369JX the extra wires you see are the MULTIPLE primaries that the transformer has because it runs at 100, 110, 120, 200, 220 and 240 VAC.

If I read the datasheet correctly the wiring on the secondaries is as follows.

The High Voltage will be RED and RED, just like the Allied and Greg's info with a RED/YELLOW CT which goes to the chassis.

The Heaters/Filament or the 6.3VAC wires are BLACK/YELLOW and go to the LA-2A PCB marked as GREEN, the CT is orange and again that goes to the chassis just like the RED/YELLOW one (Having seen a pic of the trano i can see the datasheets is wrong as the filament is colour coded from filament #3 not one, being GREEN and GREEN witah GREEN/YELLOW CT).

I think your operational voltage in Europe is the same as ours, being 240VAC (well ours is actually 230VAC), in which case you would need to configure it as such.

In order to do this you would have to put the primary windings in SERIES with each other.

To do so connect the BROWN and the BLACK wires together (120VAC + 0V)

Then your mains wires would be the BLUE wire and the WHITE wire.

So the wires that are not connected would be the BLUE/YELLOW, BLUE/BROWN, BLACK/RED and WHITE/BLACK, these must be insulated with some heat shrink and taped up.

I would advise you DON'T cut them as one day you may want to change the primary voltage if you find yourself overseas, and would have the flexibility to do so.

I would NEVER blindly just follow the datasheet. I would test the transformer windings with a multimeter BEFORE just hooking it up to the PCB because you may have a problem with an incorrect winding that could damage your LA-2A.

So mount it in the box and make sure you ground the center taps and throw the switch and measure your secondaries. You should get over 500VAC across the RED HV wires and over 6.3VAC the BLACK/YELLOW wires... I say over as all unloaded AC tranos SHOULD be over the loaded voltage, I forget the % and math behidn it.

I hope that helps you out, enjoy your Christmas!

Cheers

Matt

 

[dripelectronics]

thanks matt ,

wasnt sure how to do that.

best

g.

 

[matta]

Hey Greg,

No worries! I think I got it all down right, but someone can over look my writings to make affirm it.

Sadly Purusha was a bit heavy handed with his wiring and didn't check the datasheet, which I have warned him against as these are not Micky Mouse voltages, and they can KILL you!!!

Below is a pic of how I take it it should be wired up as, in the CORRECT section, sadly Purusha had it wound like the INCORRECT side.

He has since corrected it to my wiring diagram, but now he is getting noting out of either the HV or Filament secondaries :-(

Could he have toasted the transformer? Maybe CJ or one of the more 'advanced' trano guys can answer because I don't know and as I think my wiring guide is correct, I can't account for it NOT working.

Is there another way to test to see if it is working or the fault lies elsewhere?

Cheers

Matt

 

[Purusha]

I guess CJ hasn't seen my PM yet :green:

 

[CJ]

Lordy, for a while there, it looks like you had a neon pwr supply.

12 times 300 is 3600 volts!

Ohm out all the windings with the wires un soldered and report back immediately.

 

[Purusha]

Hey CJ, I am on it :wink:

 

[Purusha]

OK, here we go:

Let me know if I missed something.

 

[CJ]

Your cool.
Put in a new fuse and let er rip.
Pull the tubes first.